Short-stay 29ers- the limit?- Mtbr.com
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  1. #1
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    Short-stay 29ers- the limit?

    I have a dreambike: a 29er with 16" (or even shorter) chainstays.
    I am not an expert, but think it is possible.
    The (factory-produced) Nimble 29er has 16.5" chainstays.
    Chris Igleheart said he could get the stays down to 16.2".
    I have seen fat-tire 26" trials bikes (= 27" real rear wheel diameter) with 15" stays and shorter.
    What, really is the absolute minimum on a 29er if we pull out all the stops:
    -83mm or wider bb shell to push the cranks away from the frame; corresponding rear hub
    -ditch the front derailleur if necessary
    -chainstay yoke
    -seat tube shifted forward
    How low can we go?
    _

  2. #2
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    I'll say you're looking at 15-1/4" minimum with about a 2.0" tire.

    Wheel radius of about 14-1/2" plus the BB radius of 3/4". Of course, that will net you with about 0 tire clearance. You could have more clearance or a shorter chainstay with a smaller tire, such as either a 44mm or a 1.8"ish tire. Clearance to the side of the tires will also be very tight, unless you don't mind fairly flexy chainstays, but chainstay clearance or stiffness wasn't a criteria.

    And if you do go this route, make sure to tell the builder you want to be able to fully insert a 410 mm seatpost into the seat tube, if that's the case.
    May the air be filled with tires!

  3. #3
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    I always suspected that framebuilders who say 16.5" is a limit are BSing me.
    I think it's a question of economics: you can build a lot of standard frames in a certain time frame. But if somebody demands something special, you need to re-align the jig, buy different tubes, make drawings, think... None of that is pleasant.
    15.5" would be absolutely amazing. I would miss having two front chainrings, though. I also wonder about the seat tube- the farther forward you shift it to clear the rear tire, the closer to horizontal it gets. This means you need a fatter seat tube, which risks impinging on the tire again.
    Because the seat tube would have to be shifted forward, each inch you move the seatpost up or down would mean a bigger horizontal distance. That means you really need to build custom- you have to have all the lengths right for the rider who is going to use the bike.
    _

  4. #4
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    Adjusting the jig is no big deal. It's easier than lowering your seatpost.

    Seat tube aside, there are challenges with chainstays if you want to add the criteria of "relatively stiff." Again, not impossible.

    All in all, I think most builders wouldn't want to go much shorter with their CS because there isn't much demand.
    Last edited by Blaster1200; 04-18-2011 at 03:15 PM.
    May the air be filled with tires!

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    Quote Originally Posted by uphiller
    15.5" would be absolutely amazing. I would miss having two front chainrings, though.
    Can't really do it. You could barely do that on a road bike and it wouldn't work most of the time there. (interference issues)

    I think what most builders are telling you is that the sacrifices you have to make (all of which have been mentioned) outweigh just getting a short stay. You may be able to use a 26'' tire and a 700 front to do it.

    I believe that chainstay length should be varied based on the size, height and style of the rider so ultra short is almost never really the preferred length.

  6. #6
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    What interference issues do you mean? I can think of the following:
    1) Front tire bumps the chainstays- use a machine yoke; use a wider bb shell and matching rear hub
    2) Front tire bumps the seat tube- use a forward-shifted seat tube.
    3) Front tire bumps the front derailleur- ditch the front derailleur; use a wider bb shell and matching rear hub
    I don't know, quantitatively, how much those problems can all be solved, but I do know that there are trials bikes with giant rear tires and 15" or less stays. For that reason, I think 16" is possible, especially with an internally geared rear hub.
    The reason such short stays are desirable is that they make the front end easy to lift. The same can be accomplished with other means- a slack head angle by default puts the rider's weight behind the front axle, making the front end easy to lift.
    Just think of it- the jumpability of a 26" wheeled bike, plus the rollability of a 29" wheeled one. It's something worth a pound or more of extra frame weight, in my view.
    _

  7. #7
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    Quote Originally Posted by uphiller
    For that reason, I think 16" is possible, especially with an internally geared rear hub.
    You may have just added a big problem to the mix. I don't know of any IGH that is wider than 135 mm. Also, I'm pretty sure the Alfine uses a very narrow chainline, which means your front chainring is very close to the tire even with a 73 mm shell, leaving very little room for chainstays - especially short ones. And since you keep mentioning trials riding, have you tried an IGH for trials?

    Quote Originally Posted by uphiller
    The reason such short stays are desirable is that they make the front end easy to lift. The same can be accomplished with other means- a slack head angle by default puts the rider's weight behind the front axle, making the front end easy to lift.
    Just think of it- the jumpability of a 26" wheeled bike, plus the rollability of a 29" wheeled one. It's something worth a pound or more of extra frame weight, in my view.
    I'm not really sure what your objective is by going really short. Lofting the front? Raising the bottom bracket will do that as well...with other consequences.

    I'll tell ya what...For the longest time, I hated 29ers. All the normal production bikes were extremely boring to ride. They felt dead. Couldn't manual, couldn't bunnyhop, and couldn't whip in the air. Just some of my background, I race DH, 4X, and BMX. I ride XC like I'm riding any one of those bikes. I built my 29er SS with 16-5/8" stays, and I've been surprisingly quite happy with it. My opinions of 29ers changed. I go back and forth between this bike my Black Market Mob (with the wheel slammed forward) and my 20" and 24" BMX race bikes (the dropouts on the Intense Podium 24 are filed to allow the wheel to be even further slammed forward). As odd as it sounds, I can get the front end of that 29er up easier than the other bikes. Most of this may also be due to the taller front end. I'm just saying this as you may be chasing something that you may not need or want. Try a 29er with around 16.5" CS that is set up for you and you may be surprised.

    Although I haven't taken my 29er to the BMX track, I do take my Mob there often. And when manualing and tucking over larger whoops and tables, my butt often hits the back wheel. I'm sure it would be way worse with a 29er! So bad that I think that when my butt hits, it would buck me forward. Some day, though, I will regear it and try it.
    May the air be filled with tires!

  8. #8
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    I wasn't thinking of trials riding, although I did do it in the past- had to stop because of back issues and a lack of time. It is a discipline that really requires a ton of time to maintain one's skill level. I don't want to do trials on this bike, I just want to have that front-end lofting ability which is so useful when riding steep stuff or even doing minor drops.
    There are other ways of making the front end easier to lift- slacker head angle (already talked about it), higher bb (less stable, higher center of gravity on a bike that already has big wheels), and making the rear wheel smaller (which is what I don't want to do- I specifically want a 29er).
    I didn't know about the Alfine's narrow chainline... I heard there is a 145mm threaded rear axle for the Rohloff, although I don't know what kind of chainline it has.
    An 83mm bb shell might solve the problem.
    As a non-framebuilder, all of this is pretty theoretical- someone needs to make drawings.
    _

  9. #9
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    Quote Originally Posted by uphiller
    As a non-framebuilder, all of this is pretty theoretical- someone needs to make drawings.
    YOU need to make drawings. that will help to cement it. I already know it won't work without going through contortions and frustrations. The good news is that this is a framebuilders forum, meaning that you should try and build it. You have already realized no pro is going to touch this one meaning if you think it can be done than the only one to do it is you. Grab a torch, the rest of your savings and prove us wrong as you manual all over the mountain.

  10. #10
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    With a BB shell cut-away, you should be able to get below 15.4, easy.

  11. #11
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    Quote Originally Posted by dbohemian
    YOU need to make drawings. that will help to cement it. I already know it won't work without going through contortions and frustrations. The good news is that this is a framebuilders forum, meaning that you should try and build it. You have already realized no pro is going to touch this one meaning if you think it can be done than the only one to do it is you. Grab a torch, the rest of your savings and prove us wrong as you manual all over the mountain.
    That is such a good suggestion.

    At the time I wanted a short chainstay 29er, there were no production ones available, and at the time I didn't know any custom builders who were doing them, so I picked up a torch and started. It's just a bicycle; it's not brain surgery.
    May the air be filled with tires!

  12. #12
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    If you really want to get crazy, throw a 100mm shell or elevated chain stays into the mix to increase your options for silly short.

    If you want flickable and stable, copy the geometry of your favorite 26" bike relative to the axles. Then draw in a 1.5" lower top tube(for standover), and whatever manipulations are necessary for the larger wheel/tire radius. For a bike that get's ridden in a somewhat xc like manner(AM, Trail, Trials/Trails), I don't think you would need to go any lower than 16.25" or so, which D.F.L and I think others(?) have done on a custom basis in the past.

  13. #13
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    If you're of stature that requires sub-16.25-16.5, then go to 650b on the back. That'll bring it way down.

  14. #14
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    Quote Originally Posted by dbohemian
    Can't really do it. You could barely do that on a road bike and it wouldn't work most of the time there. (interference issues)

    I think what most builders are telling you is that the sacrifices you have to make (all of which have been mentioned) outweigh just getting a short stay. You may be able to use a 26'' tire and a 700 front to do it.

    I believe that chainstay length should be varied based on the size, height and style of the rider so ultra short is almost never really the preferred length.
    I'm with Bohm if it's doable build it and bring it here and post it up with pics....lots of pics!!

  15. #15
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    Not sure why we take posts like the OP seriously, seems like a weakness. You could at least make a sketch before insisting something can be done that experienced builders say can't be done. Of course, one meaning for "can't be done," is "you can't build it and I'm not going to."

    I'm not an expert on mtb geometry by any means, but it's a real chore to get the cranks, chainstays and tires to line up in such a way that they aren't intersecting each other. And that's just on paper. Actually fabricating something is another chore.

    there used to be a real fetish for short chainstays on road bikes, but that's pretty much gone away other than people making one-off bikes for show. Turned out that it wasn't that great of an idea.

    Builders have many good reasons for not building something like this. It's a tough business and nobody in it is raking in the bucks. So turning down the opportunity for wasting time on something they wouldn't want to build twice is a no-brainer.

  16. #16
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    I didn't say it was possible. I asked.
    I pushed and insisted, because everybody knows that's the way to see if things are possible. Having pushed and insisted, I see that what I am up against really is impossible- although one builder specifically said that 16.2" is doable, without mentioning anything like wide bb shells or bent seat tubes.
    You guys are framebuilders- I am not. I came here for answers. I got them- what I want seems to be impossible.
    This forum is a place to share information among people in the know- but I also thought I would take advantage of its secondary service, to give information. Sorry for ruffling any feathers.
    _

  17. #17
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    I have a 29er with 16" stays. It's not a big deal as long as you don't want to run both multi-chainrings or big tires with conventional BB widths. You can do one or the other, but not both with the current state of affairs with front derailleurs. You could always run a 83mm BB & 150 rear spacing or a Hammerschmidt or an internal rear hub. Effective chainstay length shorter than 16 on a gearie don't really have much going for them unless you're vertically challenged + the chainline will suck and shifting gets ghosty too. If you're average size, stays longer than 17" effective pretty much suck balls on trail bikes too. Note that I say "effective chainstay length." Stays will always measure longer (by industry definition of the measurement) on a 29er than they will on a 26" even though the rear axle is the same horizontal distance away from the BB center.

    I guess what I'm saying is that getting hung up on arbitrary numbers is a pretty silly way to design or build a bike frame.
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  18. #18
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    DWF- Thanks for the info. Who built this frame for you? Can you post pics?
    _

  19. #19
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    This is what 15" looks like with a 26" wheel and 2.3" tire.

    Short-stay 29ers- the limit?-1111111.jpg
    NOTHING WORKS LIKE CLOCKWORK

    www.clockworkbikes.com

  20. #20
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    Quote Originally Posted by Clockwork Bikes
    This is what 15" looks like with a 26" wheel and 2.3" tire.

    Click image for larger version. 

