Thoughts on fat tires and frame clearance- Mtbr.com
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  1. #1
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    Thoughts on fat tires and frame clearance

    I love my steel SS 29er I currently ride, but wish it had more clearance for the exiwolf. (FYI- I try to keep chainstay length around 17.5 and get more clearance going longer, but don't like the ride with longer chainstay length). I am one rider who really wants bigger rubber to happen and I'll be first to get a pair of the new Kenda 2.35 and the other big "mystery tire" that is coming. So that being said...lets switch gears.

    I was considering getting a custom 29 frame for the sole purpose of enlarging the rear tire clearance. I was speaking with a very respected frame builder (who has built a few frames for people on this forum-I highly respect him) about this and his response to how can I get bigger tire clearance? was........ "tires shouldn't be that big - that company shouldn't have made that tire". Now first of all, calm down. I don't agree with him on this (I ride 2.3-2.5's on my 26in bike), but he has a point. Most (I'm sure not all, but most) custom framebuilders aren't able to get chainstays that are curved like surly or even niner. Apparently custom bending these things is way pricy and const prohibitive. So....how do custom frame builders expect to compete with the mass producing and manipulation that "volume" (relative speaking) companies like niner & surly can achieve using S bent seatstays and chainstays? (or plate assembly like Kona)

    I decided that I'd live with my "no clearance" exiwolf fit for the time being until I find a custom builder solution for this. A 29er tire with a casing the size of exiwolf but with real side lugs is awesome...as long as I can get a frame to fit it.
    Thoughts????

  2. #2
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    What about splaying them out a little more and dealing with a slightly higher Q factor? It seems like someone would make stays that are prebent, at least on the inside. I can see where having S stays would be difficult but having stays that are crimped on the inside seems like a viable option.

  3. #3
    kung food
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    There are most definitely custom solutions available.

    bicycling devices courtesy of Steve Stickel:

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  4. #4

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    My Vulture

    Was built to take wide tires last year before the Exi's came out. I was planning on running the fat Z-max's that never materialized...
    My frame fits Exi's easily with room for mud. I don't remember the CS length but it climbs like crazy. The only disadvantage is running a wide BB spindle for the low Q factor ENO cranks. I have a 127mm Phil steel BB and there is no flex or any issues...
    Now Wade did tell me it is hard to give a 29er customer everything they want at this point, but he never told me I couldn't have something that I want and is attainable...
    Call some more builders until you click with one. I like my guy
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  5. #5
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    They key to maximising tyre clearance is to really tune into what chainrings you're running - particularly middle ring.

    As a production bike designer, I have to let people run 38t middle rings and stuff. Which really eats up clearance at the crucial point on a 29er.

    If you were to design a SS frame around a spot rear hub (where the chainline is on the outer ring), with just a 32t ring, then you could get really big tyre clearance without a problem. With gears, it's possible, using bits of plate, funky bits like those two examples above, but they add quite a lot of weight. I know. I've done that sort of thing too.

    Finally I'd add that chainstay length is not half as important as most people think, and having ridden sample frames with short, indented chainstays (to get clearance), vs longer non indented ones, the longer back end was nicer in every way!

    I spend days at a time messing around with chainstay bend :-)

  6. #6
    mtbr member
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    They key to maximising tyre clearance is to really tune into what chainrings you're running - particularly middle ring.

    As a production bike designer, I have to let people run 38t middle rings and stuff. Which really eats up clearance at the crucial point on a 29er.

    If you were to design a SS frame around a spot rear hub (where the chainline is on the outer ring), with just a 32t ring, then you could get really big tyre clearance without a problem. With gears, it's possible, using bits of plate, funky bits like those two examples above, but they add quite a lot of weight. I know. I've done that sort of thing too.

    Finally I'd add that chainstay length is not half as important as most people think, and having ridden sample frames with short, indented chainstays (to get clearance), vs longer non indented ones, the longer back end was nicer in every way!