Name:	1111111.jpg 
Views:	7451 
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    MEH....That's nothing.

    Candida. Tire can touch the BB is wanted, run it 1mm from the BB, whatever.
    This is how to make the CS length as short as the tire will permit, just do it with a 9er.
    Sometimes having a computer with 1,000+ random bike pics is useful(if i can find them).

    Also, note that a Euro BB gives the shortest possible length, since the distance to the center of BB can be closer.
    Attached Thumbnails Attached Thumbnails Short-stay 29ers- the limit?-candida4jz4.jpg  


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  22. #22
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    Quote Originally Posted by DWF
    ........(effective chainstay length) Stays will always measure longer (by industry definition of the measurement) on a 29er than they will on a 26" even though the rear axle is the same horizontal distance away from the BB center.
    .........


    "Always" on a 29er?? Isn't that a matter of bb drop, not wheel size? A 29er could easily be built with the bb in line with the axles, or with a similar bb drop to a typical 26" wheeled bike.

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    Why? Why do you want super short chain stays? Just get a Unicycle! That is about as short a chain stay as you can get!

  24. #24
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    Quote Originally Posted by uphiller
    DWF- Thanks for the info. Who built this frame for you? Can you post pics?
    LOL!
    Beechwold Cycle Works
    Columbus, OH
    http://beechwoldcycleworks.blogspot.com

  25. #25
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    Short stays are fun

    I have a 1x setup (no front derailleur) with a conventional 50mm chainline, clearance for a 2.3 or so, and 41.5cm (effective) chainstays. Loads of fun. If you went outboard on the chainline some, you could take another centimeter off without much trouble. Obviously if you threw everything out the window in terms of parts compatibility, you could go down to about 15.25" before the tire ran into the BB shell.

    42.5-43cm seems to be the practical limit for conventional chainline/front derailleur setups.

    Quick writeup on the bike: http://waltworks.blogspot.com/2011/0...with-less.html

    -Walt

  26. #26
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    Quote Originally Posted by sean salach
    "Always" on a 29er?? Isn't that a matter of bb drop, not wheel size? A 29er could easily be built with the bb in line with the axles, or with a similar bb drop to a typical 26" wheeled bike.
    I'll try to remember you're a literalist in the future.
    Yes, you could go with a super high BB on your 29er. You can also put 24" spinners on your Camry.
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  27. #27
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    Quote Originally Posted by uphiller
    DWF- Thanks for the info. Who built this frame for you? Can you post pics?
    That particular frame was built by a true craftsman, Don McClung.

    <a href="https://www.flickr.com/photos/anvilbikes/4562505996/" title="mcclung_3 by Anvil Bikes, on Flickr"><img src="https://farm4.static.flickr.com/3088/4562505996_1c892a548b.jpg" width="500" height="375" alt="mcclung_3"></a>
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  28. #28
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    Quote Originally Posted by Walt
    Walt, glad to see you're coming around to the short CS and slack head angle. You were one of my candidates to build me a custom frame a while back, but at that time you seemed to be against that.

    Right now, my 29er has a 68.5 degree head angle with the fork set at 95 mm, and it's 67.5 at 120 mm. When I was first building it, I was a bit concerned that it would be too slack. I mostly ride the bike with the fork at 95, since at 120, the front end is a bit too high with the bars I currently have on it, and so it feels a bit awkward. I think the next 29er I build will have 67.5 or 68 degree head angle with the 95 mm fork.

    What BB height/drop is your bike?

    And your right, these kinds of bikes are a blast to ride!
    May the air be filled with tires!

  29. #29
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    Quote Originally Posted by Walt
    I have a 1x setup (no front derailleur) with a conventional 50mm chainline, clearance for a 2.3 or so, and 41.5cm (effective) chainstays. Loads of fun. If you went outboard on the chainline some, you could take another centimeter off without much trouble. Obviously if you threw everything out the window in terms of parts compatibility, you could go down to about 15.25" before the tire ran into the BB shell.

    42.5-43cm seems to be the practical limit for conventional chainline/front derailleur setups.

    Quick writeup on the bike: http://waltworks.blogspot.com/2011/0...with-less.html

    -Walt
    Good article. I agree with your 425'ish but it's got to be a fairly narrow tire if you don't want it to rub on the front d cage. If you want to ride a slack rigid 29er, you're welcome to try my Nancy!
    A man must have enemies and places he is not welcome. In the end we are not only defined by our friends but those against us.

  30. #30
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    I am not really that opinionated.

    I'm against short stays for people who don't need them, I'm against long chainstays for people who don't need them.

    I am generally not one of those "this is the geometry you should ride because it's what _I_ like" people. That said, I think for probably half my customers, shortish (meaning 44cm or less) is good on 29ers. But it's really all over the map. I've done 490mm stays, I've done 415mm ones. Just depends on what you're trying to do.

    BB height on my current bike is 12.25".

    -Walt

    Quote Originally Posted by Blaster1200
    Walt, glad to see you're coming around to the short CS and slack head angle. You were one of my candidates to build me a custom frame a while back, but at that time you seemed to be against that.

    Right now, my 29er has a 68.5 degree head angle with the fork set at 95 mm, and it's 67.5 at 120 mm. When I was first building it, I was a bit concerned that it would be too slack. I mostly ride the bike with the fork at 95, since at 120, the front end is a bit too high with the bars I currently have on it, and so it feels a bit awkward. I think the next 29er I build will have 67.5 or 68 degree head angle with the 95 mm fork.

    What BB height/drop is your bike?

    And your right, these kinds of bikes are a blast to ride!

  31. #31
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    Another builder just told me that he just finished a 16" chainstay 29er. This bike exists; he says that with an 83mm bb shell and no front derailleur, 15.5" can be achieved.
    We also have a photo of a real, existing bike (albeit singlespeed) with 16" stays.
    Difficult? Yes. Unprofitable? Probably- but that's why people pay extra for custom frames.
    Why do it? Because it makes a bike with an easy to lift front end, without sacrificing maneuverability.
    _

  32. #32
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    Quote Originally Posted by uphiller
    but that's why people pay extra for custom frames.
    Question. Are you willing to pay for it? There are builders who do this. One of my faves. Fred at Wolfhound bikes. Get ready to pay a lot and realize you are getting a great value for the dough.



    Man that is a good looking machine!

  33. #33
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    Yes, I saw the Wolfhound- I agree it is pricey, but that's what it costs to get a bike like this. In fact, Fred told me that he can get the stays down to 15.5" with acceptable clearance, provided I go with an IGH.
    As we all noted, it is not easy to build bikes like this.
    _

  34. #34
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    So what about a frame built similar to an old Haro Extreme, with elevated chainstays? Throw in a curved seattube, like a Surly Karate Monkey, and some sliding dropouts, to compensate for varying tire diameters, and call it done?
    I ..... need ..... DIRT!!!!!

    ... and cookies. :D

  35. #35
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    I'm making my own 29er at the moment - horizontal dropout for singlespeed / hub gear with adjustment from 16.5" to 15.9". I could have gone shorter. Regular hub and regular 68mm bb shell.

    It is very easy if you use elevated chainstays, and junking front / rear mechs means you can run the stays very low.

    Pictures are at the two enclosed links - not sure if I can direct link to them (at work so not got time to mess). Feel free to flame my newbie brazing. With a curved seat tube and chainstays bent in 3 planes I've hardly made it easy for myself :-)

    Promise to do a proper post and pics when finished in a few weeks.

    http://loslobos06.blogspot.com/2011/04/garagista-2.html

    http://loslobos06.blogspot.com/2011/04/garagista.html

  36. #36
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    I think I'd sacrifice the elevated stays...

    First off, very nice work!

    Second, I'll be interested to hear how you think the elevated stays ride. I have never ridden such a setup, but I'm told they flex all over the place.

    As Don shows, 16" even is doable without the elevated stays - so IMO the extra few mm you can get with other gimmicks probably isn't worthwhile. I mean, once you can easily loft the front wheel when you want to, what is there to gain?

    -Walt

    Quote Originally Posted by mickuk
    I'm making my own 29er at the moment - horizontal dropout for singlespeed / hub gear with adjustment from 16.5" to 15.9". I could have gone shorter. Regular hub and regular 68mm bb shell.

    It is very easy if you use elevated chainstays, and junking front / rear mechs means you can run the stays very low.

    Pictures are at the two enclosed links - not sure if I can direct link to them (at work so not got time to mess). Feel free to flame my newbie brazing. With a curved seat tube and chainstays bent in 3 planes I've hardly made it easy for myself :-)

    Promise to do a proper post and pics when finished in a few weeks.

    http://loslobos06.blogspot.com/2011/04/garagista-2.html

    http://loslobos06.blogspot.com/2011/04/garagista.html

  37. #37
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    Quote Originally Posted by Walt
    I'm against short stays for people who don't need them, I'm against long chainstays for people who don't need them....Just depends on what you're trying to do.
    Crazy-talk!

    No longer member of the bike industry nor society, so don't hassle me.

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    Thanks for the compliment Walt - means a lot coming from you. I'd been feeling bad that I'd not posted anything having sucked up pages of useful information from this forum.

    I'm loving the underslung bb (worlds lowest e-stays?) shown earlier.

    I hate the idea of using oddball bbs, hubs, massive Q factor, squishing chainstays stupidly flat - hence the e-stay route. I don't like the 29ers I've tried with huge stays that then over compensate with steep head angles to shorten the wheelbase - I'd rather shorten the back end (to climb well when standing up on ss) and get good super steep techy descending with front axle pushed well forwards (70 head, 55mm rake).

    Interestingly, a lot of reviews I dug out from my old 1990 mtb mags actually stated that some e-stay designs felt stiffer (possibly due to smaller triangles, trussed member right across above the bb when viewed from above, more metal along the torsional axis of the frame).

    If it rides OK then I might do a proper comparable bending / torsion test with a regular frame (I work in a structural test lab with some giant mecano). If it flexes like a pig then I'll admit it sucks and cut off the back end to try something else :-)

    I'm using a sort of forward slotted / vertical exit dropout of my own design. If I'd used a regular rear entry one then the tyre could have been brushing the bb shell.

  39. #39
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    The guy who mentioned bb drop is right on. Start cranking the st way forward and how does that affect front/center, weight bias, pedaling dynamics, etc? There are work arounds to a point.

    Get a nice ratio of bb height to axle height (ie not too low) and the bike gets fun. Easier onto the rear wheel, more 'flickable'. The wheels are freekin wagon wheels, no need to sit way down low in between them unless you are a skill-less rider who thinks steep trails, rocks, and roots are a bad thing. "I'm going to for for a roll'.

    Of course standover , etc needs to be kept in mind, but I think that's over rated. I'd rather have the ride optimized, and if there's decent standover, that's gravy. Seems like a holdover from atb fitting in the 80's.

    -Schmitty-

  40. #40
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    I think you misunderstood

    Nobody is talking about moving the rider/saddle forward. If you offset or bend the seat tube to get it out of the way of the tire, as with these short-chainstay 29ers, you also change the angle of the seat tube so that the saddle/rider stay where you want them. So the offset/curved/whatever seat tubes have no effect on the center of gravity or position of the rider.

    Low BBs are good (as low as you can go) until you hit your pedals on things. I don't think there is any controversy about that, wagon wheels or no, as long as we're talking about mountain biking and not trials or BMX or something along those lines.

    -Walt

    Quote Originally Posted by Schmitty
    The guy who mentioned bb drop is right on. Start cranking the st way forward and how does that affect front/center, weight bias, pedaling dynamics, etc? There are work arounds to a point.

    Get a nice ratio of bb height to axle height (ie not too low) and the bike gets fun. Easier onto the rear wheel, more 'flickable'. The wheels are freekin wagon wheels, no need to sit way down low in between them unless you are a skill-less rider who thinks steep trails, rocks, and roots are a bad thing. "I'm going to for for a roll'.

    Of course standover , etc needs to be kept in mind, but I think that's over rated. I'd rather have the ride optimized, and if there's decent standover, that's gravy. Seems like a holdover from atb fitting in the 80's.

    -Schmitty-

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    Yup - Walt is right - my seat tube begins vertical out of the bb, curves around the tyre and then points backwards at 66 degrees. This puts saddle in same place relative to bb and bars and wheels* as my regular 26er (an effective regular "seat tube" angle of about 72 degrees but there would be a tyre in the way).

    *depends if you consider "same" to be front wheel centre or front tyre contact patch

  42. #42
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    wouldnt the elevated chainstay work against the reason for wanting a short chainstay? If they are known for being a flexible ride is it really worth it?
    count your blessings

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    Pressfit BB will also give you some more room to play with.


  44. #44
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    No.

    The constraints we are dealing with in this case all involve tire/chainstay/chainring/seat tube/front derailleur. A wider BB shell may make attaching the stays a bit easier (or allow less bend to achieve the stay positioning desired), but it does not make any difference as to the overall chainstay length.

    This is a common misconception, though. I hear it all the time, but if you stop to think about what parts can interfere with what other parts, the BB shell isn't actually important unless it changes the chainline in some way.

    -Walt

    Quote Originally Posted by shirk
    Pressfit BB will also give you some more room to play with.

  45. #45
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    I understand

    Quote Originally Posted by Walt
    Nobody is talking about moving the rider/saddle forward. If you offset or bend the seat tube to get it out of the way of the tire, as with these short-chainstay 29ers, you also change the angle of the seat tube so that the saddle/rider stay where you want them. So the offset/curved/whatever seat tubes have no effect on the center of gravity or position of the rider.

    Low BBs are good (as low as you can go) until you hit your pedals on things. I don't think there is any controversy about that, wagon wheels or no, as long as we're talking about mountain biking and not trials or BMX or something along those lines.

    -Walt
    Sure, got that. Some guys in their gyrations for short stays carve out the back of the (straight) st, etc. My point was focusing so much on the cs length is myopic. I don't think the lowest possible bb height is best across the board unless your talking touring.

    -Schmitty-

  46. #46
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    Try a scooter sometime

    If the company still exists, and you happen to be at a resort that rents them, check out a "Diggler" (awesome name) offroad scooter. You will figure out very quickly why low is good for cornering and general mayhem - they run something like 6" deck heights and it's *awesome* how well you can lean them over and control traction in turns, even with little 20/24" wheels and minimal suspension. And it's nigh-impossible to endo the things because of the low COG.

    This is the reason fast DH riders and good bike handlers ride through corners (when they're not pedaling, obviously) with their outside pedal/crank down and inside up, too - your COG is lower in this position than it is with the cranks level. The lower you are, the easier it is to lean way into a turn, and yet recover to straighten things out when the turn is over.

    Seriously, you only want the BB high enough that no drivetrain parts will encounter the ground/rocks/roots.

    Your point about CS length in isolation is well taken. Of course it is not the end of the story.

    -Walt

    Quote Originally Posted by Schmitty
    Sure, got that. Some guys in their gyrations for short stays carve out the back of the (straight) st, etc. My point was focusing so much on the cs length is myopic. I don't think the lowest possible bb height is best across the board unless your talking touring.

    -Schmitty-
    Last edited by Walt; 04-20-2011 at 12:57 PM.

  47. #47
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    Walt, I agree with low BBs. However, I'm surprised that you have your BB height at 12.25" with a 100 mm fork. Try around 11-3/4" and I think you'll like it even better.

    I do understand that low BBs aren't for everyone. It does require a skill that many newer riders don't have yet (and many experienced riders don't, either), and that's being able to anticipate a pedal strike 5 feet before it may happen by knowing where in the stroke your crank/pedal will be by the time you get there. Being able to do this, you can slightly stall your pedal stroke(s) shortly before. This is also where high-engagement hubs really help this kind of technical riding.
    May the air be filled with tires!

  48. #48
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    I tried that...

    But it does not work out well for short track racing, which is one of the things I (theoretically) will use this bike for. For all around XC I would go lower, but the specific races I do here require some very hard leaning while pedaling in turns, and I've disovered the hard way that <12" doesn't work well for me.

    -Walt

    Quote Originally Posted by Blaster1200
    Walt, I agree with low BBs. However, I'm surprised that you have your BB height at 12.25" with a 100 mm fork. Try around 11-3/4" and I think you'll like it even better.

    I do understand that low BBs aren't for everyone. It does require a skill that many newer riders don't have yet (and many experienced riders don't, either), and that's being able to anticipate a pedal strike 5 feet before it may happen by knowing where in the stroke your crank/pedal will be by the time you get there. Being able to do this, you can slightly stall your pedal stroke(s) shortly before. This is also where high-engagement hubs really help this kind of technical riding.

  49. #49
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    Ah yes...understand. Seated pedaling while turning can definately cause pedal strike problems. Although I don't race XC/short track, when I'm sprinting around turns, I'm usually standing, in which case I'm rocking the bike to the outside when the inside pedal is down (think BMX/4X/DS/DH, but without berms).
    May the air be filled with tires!

  50. #50
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    Quote Originally Posted by Walt
    Seriously, you only want the BB high enough that no drivetrain parts will encounter the ground/rocks/roots.

    -Walt
    for me that is 12.5-13" on a hard tail and 36T rings w/bash. Still bash pedals and scrape the ring. I do ratchet pedal. Lower than ~12.25" and the handling response seems dead. End up coasting a lot on FS bikes.
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  51. #51
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    Quote Originally Posted by Blaster1200
    Walt, I agree with low BBs. However, I'm surprised that you have your BB height at 12.25" with a 100 mm fork. Try around 11-3/4" and I think you'll like it even better.

    I do understand that low BBs aren't for everyone. It does require a skill that many newer riders don't have yet (and many experienced riders don't, either), and that's being able to anticipate a pedal strike 5 feet before it may happen by knowing where in the stroke your crank/pedal will be by the time you get there. Being able to do this, you can slightly stall your pedal stroke(s) shortly before. This is also where high-engagement hubs really help this kind of technical riding.
    On my trails I can hit pedals with them level. Have a few sidehill trails with a narrow tread. A too low BB means high side hits with normal pedaling. Try to ratchet and you walk up the hill. I avoid climbing it on low BB frames (<=12.2").
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  52. #52
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    Regarding pressfit bb's, wide shells etc...

    The big problem with short stays is trying to fit a tyre, mud, chainstay and chainring(s) into the same space. Hence why people use flat plates in the chainstays etc. A wider shell does not solve the 4 things in one place problem. People use wider shells to allow a bit less bending of the stays and longer bb axles to move the chainrings out of the way a bit then maybe a wider hub to try and correct the chainline (or could build an offset wheel / back end I suppose). The wider bb can also increase things like pedal Q-factor depending on what cranks you are using.

    E-stays let me keep absolutely everything standard and run whatever cranks / rings / hub I please. The gap between the round and unsquished stays at the tyre is 80mm which means 10mm mud room each side with most tyres.

    Nobody here really knows if there is a flex problem or not. E-stays were in production 20 years ago so only a few of us were riding back then (and I never owned one but read plenty). But today there are lots of suspension designs that mimic the "problems" of E-stay flex yet nobody comments on it.

    So I'm building one to try. And I've thought up a realistic way to load the bike in the lab and measure flex so will be able to report back objectively in a month or two. Just need to convince a friend to lend me his regular 29er for comparative measurments....

  53. #53
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    Quote Originally Posted by mickuk
    Nobody here really knows if there is a flex problem or not. E-stays were in production 20 years ago so only a few of us were riding back then (and I never owned one but read plenty). But today there are lots of suspension designs that mimic the "problems" of E-stay flex yet nobody comments on it.
    There are actually no suspension bikes that 'mimic' elevated chainstays. Firstly, the stays are dynamic and damped, while 'regular' elevated chainstay bikes aren't.

    The reason you don't see elevated chainstay bikes today, is because they're all broken.. The chainstays go from being in compression with the chain forces, to being in bending, and that bending load finds a nice little stress point somewhere in the design and *pop-o* goes the chainstay.

    You just don't need chainstays that short. I had a Mantis with stays under 16" "back in the day", and it was horrid. It had a novel sensation of being able to 'steer with your bum', but the weight distribution was *****, it handled like *****, steered like *****, climbed like *****.....why bother?

    My 29er with 17.50" chainstays has out climbed every single bike I've ever owned in 25 years of Mountain Biking. I'd probably like to go to 17" on the next one, but any shorter than that for anything but a Trials orientated frame or for someone that's 5ft tall, I don't see the point.
    No longer member of the bike industry nor society, so don't hassle me.

  54. #54
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    I owned a Fisher Montare elevated chainstay bike back in 1988 or 89. It was a lot of fun here on New England trails but every single one I knew of (which amounted to 6 or 7 bikes) broke the seat tube right below the chainstays. There is a lot of force on the BB, and the elevated CS leave the bottom of the seat tube cantilevered out there in space. Never did hear of one breaking the CS, but that might only because the ST broke first.

    I also rode a Nishiki Alien for a while. There wasn't noticable flex in the rear end of either of these bikes, but I may not be the most sensitive guy around.

    B

  55. #55
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    Wow Thylacine - I never knew you could take just one frame dimension and blame it for all aspects of a bike's handling!

    If you join the chainstays half way up the seat tube then yes, there is a big bending moment due to both rider weight and chain tension. If you join them very low down (just above the chainring) then the bending moment due to chain tension becomes much smaller. You also go back to a fairly conventional sized rear triange that is better able to handle the vertical loading. My stays are mounted fairly low down but not absolutely as low as possible until I understand how much clearance is needed to avoid chain slap.

    The Fisher design was notorious for failures - as you say, it put a big bending moment into the middle of an unbraced seat tube. Hardly a surprise.

    I know plenty of Alpinestars steel frames that are still going strong in regular use and surprisingly saw a Brave E-stay in the local bike shop just last week. So they haven't ALL broken.

    Anyone know how things like Yeti Ultimates and Funks survived?

  56. #56
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    Anecdotal evidence: I know one guy who has been riding a Yeti Ultimate continuously since 1992 or so. It doesn't get more anecdotal than that- plus it is a heavy bike.
    _

  57. #57
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    The Yetis mostly broke.

    ...but they all broke at the dropouts, so it's hard to say if they would have broken elsewhere.

    You know, I would have said about the same thing as Thy as of 5 years ago. But I spent some time messing with short bikes for customers, rode some, and I ended up finally building one for myself - and like it. Slack and short is a lot of fun.

    Then again, I've ridden so many bikes at this point in my life that anything new and different feels cool for a while. Maybe I'll be on 18" chainstays and raving about them in a year. Regardless, what the OP wants is not totally unreasonable, IMO.

    -Walt

    Quote Originally Posted by mickuk
    Wow Thylacine - I never knew you could take just one frame dimension and blame it for all aspects of a bike's handling!

    If you join the chainstays half way up the seat tube then yes, there is a big bending moment due to both rider weight and chain tension. If you join them very low down (just above the chainring) then the bending moment due to chain tension becomes much smaller. You also go back to a fairly conventional sized rear triange that is better able to handle the vertical loading. My stays are mounted fairly low down but not absolutely as low as possible until I understand how much clearance is needed to avoid chain slap.

    The Fisher design was notorious for failures - as you say, it put a big bending moment into the middle of an unbraced seat tube. Hardly a surprise.

    I know plenty of Alpinestars steel frames that are still going strong in regular use and surprisingly saw a Brave E-stay in the local bike shop just last week. So they haven't ALL broken.