    I spend days at a time messing around with chainstay bend :-)

  7. #7
    mtbr member
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    Quote Originally Posted by Cloxxki
    Still, stuff from many expensive builders, on the 7th anniversary 29" tire, is still very cramped for even a basic 2.2" tire. Not good IMO. It's a bike, not a rocket.
    Yes - but unless the chainstays are 1.5in longer than a 26in frame, tyre clearance, with the same chainstay bend, will always be less.

  8. #8
    Recovering couch patato
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    If a custom frame doesn't clear the current range of tires, IMO that's a VERY bad sign. Either the builder was clueless on which tires exist, or he's just not willing to make the effort to make a 29"er that works as well as a typical 26"er (in terms of tire clearance).
    Current "wide" tires are all undersized. If a frame doesn't clear those well, how about a slight bit of gritty mud on a narrow 2.1"?
    A custom builder can't get chainstays shaped like on a KM? As above examples show, make it work, YOU're the professional framebuilder!
    I wonder if the customer's base demands for the frame didn't make clearance harder to manage. Still, stuff from many expensive builders, on the 7th anniversary 29" tire, is still very cramped for even a basic 2.2" tire. Not good IMO. It's a bike, not a rocket.

  9. #9
    College
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    i've seen walt works frames that can clear any tire on the market with a bunch of extra room for mud.

    http://www.waltworks.com/dev/gallery/Frames/Allan

    http://www.waltworks.com/dev/gallery...kes/Brian3_001
    College boy

  10. #10
    minister of chaos
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    The green ByStickel is my bike, and it has tons of clearance in the back. I've got plenty of room for a 3.0 should it ever arrive (and I actually want a tyre that big). The best part of it is that in addition, my stays are 16.7" long.

    frank
    Frank Tuesday
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  11. #11
    Alaska Turner Mafia
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    I wanted a 29er to accomodate SnoCat rims and the widest tire currently available, with some extra clearance in case larger tires eventually materialized. This notion was something Walt already had experience with, and accomplished for me also. Here's a photo of another way the clearance was achieved, shown with an Exiwolf on a SnoCat. As you can see there's quite a few examples of providing the clearance, just don't be so hung up on longer stays to get it. In my case one obstacle was eliminated, I'm not planning on running a big ring. With these examples shown it seems you've got plenty of choices. Pick your poison.

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  12. #12
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    good stuff

    Great discussion guys. But I guess I am hearing that plate is really the only true way to go. So the question is - why can't you guys have access to the same S - bent seat and chainstays that Niner, Surly, and I think IF use? Surly does tons of volume. That's probably how they pay for it (assuming they hard to make and do cost more like I am hearing). IF charges a lot - maybe that's how they pay for it. Is my logic correct???

  13. #13
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    Quote Originally Posted by jayoutside
    Great discussion guys. But I guess I am hearing that plate is really the only true way to go. So the question is - why can't you guys have access to the same S - bent seat and chainstays that Niner, Surly, and I think IF use? Surly does tons of volume. That's probably how they pay for it (assuming they hard to make and do cost more like I am hearing). IF charges a lot - maybe that's how they pay for it. Is my logic correct???
    You do not need S-bend seat stays to get clearance for big tires, especially if you do not use rim brakes.
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  14. #14
    mtbr member
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    Quote Originally Posted by jayoutside
    Great discussion guys. But I guess I am hearing that plate is really the only true way to go. So the question is - why can't you guys have access to the same S - bent seat and chainstays that Niner, Surly, and I think IF use? Surly does tons of volume. That's probably how they pay for it (assuming they hard to make and do cost more like I am hearing). IF charges a lot - maybe that's how they pay for it. Is my logic correct???
    No. Please read my comments again.

    Surly's rear stays are longer than some others - and they have conventional horizontal "track ends" - so a larger rear tyre can be accomodated by sliding the wheel back - up to 1.5in back? - in the track end. Hence - lots of room!

    Downside - problematic useage with disc brakes.

    It's not smoke and mirrors. It's just geometry.

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