    Anyone know how things like Yeti Ultimates and Funks survived?

  58. #58
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    Quote Originally Posted by mickuk
    Wow Thylacine - I never knew you could take just one frame dimension and blame it for all aspects of a bike's handling!
    Well, I've also had bikes where the front end geometry was similar enough so clearly that wasn't the problem.

    Quote Originally Posted by mickuk
    The Fisher design was notorious for failures - as you say, it put a big bending moment into the middle of an unbraced seat tube. Hardly a surprise.

    I know plenty of Alpinestars steel frames that are still going strong in regular use and surprisingly saw a Brave E-stay in the local bike shop just last week. So they haven't ALL broken.

    Anyone know how things like Yeti Ultimates and Funks survived?
    Any e-stay bikes that have survived are either complete pigs or have been babied and are now only brought out at gatherings of the Retro forum.

    It's kinda like saying some extinct species had it right all along.

    No longer member of the bike industry nor society, so don't hassle me.

  59. #59
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    I have been riding a 26" wheeled bike with 16" stays for awhile now, as an XC, not a trials bike. It exhibits none of the traits you mentioned. How many short-stay bikes have you ridden?
    _

  60. #60
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    How many years as a bike designer would you think would entitle one to an informed opinion?

    Is 20 enough?
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  61. #61
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    Sure, it is. And riding my own bike for 8 years is also enough to know why I like them. Your binary view is a little over the top.
    _

  62. #62
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    My Mantis XCR-EC (and early generation OCLV carpet fibre Gary Fissure) are holding up quite nicely... hanging in the garage.

    The Nem Pro 29er in the background is hanging because the HA is a tad steep for my clapped out old 90mm Maverick SC, and the stays a tad long for my style of riding.
    And of course the Bike Friday isn't what I would consider trail worthy.

    I have yet to try a 29er with sub 17.25" stays, but I have been convinced for a long time that somewhere between 16.5"-16.75" lies the magic number for me. I'd like to be able to finesse the front end around with little or no notice like I can on my Intense 5.5.

    Last edited by MrCookie; 04-25-2011 at 01:29 AM.

  63. #63
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    You would have to post a photo of a Mantis XCR in my size, wouldn't you.

    You don't need a Kidney by any chance, do you?
    No longer member of the bike industry nor society, so don't hassle me.

  64. #64
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    Kidneys are fine, may need a new liver by the time I am out of Engineering school...
    That Mantis is a 23 inch. Not too many of those around... and no, it doesn't fit me :-)

  65. #65
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    Well hey, I'm 6ft 4ins, so don't let that poor thing just hang there gathering dust!
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  66. #66
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    I have just got the first prototype of a 29er I have been working on,
    ti e stay
    actual chain stay length 417
    bb height 300mm

    more details here http://twentynineinches.com/2011/05/...ain-stay-29er/

  67. #67
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    While I'm a big proponent of short stay 29ers and have a soft spot for elevated stays, I can't help but think that elevated stays with that much bb drop(300mm bbheight) is only going to exaggerate the flexiness of the bb.... Looks sweet though.

  68. #68
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    Sean - I measured the bb drop on my steel rolling chassis last night - 114mm centre of bb to underside of chainstay - is that more to your liking? Just need to finish the seatstays and build up some fillets....

  69. #69
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    I would guess that less distance from the chainstay connection point to the bb is going to result in less unwanted flex. The 26" e-stay bikes likely had less than 30mm bb drop, maybe 60mm from the actual e-stays?. If you're going with one ring up front, maybe you could add some sort of gusset or support tube from the chainstays where they cross the plane of the seat tube down to the bb shell.

    I could be overestimating the amount of flex that could come from that design though.

    EDIT: the Mantis pictured above doesn't appear to have much less than 114mm st exposed below the e-stays though....

  70. #70
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    the flex on my bike isnt too bad it's a little more than my Ragley TD-1 but too much i suspect to run a belt drive .. my main reason for the high chainstay design was mud clearance i think i have about 85mm between the chainstays where the tyre is ,

    lowering the chainstays would mean they would be either tighter to the tyre or to the cranks

    I did try to design this to do everything in terms of gears hubs, single speed ,derailier and belt drive,,,, i havnt tried a front a front mech on the bike yet but suspect I will run into problems , 2x10 with a top mount front mech ( i think) may be possible

    my seat stay and chainstay are both 22mm

  71. #71
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    Quote Originally Posted by sean salach
    I would guess that less distance from the chainstay connection point to the bb is going to result in less unwanted flex. The 26" e-stay bikes likely had less than 30mm bb drop, maybe 60mm from the actual e-stays?. If you're going with one ring up front, maybe you could add some sort of gusset or support tube from the chainstays where they cross the plane of the seat tube down to the bb shell.

    I could be overestimating the amount of flex that could come from that design though.

    EDIT: the Mantis pictured above doesn't appear to have much less than 114mm st exposed below the e-stays though....
    The e-stay frames had the CS well more than 60mm above the BB. Most (all?) had the FD (all high clamp) below the stays and 46-50t chainrings were common.
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  72. #72
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    A lot (but not all) of the old school 26" e-stays ran almost a straight line between rear dropout and head tube - this left a similar bb drop as per Ade's bike.

    The reason a lot of 26ers were built like that was to make things easy and use standard parts - it leaves loads of room for front mech and 3 rings and the chain is well below the stay so you don't get any slap. The stays didn't need much or any shaping and they could just use oversize wishbone seatstays as chainstays.

    The lower you make the stay the more you have to think about chain clearance, under stay chainslap and shaping the stay to avoid heels and pedals. If running a single ring you can go lower with the stay. Generally, the lower the stay is at the front / seat tube, the more "drop" is needed to clear the chain and then meet the rear dropout. I'm running the stay horizontal with a small bend down at the back to meet the dropout. This hopefully gives enough clearance to run up to 32:22 singlespeed / hub gear. I'll also try it with a rear cassette and see what the max sprocket is (but think I'll start to get chainslap with a 28t).

    Made and mitred the seatstays last night. Not totally happy with the shape (looks clunky compared to the swoopy chainstays) but I've no spare material so will be using them anyway for first proto - more important I try to ride the thing to add to the discussion. Need some time at work with the gas bottles this weekend.....

  73. #73
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    Is there some special defect you Poms have adopted where you're completely unaware of why elevated chainstays as a concept died 15 years ago?

    You're spending way too much time thinking about whether you 'can', as opposed to weather you 'should'. What are you actually trying to achieve, over and above a meaningless, absolutist theory where you try to get the shortest possible chainstays with 29" wheels 'just because you can'.

    What....are....you....trying.....to......achieve?

    You know, the scientific rigor of having a problem and trying so solve it, rather than the other way around.
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  74. #74
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    Why does it bother you so much that people are trying this? Since when is it a bad thing for people to attempt to find limits of anything? What's the future like?

  75. #75
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    Why do we want short stays? We've been through this- so you can lift the front wheel easier when navigating tight, technical terrain. The same thing can be achieved with some combo of a slack HA, higher bars, or a higher BB, but none of those is suitable on a 29er: the bars are already relatively high, the handling is relatively slow so a slack HA will make it worse, and the center of gravity is also high, so a higher BB won't help.
    Maybe the reason such short stays displease you is because you're 6'4" and they just don't fit your size and riding style?
    What's a Pom?
    Yeah, elevated chainstays seem to have been abandoned for good reason. Why does it drive you up the wall that others will try it?
    Why do you slight other professional framebuilders? Have you ever seen a Teasdale frame in person? I can say he was honest, a pleasure to work with, and built me something no one else would (a 26er with 16" stays and room for a big tire) for a good price, and with pretty good craftsmanship.
    No one here is forcing short stays on you- it's you who's telling others what to do. You're the absolutist.
    _

  76. #76
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    If you want super short chain stays why not go 69'r or 650b in back? Why not run a road tire in the back? Do you ever "loop out" when climbing super steep stuff? Can you unclip fast enough?

  77. #77
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    Quote Originally Posted by sean salach
    Why does it bother you so much that people are trying this? Since when is it a bad thing for people to attempt to find limits of anything? What's the future like?
    What, you mean like who can make the biggest hamburger, or a mock Porsche made from icypole sticks?
    No longer member of the bike industry nor society, so don't hassle me.

  78. #78
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    Wow...

    Lots of hate for the super short stays out there. I agree they are not for everyone, but for me personally, my 16.3" chainstay 29er is the best hardtail I've ever ridden. And I've got a 36" inseam. Loop out? Nah, just roll those wrists and slide forward.

    Great traction, great ability to get around turns, fun to jump up and down things on... I love it. Some folks don't like that style of riding, or need a bike that they can relax on and ride out fast/rough stuff when they're tired - and super short isn't good for those folks.

    It's worth pointing out that I come from the longer-is-better camp, so I don't have a pre-existing bias here. I expected to dislike my new setup (and built it with sliding dropouts to allow me to add 20mm back to the chainstays) but I was wrong, at least in this case.

    -Walt
    Last edited by Walt; 05-13-2011 at 03:46 PM.

  79. #79
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    Maybe someday we'll have telescoping chainstays similar to telescoping seatposts, and with a single lever you will be able to drop the saddle and tuck the rear wheel in. Maybe when we can have our cake and eat it too will the arguments finally end

  80. #80
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    Why is it impossible to comprehend that just because you're not an advocate of seeing how short you can make something just for the sake of it, that I'm somehow against short stays? It was the same ******** when 29" wheels came on board - if you didn't think they were the best things ever, suitable for everyone and for every application, you were a 'hater'.

    I never said I think short chainstays are 'bad'. What I think is bad is not engaging the brain before getting the hacksaw out, and chasing some 'extreme' just because you can.

    Anyway, time for breakfast. Gunna go see how high I can stack Weet-Bix.......
    No longer member of the bike industry nor society, so don't hassle me.

  81. #81
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    He's a troll.
    He is trying to sell bikes which seem to have production or close to production geometry at custom costs.
    It's a weird combination. Wonder what he gets out of it.
    _

  82. #82
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    Quote Originally Posted by uphiller
    Why do we want short stays? We've been through this- so you can lift the front wheel easier when navigating tight, technical terrain....Maybe the reason such short stays displease you is because you're 6'4" and they just don't fit your size and riding style?
    Quote Originally Posted by uphiller
    Yeah, elevated chainstays seem to have been abandoned for good reason. Why does it drive you up the wall that others will try it?
    Did you read that before you pressed the Submit button?

    Quote Originally Posted by uphiller
    Why do you slight other professional framebuilders? No one here is forcing short stays on you- it's you who's telling others what to do. You're the absolutist.
    I'm sorry, but I'm not the one advocating making something as short as physically possible just to find a solution looking for a problem, so I fail to see how that makes me 'absolutist', and since starting Thylacine Cycles, one of the fit and handling backbone philosophies of what I do has been the strong advocation of varying chainstay length for the optimal fit and handling!

    I think if you re-read all of my posts in this thread, you'll find that I'm not "telling others what to do", I haven't "Slighted" any framebuilders, and that I've been advocating the complete opposite of being "absolutist" all along.
    No longer member of the bike industry nor society, so don't hassle me.

  83. #83
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    Quote Originally Posted by uphiller
    He's a troll.
    He is trying to sell bikes which seem to have production or close to production geometry at custom costs.
    It's a weird combination. Wonder what he gets out of it.
    Who is this in reference to?
    No longer member of the bike industry nor society, so don't hassle me.

  84. #84
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    Quote Originally Posted by uphiller
    stuff
    What's a Pom?
    stuff...

    Pom = Redcoat
    thanks Google Alternative names for the British
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

  85. #85
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    I was talking about you, Thylacine.
    Please allow me to take back the bit about your bikes not really being custom. That was low, and apparently not true. Having seen a few pics of your welds, you obviously are a talented builder.
    I do stand by saying that you act like a troll, at least in this post. I haven't read your other ones- I came here from the only other forum I visit with regularity, namely VRC. You might just be a helpful person in general.
    Elevated stays. Short stays. Two absolutely separate things. I don't see any advantage in elevated chainstays, and never suggested them.
    You say short chainstays are a solution looking for a problem, ie, that there is no problem. In fact, apart from my last comment about your craftsmanship, my brain is fully engaged, and I know why I want short stays. There is a problem, though, and that is, I have said it many times, it is hard to bunnyhop a 29er, unless the stays are short, or you change the geometry in other ways that have very negative results. I have never advocated short stays for the sake of short stays. I advocated them for myself, so I could lift the front wheel. I can't even get over a curb on a standard 29er. That's a real problem.
    I never advocated short stays for anyone other than myself.
    I asked how short they can be gotten partly out of curiosity. Exaggerating certain aspects of a design is useful in general for seeing where it leads. I don't advocate them for anyone but myself and the others who want a big-wheeled bike that still can be easily jumped.
    You did slight another framebuilder, Tom Teasdale, by name, when you said he was a 'utility builder'. In fact, Tom builds bikes, including hard to take on projects like the 16" stay 26er with fat tire clearance I mentioned, and even trikes and recumbents, definitely not the stuff anyone builds to make a quick buck. He builds in steel and aluminum. He bends his own tubes. He does some of the machining himself, as when he made a custom reinforced disc mount to withstand the force of pedal kicking. Tom is no more a 'utility builder' than you.
    If I 'hated on' anyone else, it was the people who said 'that can't be done'- and then disappeared when photos started showing up of real 29ers with the chainstay lengths I was talking about.
    So- please accept my apology.
    Can we boil it down to "a few people would derive more enjoyment from the practical benefits of riding with ultra-short stays and a few would derive enjoyment from trying something novel, while most of us would be happy with more conventional dimensions", and then leave it to the people who are interested in the idea to talk about it?
    _

  86. #86
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    Quote Originally Posted by uphiller
    I was talking about you, Thylacine.
    Please allow me to take back the bit about your bikes not really being custom. That was low, and apparently not true. Having seen a few pics of your welds, you obviously are a talented builder.
    I do stand by saying that you act like a troll, at least in this post. I haven't read your other ones- I came here from the only other forum I visit with regularity, namely VRC.
    Well, at least you had the guts to own what you said. My bikes are completely custom made, handmade in the US, and the shortest chainstay'd 29er frame I've done to date is 415mm.

    I think you're confusing 'troll' with 'devil's advocate'. Not ONCE I have I heard any discussion on this thread where the jump-off point is a discussion about who an individual is, where they ride, their physiology, AND THEN an hypothesis on why the absolute shortest chainstays would be the solution to the problem.

    Quote Originally Posted by uphiller
    I asked how short they can be gotten partly out of curiosity. Exaggerating certain aspects of a design is useful in general for seeing where it leads. I don't advocate them for anyone but myself and the others who want a big-wheeled bike that still can be easily jumped.
    Isn't it pretty obvious that the shortest possible stays are the wheel diameter, plus 1/2 the dia of the BB shell +1mm? Where to from here?

    Quote Originally Posted by uphiller
    You did slight another framebuilder, Tom Teasdale, by name, when you said he was a 'utility builder'. Tom is no more a 'utility builder' than you.
    I'm sure he's absolutely beside himself.

    Quote Originally Posted by uphiller
    If I 'hated on' anyone else, it was the people who said 'that can't be done'-......So- please accept my apology.
    Sure.

    Quote Originally Posted by uphiller
    Can we boil it down to "a few people would derive more enjoyment from the practical benefits of riding with ultra-short stays and a few would derive enjoyment from trying something novel, while most of us would be happy with more conventional dimensions", and then leave it to the people who are interested in the idea to talk about it?
    Only if you're comfortable having those ideas put to the challenge.
    No longer member of the bike industry nor society, so don't hassle me.

  87. #87
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    You did put the devil in devil's advocate.
    The comments about your height and riding style- at one point you said that one short stay bike you rode felt like you could steer it with your butt- it seemed that maybe your ideas about how that bike handled could come from being taller than the rest of us. No offense intended- I was searching for the source of your reasoning and figured you were generalizing from your own discovery that that geometry was bad for you personally. A person who's 5'7" and someone who is fully 9" taller are going to have completely different impressions of the same bike. About riding style- I meant style and terrain, not ability. I thought, maybe this guy is in a place where this type of bike is of no benefit- straightaways, bumpy ones, all-day rides. I have no idea of your skill level.
    As for Tom- I am sure he's not worried about it, but hinting that his bikes are something like pre-fab or semi-custom is just not true, whether he is annoyed or not.
    I look forward to riding his next creation: a 29er with 15.75" stays, a 1x9 or Rohloff drivetrain, and a super-low top tube, for my own XC riding preferences. Not that I'm a star rider, or that I "need" a special bike for what I do. In any case, I will miss my XC-Pro thumbshifters.
    Can we see a pic of the 415mm stay 29er?
    _

  88. #88
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    Quote Originally Posted by Thylacine
    Is there some special defect you Poms have adopted where you're completely unaware of why elevated chainstays as a concept died 15 years ago?

    You're spending way too much time thinking about whether you 'can', as opposed to weather you 'should'. What are you actually trying to achieve, over and above a meaningless, absolutist theory where you try to get the shortest possible chainstays with 29" wheels 'just because you can'.

    What....are....you....trying.....to......achieve?

    You know, the scientific rigor of having a problem and trying so solve it, rather than the other way around.

    If you can't see how this post reads as condescending, then there's some sort of language barrier here. Maybe you really were just honestly trying to ask 'why', because you're incapable of grasping that people might have different riding styles than you. Kind of odd for a pro frame builder to not understand that, so I gave you the benefit of the doubt and assumed you were smart, but just being a troll.

    To humor you though. I'm a former trials and street(bmx) rider. I'm used to bikes with very short chainstays and prefer them. They suit my riding style better. I also like 29" wheels. I like the low slung handling of them to a degree, on some trails, but also like to ride much techier trails that allow me to utilize some of the skills I learned as a trials rider. I've got a pile of 29" tires. The wheel size works for me. Having a frame with a trials leaning all mountain geometry, but with a little bit of added rollover from the larger wheels sounds ideal to me. No one is going around spouting any kind of absolutist propaganda about the currently nonexistant super short 29er chainstays being the end all be all. Not sure where you read that, maybe it's that language barrier popping up again.

  89. #89
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    Don Ferris thinks you're spouting something :

    "I'll try to remember you're a literalist in the future. Yes, you could go with a super high BB on your 29er. You can also put 24" spinners on your Camry."
    - DWF

    "No one is going around spouting any kind of absolutist propaganda about the currently nonexistant super short 29er chainstays being the end all be all. Not sure where you read that," - sean salach

    Press the 'page one' button, and read all of Uphillers' posts. THIS ENTIRE THREAD is about "How short can we make them / I heard 15.5" / I think framebuilders who say contrary are full of crap".

    Not ONCE in this entire thread, has the OP or anyone else essentially even bothered to mention where they ride, the type of riding they do, if they race or not, how tall they are, how much they weigh, what their preferred saddle setback is.....and then nominated some issue they have with their current or historical bikes and then asked the questions "How short should / could I make my chainstays, and would this solve the problem?"

    It's all been meaningless chatter with absolutely no context.

    "I like it" does not constitute a context.

    If you'd bothered to read or do any research rather than just go someone you don't agree with, you'll notice that I mentioned I have done frames with stays as short as 415mm with 29" tyres, so your comment "incapable of grasping that people might have different riding styles than you." is complete rubbish.

    I design bikes to suit a task, suit a geography, and suit a physiology. I don't just go "How short is the shortest EVAR! Let's make that!" This is what Uphiller has been advocating for the entire thread - back-read it if you need to. So sue me - I don't subscribe to that high-school methodology (or lack thereof).

    Honestly, I'm quite happy being seen as being condescending because you can only tolerate so much banality before you crack. You get experienced professionals make comments such as -

    "I'm against short stays for people who don't need them, I'm against long chainstays for people who don't need them. " - Walt

    There are numerous others from Don, Myself, Steve and others - guys that have actually built bikes - with context - with chainstays of a myriad different lengths. We haven't had to resort using extinct designs such as elevated chainstays which patently don't work and aren't necessary.

    And yet here we are in this thread, with two or more people building e-bikes.....in 2011.....that (Ade's at least) not only have no design rigor aside from "Let's do it!", but also bring absolutely nothing to the table - they are no different to the ones of 15 years ago, solve none of their problems, don't improve any of the parts where they patently ignore physics, nothing. It's an extension of the 29er dogma I had to sit through for about 5 years, now as if 29" wheels had the supermegawesome power to make elevated chainstays magically work.

    Everything has it's place as I've always, ALWAYS advocated, but you can't just take one figure, one component, and pretend that it has some context when none is provided. In the same breath, you can't claim much design validity when you invent a solution and go looking for a problem - especially when numerous professional bicycle designers have already stated the environment and context in which a solution already exist where it's appropriate.
    No longer member of the bike industry nor society, so don't hassle me.

  90. #90
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    Quote Originally Posted by Thylacine
    Don Ferris thinks you're spouting something :

    "I'll try to remember you're a literalist in the future. Yes, you could go with a super high BB on your 29er. You can also put 24" spinners on your Camry."
    - DWF

    "No one is going around spouting any kind of absolutist propaganda about the currently nonexistant super short 29er chainstays being the end all be all. Not sure where you read that," - sean salach
    Pretty unrelated context on those two. Don mistyped something, using the absolute term "always" when "typically" would have been a lot more accurate.

    Quote Originally Posted by Thylacine
    Press the 'page one' button, and read all of Uphillers' posts. THIS ENTIRE THREAD is about "How short can we make them / I heard 15.5" / I think framebuilders who say contrary are full of crap".
    I went ahead and did that. He said: "I always suspected that framebuilders who say 16.5" is a limit are BSing me." A statement you(415mm) and several others proved to be true throughout the thread.

    Quote Originally Posted by Thylacine
    Not ONCE in this entire thread, has the OP or anyone else essentially even bothered to mention where they ride, the type of riding they do, if they race or not, how tall they are, how much they weigh, what their preferred saddle setback is.....and then nominated some issue they have with their current or historical bikes and then asked the questions "How short should / could I make my chainstays, and would this solve the problem?"

    It's all been meaningless chatter with absolutely no context.

    "I like it" does not constitute a context.

    Quotes from the op. On the first page. Which you directed me to because I apparently have reading comprehension issues.

    "The reason such short stays are desirable is that they make the front end easy to lift. The same can be accomplished with other means- a slack head angle by default puts the rider's weight behind the front axle, making the front end easy to lift.
    Just think of it- the jumpability of a 26" wheeled bike, plus the rollability of a 29" wheeled one."


    "I wasn't thinking of trials riding, although I did do it in the past- had to stop because of back issues and a lack of time. It is a discipline that really requires a ton of time to maintain one's skill level. I don't want to do trials on this bike, I just want to have that front-end lofting ability which is so useful when riding steep stuff or even doing minor drops.
    There are other ways of making the front end easier to lift- slacker head angle (already talked about it), higher bb (less stable, higher center of gravity on a bike that already has big wheels), and making the rear wheel smaller (which is what I don't want to do- I specifically want a 29er)."



    hhmmmmm.....


    Quote Originally Posted by Thylacine
    If you'd bothered to read or do any research rather than just go someone you don't agree with, you'll notice that I mentioned I have done frames with stays as short as 415mm with 29" tyres, so your comment "incapable of grasping that people might have different riding styles than you." is complete rubbish.

    I did notice that. Your trophy is in the mail.


    Quote Originally Posted by Thylacine
    I design bikes to suit a task, suit a geography, and suit a physiology. I don't just go "How short is the shortest EVAR! Let's make that!" This is what Uphiller has been advocating for the entire thread - back-read it if you need to. So sue me - I don't subscribe to that high-school methodology (or lack thereof).

    Honestly, I'm quite happy being seen as being condescending because you can only tolerate so much banality before you crack. You get experienced professionals make comments such as -

    "I'm against short stays for people who don't need them, I'm against long chainstays for people who don't need them. " - Walt

    There are numerous others from Don, Myself, Steve and others - guys that have actually built bikes - with context - with chainstays of a myriad different lengths. We haven't had to resort using extinct designs such as elevated chainstays which patently don't work and aren't necessary.
    Extinct designs? Like 29ers? Not sure which 'side' of the argument you were on by your comment on 29ers in the next paragraph. If you were against them for 5 years, you would think you would have learned something from that, but I doubt you were against them. Which makes it seem kind of odd that you would be against rehashing old technology with new materials that might be better suited to the design.

    Quote Originally Posted by Thylacine
    And yet here we are in this thread, with two or more people building e-bikes.....in 2011.....that (Ade's at least) not only have no design rigor aside from "Let's do it!", but also bring absolutely nothing to the table - they are no different to the ones of 15 years ago, solve none of their problems, don't improve any of the parts where they patently ignore physics, nothing. It's an extension of the 29er dogma I had to sit through for about 5 years, now as if 29" wheels had the supermegawesome power to make elevated chainstays magically work.

    Everything has it's place as I've always, ALWAYS advocated, but you can't just take one figure, one component, and pretend that it has some context when none is provided. In the same breath, you can't claim much design validity when you invent a solution and go looking for a problem - especially when numerous professional bicycle designers have already stated the environment and context in which a solution already exist where it's appropriate.

    The op wasn't just looking at one component of frame design and ignoring all others. He specifically adressed this on the first page, where you directed me to reread his posts, because I apparently have reading comprehension issues....

    I already quoted it above, but I'll quote it again, just in case I'm not the only selective reader here...

    "There are other ways of making the front end easier to lift- slacker head angle (already talked about it), higher bb (less stable, higher center of gravity on a bike that already has big wheels), and making the rear wheel smaller (which is what I don't want to do- I specifically want a 29er)."

    He even went so far as to accept that his desired chainstay length was impossible based on the advice of framebuilders. On the first page even. Then a bunch of other frame builders piped in and hinted that it was possible.

    "I didn't say it was possible. I asked.
    I pushed and insisted, because everybody knows that's the way to see if things are possible. Having pushed and insisted, I see that what I am up against really is impossible- although one builder specifically said that 16.2" is doable, without mentioning anything like wide bb shells or bent seat tubes.
    You guys are framebuilders- I am not. I came here for answers. I got them- what I want seems to be impossible.
    This forum is a place to share information among people in the know- but I also thought I would take advantage of its secondary service, to give information. Sorry for ruffling any feathers."

  91. #91
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    I am an experienced rider, know why I want short chainstays, explained why I want them in post 6 and 8 and then again later, and never advocated them for anyone.
    Tom Teasdale builds great frames. Walt gave me a very instructive talk a few weeks ago about this topic, without me giving him anything in return.
    Walt's position that he's against short stays for people who don't need them for what they do, and against long stays for people who don't need them for what they do is banal, but this is no different from saying you build bikes "to suit a task, suit a geography, and suit a physiology"- it's a different way of stating the same thing: "I am a custom frame builder".
    Last edited by uphiller; 05-15-2011 at 04:11 PM.
    _

  92. #92
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    Quote Originally Posted by sean salach
    I went ahead and did that. He said: "I always suspected that framebuilders who say 16.5" is a limit are BSing me." A statement you(415mm) and several others proved to be true throughout the thread.
    The absolute limit is actually the wheel diameter, plus half the dia of the BB shell, plus 1mm. Nobody is BSing anybody - 415 is what I built based on THE WHOLE PICTURE. Who here has actually bothered to draw anything up, and who has arrived at a chainstay length based on anything but plucking a random "The smaller the number the better" out of the sky?.

    Quote Originally Posted by sean salach
    Quotes from the op. On the first page. Which you directed me to because I apparently have reading comprehension issues.

    "The reason such short stays are desirable is that they make the front end easy to lift. The same can be accomplished with other means- a slack head angle by default puts the rider's weight behind the front axle, making the front end easy to lift.
    Just think of it- the jumpability of a 26" wheeled bike, plus the rollability of a 29" wheeled one."


    "I wasn't thinking of trials riding, although I did do it in the past- had to stop because of back issues and a lack of time. It is a discipline that really requires a ton of time to maintain one's skill level. I don't want to do trials on this bike, I just want to have that front-end lofting ability which is so useful when riding steep stuff or even doing minor drops.
    There are other ways of making the front end easier to lift- slacker head angle (already talked about it), higher bb (less stable, higher center of gravity on a bike that already has big wheels), and making the rear wheel smaller (which is what I don't want to do- I specifically want a 29er)."


    You do have comprehension issues. Your quoting proves my point - no talk of physiology AT ALL. THE MAJORITY of the frame geometry is FIT, and yet, yet no talk of fit at all. From anyone.

    The only useful bit of information Uphiller has provided is that he prefers shorter stays "because it's easier to lift the front wheel". Correct. Aside from the fact that we have no physiological paramters to make any statement regarding how short would be necessary for this, and because of this, the thread denigrates into "How short can we go!" like a high school playground debate, and because there is no design rigor, we're now looking at e-stay bikes being commissioned. Overwhelming evidence they don't work and are unnecessary. And yet, here we are.

    Quote Originally Posted by sean salach
    If you were against them [29ers] for 5 years, you would think you would have learned something from that, but I doubt you were against them. Which makes it seem kind of odd that you would be against rehashing old technology with new materials that might be better suited to the design.
    You're either with us or against us, huh?

    I don't know how old you are, but there really isn't any 'new materials' that would make an e-stay bike work, and certainly none that can defy the laws of physics to the point where you can literally just do the exact same designs that were done 15 years ago and somehow they will magically work. They've been made in carbon (Trimble) Titanium (Merlin) and steel, but YET AGAIN, if you don't have any context over and above 'coz I want it', you're still a solution looking for a problem.

    Maybe 16.75" would be enough for Uphiller? Maybe 16.5? At this juncture, who knows?

    Quote Originally Posted by sean salach
    The op wasn't just looking at one component of frame design and ignoring all others. He specifically adressed this on the first page, where you directed me to reread his posts, because I apparently have reading comprehension issues....

    I already quoted it above, but I'll quote it again, just in case I'm not the only selective reader here...

    "There are other ways of making the front end easier to lift- slacker head angle (already talked about it), higher bb (less stable, higher center of gravity on a bike that already has big wheels), and making the rear wheel smaller (which is what I don't want to do- I specifically want a 29er)."

    He even went so far as to accept that his desired chainstay length was impossible based on the advice of framebuilders. On the first page even. Then a bunch of other frame builders piped in and hinted that it was possible.

    "I didn't say it was possible. I asked. I pushed and insisted, because everybody knows that's the way to see if things are possible. Having pushed and insisted, I see that what I am up against really is impossible- although one builder specifically said that 16.2" is doable, without mentioning anything like wide bb shells or bent seat tubes.
    You guys are framebuilders- I am not. I came here for answers. I got them- what I want seems to be impossible. This forum is a place to share information among people in the know- but I also thought I would take advantage of its secondary service, to give information. Sorry for ruffling any feathers."
    "Pushing and insisting" would not be the recommended method as a layperson to approach a professional, especially if you don't provide any fit parameters, don't do any drawings, etc.

    I actually think that it is unprofessional for a designer, for when asked 'what is possible?' to even indulge that with an answer without asking for context. It's like going to a doctor to tell them what's wrong with you, after phoning a couple of other doctors and asking around on the internet.

    Justification for design does not begin and end with "because I want it".

    Uphiller, if you're really interested in design solutions based on something rather than hyperbole, tell us about your physiology. Give us your basic fit parameters, your fitness and flexibility. Tell us about the frames you have / had and what you liked / disliked about them. Tell us about where you ride, how you ride. Do you race?

    Nobody can make any reasonable statement about how long your chainstays should or shouldn't be without this basic information.
    No longer member of the bike industry nor society, so don't hassle me.

  93. #93
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    Quote Originally Posted by Thylacine
    The absolute limit is actually the wheel diameter, plus half the dia of the BB shell, plus 1mm. Nobody is BSing anybody - 415 is what I built based on THE WHOLE PICTURE. Who here has actually bothered to draw anything up, and who has arrived at a chainstay length based on anything but plucking a random "The smaller the number the better" out of the sky?.




    You do have comprehension issues. Your quoting proves my point - no talk of physiology AT ALL. THE MAJORITY of the frame geometry is FIT, and yet, yet no talk of fit at all. From anyone.

    The only useful bit of information Uphiller has provided is that he prefers shorter stays "because it's easier to lift the front wheel". Correct. Aside from the fact that we have no physiological paramters to make any statement regarding how short would be necessary for this, and because of this, the thread denigrates into "How short can we go!" like a high school playground debate, and because there is no design rigor, we're now looking at e-stay bikes being commissioned. Overwhelming evidence they don't work and are unnecessary. And yet, here we are.



    You're either with us or against us, huh?

    I don't know how old you are, but there really isn't any 'new materials' that would make an e-stay bike work, and certainly none that can defy the laws of physics to the point where you can literally just do the exact same designs that were done 15 years ago and somehow they will magically work. They've been made in carbon (Trimble) Titanium (Merlin) and steel, but YET AGAIN, if you don't have any context over and above 'coz I want it', you're still a solution looking for a problem.

    Maybe 16.75" would be enough for Uphiller? Maybe 16.5? At this juncture, who knows?



    "Pushing and insisting" would not be the recommended method as a layperson to approach a professional, especially if you don't provide any fit parameters, don't do any drawings, etc.

    I actually think that it is unprofessional for a designer, for when asked 'what is possible?' to even indulge that with an answer without asking for context. It's like going to a doctor to tell them what's wrong with you, after phoning a couple of other doctors and asking around on the internet.

    Justification for design does not begin and end with "because I want it".

    Uphiller, if you're really interested in design solutions based on something rather than hyperbole, tell us about your physiology. Give us your basic fit parameters, your fitness and flexibility. Tell us about the frames you have / had and what you liked / disliked about them. Tell us about where you ride, how you ride. Do you race?

    Nobody can make any reasonable statement about how long your chainstays should or shouldn't be without this basic information.

    He never asked how long anyone thought his chainstays "should" be! He knows himself, he knows his riding style, his location, etc. You. Don't. Need. To. There is no talk of fit because noone is asking you to fit them to a bike in this thread. Noone is looking for you to tell them what they need. A handful of people are looking to find the lower practical limits of a design to see what it will yeild. You don't know what it will yeild. You've got a pretty good guess, but it's really no better than anyone else's. Stupid/crazy ideas on this forum are usually met with "build it and come back to us". People have done that. Now you're having a hissy fit because you think it shouldn't have been done...

    There is no universal, inherent flaw in an elevated chainstay that means it will fail or flex. Several people have posted examples of 20+ year old e-stay bikes that are still being ridden on a regular basis. There is no reason why it can't be made to work, and utilized to achieve the desired results of those utilizing it. Full suspension was largely abandoned in the early 1900's. Is that good evidence that it should not have been brought back in the 80's and 90's?

    Lemme know when you come up with something else that wasn't asked for to complain about.

    I would like to keep this thread somewhat civil though because I think there's still some valuable, relevant info to be generated by the people involved with it. I would rather not see it locked for devolving into a slap fight. It's clear you don't like what this thread is about. Why not ignore it? Let it go. Stop trying to stir the shlitz.

  94. #94
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    Yep, that's a fair call. I realise nobody is asking for fit advise, however I'm attempting to illustrate that it's a pointless exercise attempting to find the lower limits because it has absolutely no design rigor. It's also been done to death, recently. As has elevated chainstays, which do have an inherent design flaw, commonly referred to as 'ignoring the laws of physics'.

    What is your design technology Groundhog Day limit?

    I liked your 1900's bike technology example. I'm currently designing a suspension system made from air and foam, because I wanted to see what the limits were. I'm pretty sure 29" wheels will make it b¡tchin'.

    Last edited by Thylacine; 05-15-2011 at 06:26 PM.
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  95. #95
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    Uphiller asked-

    What, really is the absolute minimum on a 29er if we pull out all the stops?
    Thylacine's answer-
    The absolute limit is actually the wheel diameter, plus half the dia of the BB shell, plus 1mm.

    29" + .75" + .04" = 29.79"

    So the correct answer is 29.79 inches and no less.

  96. #96
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    Let me make something that had been implicit, explicit: I don't necessarily believe that the minimum number is the right one for me. I didn't say it anywhere, although it is easy to see why someone would conclude that. I was interested in the minimum limit, and a discussion about what it would yield, as Sean put it, and not necessarily implementing it for me.
    Also, I have been out of the loop since 2003 or even earlier as far as new developments go. When this thread started, I had heard of 100mm bb shells but did not know there were XC-style cranks available for them, and had definitely never heard of an 83mm bb shell,and that was another thing that I did not state clearly: "How short can you get it with a 73mm bb shell?". So I was thinking in the box, and this thread, across the noise, has expanded that box and with that in mind, let's all keep talking.
    I am not looking to be fit.
    For what it's worth, I am 5'11" with a 32" or 33" inseam.
    The bikes I have liked to ride most are a trials bike I had, a steel 26-24 machine with 15.5" stays, a 2" travel Manitou fork, 170mm cranks, a 39" wheelbase, 70 degree head angle, and a 13" bb height. The best hardcore trials riders use long bikes now- 1080mm wheelbase and a 13.5" bb, low bars, etc, but honestly I am not talented enough to get one of those bikes' front wheel off the ground, and my old C6 disc problem in my neck makes me not want to try. Acceleration was rad, and really, to keep the front wheel on the ground, I had to put a 120mm stem on it. Of course, it was never an XC machine, but it started my interest in short stays.
    The steepest stuff I have done was actually on a 1995 KHS Team, which I got when I was 16. The reason I was able to do such steep stuff on it was A) being 18 B) the total length of the thing, 16.9" or so stays notwithstanding, was short. Short bike = ability to get behind the bike on steep stuff.
    The only bike I have ever really been happy with in terms of fit and multi-role adaptability is my Teasdale- 16" stays, 75mm stem, 12.75" bb height, clearance for a big tire, triple chainrings, maximized standover clearance. For awhile it had a 2.3" Tioga DH tire, a real monster, for doing trials, which was awesome on bumpy terrain- the bike just plowed over everything because of the large diameter and low pressure, and even so, it could easily be bunnyhopped over a log. Because of the rearward weight bias it can feel like it wants to tip over backwards, but I gave it a 74deg seat angle, so in seated climbs some of that bias is eliminated. And I have never been in a situation where I couldn't stand up and lean over the front on really steep stuff.
    A 29er with short (15.75- 16.25"?) seems like a way to get that juggernaut, roll over anything feel. It would be more unstable than a normal 29er, but the big wheels make up some of that difference. The whole concept is to combine as much as possible of the bikes I have liked best, and add something new, namely, big wheels.
    As for where I ride, I can say it can be almost anywhere, just not in big mountains with long straightaways demanding stability and/ or long travel. We could call it "East Coast".
    _

  97. #97
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    Quote Originally Posted by Thylacine
    Yep, that's a fair call. I realise nobody is asking for fit advise, however I'm attempting to illustrate that it's a pointless exercise attempting to find the lower limits because it has absolutely no design rigor. It's also been done to death, recently. As has elevated chainstays, which do have an inherent design flaw, commonly referred to as 'ignoring the laws of physics'.

    What is your design technology Groundhog Day limit?

    I liked your 1900's bike technology example. I'm currently designing a suspension system made from air and foam, because I wanted to see what the limits were. I'm pretty sure 29" wheels will make it b¡tchin'.


    Wow. Completely different edit from what it originally said.

    My design technology groundhog day limit is till the latest design(utilizing materials suited to the end use of the product) succeeds flawlessly. Never gonna happen.

    Your base of physics knowledge has a pretty good chance of being better than mine. Explain in more detail than 'It just wont work' or 'it will break', why elevated chainstays are doomed to fail or flex excessively. Particularly the ones mentioned in this thread that haven't failed or flexed excessively.... I read your theory that the constant compression and rebound of the stay during pedalling would be the culprit, but that obviously hasn't effected the bikes mentioned.

    Even the Yeti's apparently all failed at the dropout, which doesn't suggest the e-stays were the culprit. Sure e-stays generally require a more compact rear triangle, but so do small and extra small frames. Dropouts aren't failing on those left and right.

    The compression and rebound forces at play on a bike should be in line with the section of chain pulling from ring to cog, right? The top section of chain. So wouldn't mounting the stays a couple of inches above a single chainring have the same effect as mounting them a couple of inches below, at the bb?

    Is it the width of the mounting area at the bb shell? Seems like it wouldn't be that much more difficult to add a lateral section of tube to the seat tube where the e-stays meet it. Or, as done on many of the surviving e-stay bikes, bend and extend the stays to meet the down tube and add a support bridge or plate at the seat tube.

  98. #98
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    Sean, the reason we don't see modern day e-stay bikes is exactly that - that the designs are flawed. I'd put good money on Ade's Chinese sourced frame lasting about a month under one of my hard charging expert class racers - if that. Sorry Ade, just my ATMO, don't take it personal.

    Honestly, any historical examples that still exist are either absolute pigs, have been babied, or are just plain lucky. Historically - and the fact that nobody makes a production e-stay bike anymore - hints at the issues with the design, but the biggest factor to their non-existence is that you can get super-short without having to resort to them.

    The main problems as far as my meager design knowledge are the unsupported BB, and the chainstays which go from being largely a compression member to being one in bending - and experiencing exponentially higher loading. I'm not an Engineer, so maybe someone can put some actual chain-load figures in there.

    The Yetis are a bad example. As I understand it (I could probably email Frank and ask the finer details but I'm too lazy) early ones did crack at seat tube until a gusset was added, and to say the Ultimates were heavy was an understatement - an average size one was over 5lbs. The bent downtube is also a bad design - again, because the torsional forces between the BB and headtube need to be counteracted, and a bent downtube doesn't do this efficiently. It does however, look good.

    Essentially, you just don't need e-stays - they create more problems than the solve. I don't know any of the regular designers on here would disagree.
    No longer member of the bike industry nor society, so don't hassle me.

  99. #99
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    Quote Originally Posted by merk
    What, really is the absolute minimum on a 29er if we pull out all the stops?
    Thylacine's answer-
    The absolute limit is actually the wheel diameter, plus half the dia of the BB shell, plus 1mm.

    29" + .75" + .04" = 29.79"

    So the correct answer is 29.79 inches and no less.
    NOPE The wheels radius not diameter so 14.5 inches not 29 inches so 15.29?
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

  100. #100
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    no offence taken , this bike is really something to test a few ideas.. and any comments good or bad are welcome

    it did take the company 5 months to deliver and spending 5 months looking at the drawings there is a number of points i would like to change,,

    i think trying to make it a do all in terms of gear setup was a mistake and bringing the chainstays down towards the BB will help, ..and junking any front mech mounting

    i love the way it rides it is nimble and tracks really well , it has more than 10mm clearance between the 2.4 tyre and any part of the frame which is great for the conditions we have in the UK

    I am drawing up V2 to narrow the dropouts and hopefully add some stiffness,

  101. #101
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    Quote Originally Posted by Thylacine
    Sean, the reason we don't see modern day e-stay bikes is exactly that - that the designs are flawed. I'd put good money on Ade's Chinese sourced frame lasting about a month under one of my hard charging expert class racers - if that. Sorry Ade, just my ATMO, don't take it personal.

    Honestly, any historical examples that still exist are either absolute pigs, have been babied, or are just plain lucky. Historically - and the fact that nobody makes a production e-stay bike anymore - hints at the issues with the design, but the biggest factor to their non-existence is that you can get super-short without having to resort to them.

    The main problems as far as my meager design knowledge are the unsupported BB, and the chainstays which go from being largely a compression member to being one in bending - and experiencing exponentially higher loading. I'm not an Engineer, so maybe someone can put some actual chain-load figures in there.

    The Yetis are a bad example. As I understand it (I could probably email Frank and ask the finer details but I'm too lazy) early ones did crack at seat tube until a gusset was added, and to say the Ultimates were heavy was an understatement - an average size one was over 5lbs. The bent downtube is also a bad design - again, because the torsional forces between the BB and headtube need to be counteracted, and a bent downtube doesn't do this efficiently. It does however, look good.

    Essentially, you just don't need e-stays - they create more problems than the solve. I don't know any of the regular designers on here would disagree.

    Thanks for the honest answer, and we agree on at least one thing regarding e-stay bikes: They look awesome...

    http://forums.mtbr.com/showthread.php?t=590280

    Regarding weight, was 5-6lbs not common for trail bikes back then? Seems the ones designed with really short stays were designed with tight/technical riding in mind more than racing or fireroad bombing. 'East Coast' if we use a US-centric term.

    So, you kinda said that it could work, if you can live with a small weight penalty.

    Problems it solves:

    Chain suck
    Removing chain
    Belt drive
    Short stays where desireable without going to using plates.
    Allows narrower q-factor where desireable.
    Allows any combination fo front chainrings desireable, outside of maybe a 70t in the granny position.
    Increased mud/debris clearance.

    Problems it creates:

    Need for reinforcement to mitigate flex and counteract the higher leverage forces on either end of the e-stay.


    Problems it doesn't solve on a 29er:

    Seat tube is still in the way of really short stays.

    ----

    Is a plate design any easier to fabricate than a sturdy e-stay? D.F.L. has a pretty signifigant upcharge for short stay 29ers due to all the additional fabrication work involved to make it durable.



    .

  102. #102
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    The pic is old, but Mrazek appears to still be producing e-stay bikes.
    http://www.mrazek.com/fx.html
    _

  103. #103
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    Wow – it has been busy on here….

    What do the Poms want to achieve by building E-stay frames? I was quite hoping it would annoy an Australian – looks like mission accomplished :-)

    So as requested - some context. I’m 65kg, 5ft 10 and singlespeed up and down in steep slippy places. So I climb a lot standing up at full grunt – shorter stays mean more of my puny XC er body weight is on the back wheel for traction. And I don’t tend to break bikes. Ever.

    I don’t like the handling of the production 29ers I’ve tried (long back end, steep head angle). But slacken the head / increase fork rake and the wheelbase gets huge and the whole bike feels (to me) sluggish. So a short back end means I can have a long front and a sensible wheelbase. But I don’t know how short is the optimum for my height / weight / riding. So instead of blowing hot air on forums I’m making a bike with a back end that can be adjusted over a big range. And using E-stays means I can play with the back wheel position in all permutations (right up to 5mm from the bb shell / curved seat tube – not that I consider this position to be of much use – I just did it because I could – is there anything wrong with that?).

    I’m fully aware what a wonderful thing the conventional diamond frame is – but to give the above adjustment range would need some major surgery of conventional stays and oddball shells / hubs / q factor / whatever that I don’t want to use.

    Bending fatigue failure of the chainstay can happen. But the lower the chainstay the less the bending. I’m also only running a medium front ring which means less chain tension and hence less bending / compression of the stay (compared to say a 22t granny ring). I've worked in a fairly impressive automotive fatigue test lab for the last 20 years so have a reasonable understanding about durability and how things break.....

    As you allude, the chainstay becomes a cantilever beam in an E-stay design (albeit one that is triangulated quite effectively by the seatstays). And you never find cantilever beams under cyclic fatigue loading anywhere else in bikes. Except seatposts….and handlebars…..and stems…..and forks…..and bottom brackets….and pedals…….

    I thought this forum was a place to ask questions and show ideas / generally encourage people to make their own stuff – did I get something wrong?

  104. #104
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    Yes!

    Some of us can be prickly, but yes, anyone who wants to build bikes is welcome here, no matter how dumb some of us think the idea is (FWIW, it's not that hard to get <16" stays without going to e-stays or a weird BB on a 29er singlespeed - think "outboard chainring position").

    So build weird stuff, and if it sucks, tell us about it. If it rocks the party, tell us about that too! I am certain we have all made our share of bikes that turned out pretty worthless - so there is no shame in trying something new (or something that's been done and discarded, like e-stays) just because you want to see what it's like.

    There has been a lot of useful info in this thread - let's not let it bog down into sniping, eh?

    -Walt


    Quote Originally Posted by mickuk
    I thought this forum was a place to ask questions and show ideas / generally encourage people to make their own stuff – did I get something wrong?

  105. #105
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    Quote Originally Posted by mickuk
    I just did it because I could – is there anything wrong with that?).

    I’m fully aware what a wonderful thing the conventional diamond frame is – but to give the above adjustment range would need some major surgery of conventional stays and oddball shells / hubs / q factor / whatever that I don’t want to use.

    Well, just tell us how it hangs in there. I am a bit surprised you built this out of metal. It does seem like a design that would be better realized in composites and the difference between then and now is that we have a much better understanding of how to use them and they have become more user friendly.

  106. #106
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    Quote Originally Posted by sean salach
    Problems it solves:

    Chain suck

    .
    only partly. Chain suck can still happen. Just that the chain can not jam between rings and chain stay. Having the chain get stuck in the frame is a result of chainsuck, not chainsuck itself.

    I have been there. Chain stays stuck to the ring until it contacts the top run of chain.
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  107. #107
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    I was googling "e-stay". Is this aprox. 16.5" chain stays?

    http://www.spanner.org.uk/2011/05/ga...frame-by-xacd/

  108. #108
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    e= short for elevated chainstays.
    https://www.google.com/imgres?imgurl...1t:429,r:5,s:0
    _

  109. #109
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    Sorry, I know that now. I was pointing to the web page which has a drawing for a bike ... posted yesterday. I think the effective stay length is about 16.45 inches but I am not really sure how to read the blueprint.

    Adrian’s radical prototype e-stay titanium 29′er frame by XACD

  110. #110
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    Quote Originally Posted by shiggy
    only partly. Chain suck can still happen. Just that the chain can not jam between rings and chain stay. Having the chain get stuck in the frame is a result of chainsuck, not chainsuck itself.

    I have been there. Chain stays stuck to the ring until it contacts the top run of chain.

    Good point. I mistyped that. "Frame damage caused by chain suck" would have been much more appropriate/accurate.

  111. #111
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    Quote Originally Posted by merk
    The absolute limit is actually the wheel radius, plus half the dia of the BB shell, plus 1mm.
    Technically, Its the cranks axle radius instead of the BB shell. You could cut an arc into the shell for a tiny bit more room.

  112. #112
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    Let's not forget that Trimble still makes e-stay bikes!


  113. #113
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    /\ Those e-stay bikes look like this:
    Attached Images Attached Images  
    May the air be filled with tires!

  114. #114
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    They don't look like that at all. They look nice! Unfortunately they behave like the picture!
    But carbon is/should be the way to go for e-stays. How about big fat titanium stays. They should be able to handle the flexing...

  115. #115
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    Edit: said too much. Must remember my Resolution...
    Last edited by D.F.L.; 05-18-2011 at 07:26 AM.

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    well version two of my estay 29er is drawn
    i have made a few desisions

    i have decided not to run a FD that way i can drop the chainstay lower on the seat tube

    I am currently running 8 speed alfine or single speed

    my adjustable dropouts were 417mm +20mm of adjustment by dumping any idea of running a FD means i can now change the adjuster to be 417mm + of - 10mm which gives me the option of running chainstay length of 407 to 427 ,

    I am changing the headtube to a tapered one as i like the look

    dropouts have changed sort of inside out which saves about 20mm in width either side

    new adjuster for dropouts

    not sure about pressfit BB yet but looking into options

    bigger downtube

    should keep the little man in China busy for a while

  117. #117
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    650b or assym stays.. elevated drive, regular non. I think Brave did this. Also Vulture has made a few Valkyrie style frames with updates such as discs, and larger tubes. I'm sure he'd share his thoughts.

    Or pull a Pong and have stays on one side only!


    -Schmitty-

  118. #118
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    i keep going back an looking at asymetrical chainstays for this bike,, but dont feel happy with a design that is stiffer on one side than the other, and any flex would cause the wheels to go out of line

    I know people will say lefty etc

  119. #119
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    Bikes are pretty assym as is with the drive all on one side. I get your drift, but think your over thinking it unless you have legs of Heiden and lungs/dope of Armstrong.

    -Schmitty-

  120. #120
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    over thinking thats something I have never been accused of doing before

    it all depends on peoples definition of too much flex,, currently it doesnt throw its chain and as i have huge clearence between the tyre and the frame you will never get the tyre to rub
    but it is not stiff enough to run a belt drive

    just how stiff does a frame need to be?
    everything must flex to some degree how much is acceptable I think i may start a new post

  121. #121
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    Reviving this thread but going back to original idea (short stays, not e-stays).

    Has anyone ever tried moving the cranks back by using the BB as a jackshaft, thereby allowing you to move the wheel forward and under the seat more?

    Obviously tons of problems it would create - traditional front trianlge would become difficult, wide Q factor and/or prohibit wide tires as chainstays and seatstays would have to be narrower to allow cranks to pass, heavier due to more parts, having to replace parts in pairs as drivetrin wears, slop in the system from the addition of more cogs/chains, only able to do as SS or 1x8/9/10?

    Handling would be quite different depending on how far forward you moved the wheel.

    So perhaps not realistic but thought it would be interesting to see it done or tried if someone were wanting to try and get REALLY short stays.

  122. #122
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    Quote Originally Posted by mbeardsl View Post
    Reviving this thread but going back to original idea (short stays, not e-stays).

    Has anyone ever tried moving the cranks back by using the BB as a jackshaft, thereby allowing you to move the wheel forward and under the seat more?

    Obviously tons of problems it would create - traditional front trianlge would become difficult, wide Q factor and/or prohibit wide tires as chainstays and seatstays would have to be narrower to allow cranks to pass, heavier due to more parts, having to replace parts in pairs as drivetrin wears, slop in the system from the addition of more cogs/chains, only able to do as SS or 1x8/9/10?

    Handling would be quite different depending on how far forward you moved the wheel.

    So perhaps not realistic but thought it would be interesting to see it done or tried if someone were wanting to try and get REALLY short stays.
    Add to that list: tensioning the additional chain or belt.

    I've thought of it for E-stays that would allow for people that experience knee problems with wide Q factor setups to ride a fat bike.

    Obviously the niche there would be tiny: someone who has ridden a fat bike, got injured from the knee angle while pedaling, and really knows what he wants.

  123. #123
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    Quote Originally Posted by Drew Diller View Post
    Add to that list: tensioning the additional chain or belt.

    I've thought of it for E-stays that would allow for people that experience knee problems with wide Q factor setups to ride a fat bike.

    Obviously the niche there would be tiny: someone who has ridden a fat bike, got injured from the knee angle while pedaling, and really knows what he wants.
    Interesting idea. Move the stays up and out of the way and in essence build a half stay that the cranks would attach to?

  124. #124
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    Interesting on the jackshaft front - especially for super fat tyres. I guess you still want a pair of cranks and bb in the same place, so that kind of limits how far forward the wheel can ever go (and I can already set the dreaded e-stay bike up with tyre 5mm from bb shell without needeing a jackshaft).

    A few months on and the e-stay rides great - I'll update the build post soon. However, like all projects I want to build another frame over winter, and the "open plan" nature of the bb area on the e-stay frame gives a great working model for trying out regular stays in unusual bends / sizes / joints. So I've now got some ideas for other ways to squeeze short stays in there without resorting to elevation / big q factor........

    Anyway - it is summer and mk1 ultra short stay 29er needs some miles before I go building anything else (24hr race this weekend, then 2 weeks in Germany / Swiss alps - hopefully it won't break!).

  125. #125
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    Quote Originally Posted by mickuk View Post
    I guess you still want a pair of cranks and bb in the same place, so that kind of limits how far forward the wheel can ever go.
    No, well yes. And no. The whole point of using the bb as the jackshaft is that you can move the wheel wherever you want.

    NOTE: I am not saying this has ANY real world applications/justifications/etc, just an interesting idea (to me).

    My graphics skills are lacking so I'll try and explain. Imagine taking a standard rear triangle. Remove cranks and put a small cog on each end of the spindle (same size). Beef up the chainstays so that you can mount the cranks mid-chainstay using half of a bottom bracket (hence the wide Q factor unless chainstays came in towards the wheel significantly which is prob not structurally good). Put a chainrings on each crank (same size) and connect to the cog on the bb spindle with a chain on each side.

    So now you have two cranks mounted wherever you want along the chainstay, put in sync using a chain to the forward bb on each side of the wheel. Link the dirve side crank to the rear hub to drive the rear wheel. The non-drive side mess is simply there to keep your cranks at 180 deg from each other which would result in some slop given all of the cogs/chains/chainrings.

    Now imagine moving the forward bb forward in relation to the rear axle, taking the seat tube with it (bending around the wheel so the seat remains above the cranks), taking out the slack in the seatstays. Goofy, heavy, lots of parts and pieces, likely impractical, wide Q factor etc etc, but make your chainstays 14", 7" or anywhere in between. You would eventually approach something that resembles a unicycle with a front wheel (reverse penny farthing?) as you move the wheel forward.

    See image below for a terrible drawing.
    Attached Thumbnails Attached Thumbnails Short-stay 29ers- the limit?-jackshaft.jpg  


  126. #126
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    Wow - cranks on stub axles - now I understand. Apart from wheel size I don't think that really counts as a 29er :-)

    Have a look through some old bike photos - you'll probably find something similar has been made in the past (I've certainly seen penny farthings with chain drives and jackshafts.

  127. #127
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    Quote Originally Posted by mbeardsl View Post
    No, well yes. And no. The whole point of using the bb as the jackshaft is that you can move the wheel wherever you want.
    Hmm... With a fixed gear, you could skip the jackshaft, and just gear to both sides of a flip-flop hub.

    Or skip all that business and just do this:

  128. #128
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    Just got back from single speed world champs with my e stay bike,,
    it's still in one piece and riding well
    the bb is a bit flexy but the chain stayed on and it didnt skip or jump at any time ,
    the short wheelbase and short chainstays make it great on the singletrack ,

    Version 2 drawing is now in china and new frame should be here in about a month
    changes inc
    narrower rear dropouts
    50mm down tube i am keeping with the curved downtube as this gives me fork clearence without the swanneck in the top of the downtube normaly used to clear fork crowns
    chainstay has been lowered down the seat tube
    tapered headtube

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