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  1. #1
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    |Ideal chain stay length for tight single track

    Question for those of you with lots of expierence.

    In my last meeting with my frame builder (for my new steel SS29er) he told me that he almost always uses 45cm lenghts for his chain stays. Said that its "the sweet spot"

    i have read some post's hear about using shorter stays for better handling

    I asked him about going shorter as I ride tight single track almost exclusivley. He was aprehensive and told me to do some research before our next meeting.

    He is a mechanical engineer and i dont what to go against his expierence unless i have good reason.

    Any thoughts on going shorter, I know that a number of popular factory steel 29ers have shorter stays than 45cm.

    Also, the bike will be running a split shell EBB.

    Thanks
    Last edited by Mo$ey; 08-21-2010 at 08:36 AM.
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  2. #2
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    I'm thinking you mean 450 or 455mm, because 45mm=1.8", and my math may be off, but last I checked you can't fit a 29er wheel in that length of chainstay

    All joking aside...I ride a Black Cat with a sub 17" chainstay. It handles the tight singletracks better than any bike I've been on. It is awesome, and I can't say enough great things about how nice it handles. Do note, however, that chainstay length alone doesn't account entirely for handling. It's the combination of tube lengths and angles that give a frame it's handling characteristics, which is something to consider if your frame builder isn't accustomed to building frames with short chainstays. That is one of the reasons I went with Black Cat. He regularly builds 29er frames with short chainstays.

    Although the short chainstays do help in carving through fast singletrack, there are some minor drawbacks I've noticed. Since I sit over the rear wheel axle more, I feel more of the bumps on the rocky stuff. The bike is a little more twitchy in the technical sections, but I can still keep it very much under control. Also, I think that because of the shorter overall wheelbase, it takes less movement in body position to shift weight forward and back. Where I've been use to making more drastic body shifts forward and back for the technical stuff, now I've had to get use to making small shifts in weight, if not I loose traction or bring the front up more than I want...things like that.

  3. #3
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    45mm that is short!

  4. #4
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    Short CS are nice on 29ers as well as running fat rubber imho. An EBB will limit this combination a bit. I have a few bikes with short stays and EBB. Only downside I've had thus far has been CS clearance requiring the rear tire to be shaved on the sides a bit. Think mine are right at 425mm

  5. #5
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    Quote Originally Posted by Mo$ey
    Question for those of you with lots of expierence.

    In my last meeting with my frame builder (for my new steel SS29er) he told me that he almost always uses 45mm lenghts for his chain stays. Said that its "the sweet spot"

    i have read some post's hear about using shorter stays for better handling

    I asked him about going shorter as I ride tight single track almost exclusivley. He was aprehensive and told me to do some research before our next meeting.

    He is a mechanical engineer and i dont what to go against his expierence unless i have good reason.

    Any thoughts on going shorter, I know that a number of popular factory steel 29ers have shorter stays than 45mm.

    Also, the bike will be running a split shell EBB.

    Thanks
    Depends on the total geometry package. No one number defines the bike. It also depends on rider size and riding style, but few builders look at that.

    I like my stays around 445mm, even with 26" wheels.
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  6. #6
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    Quote Originally Posted by julioardz
    I'm thinking you mean 450 or 455mm, because 45mm=1.8", and my math may be off, but last I checked you can't fit a 29er wheel in that length of chainstay

    Sorry, Late night. I meant to say 45cm
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  7. #7
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    There is not a "sweet spot"

    ...at least for all riders and terrain. There's arguably a sweet spot for any given rider on any particular type of trail, but even there - ride the super long stay bike in the twisties, or the super short stay bike in the fast rough stuff, and they're not so ideal anymore.

    Like anything, it will be a tradeoff, and where you want to make that tradeoff will depend on your size, riding style, terrain, and intended equipment (especially drivetrain and tires, which will be limited at certain lengths).

    Many manufacturers (and builders) don't want to deal with cramming big tires into short stay bikes, because it's a lot of extra work and you've got to plan everything pretty carefully. Others cram everyone onto the shortest stays they can regardless. Both of those approaches, IMO, are pretty dumb.

    If you're not sure, have the builder use sliding drops or swingers - you'll have 20mm or so of chainstay length adjustment that way. Doing a gravel road ride? Slide 'em all the way back. Riding Earl's or the Kingdom? Slide them forward as far as you can.

    You can do this to a limited extent with an EBB, but the adjustment range is much more limited and you'll possibly have to move your saddle around to keep the pedals in the same place. If you're aiming for really short, the EBB will also make things a bit more difficult for the builder (explaining would take forever, you'll have to take my word for that part).

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  8. #8
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    Mine are 450 on a medium frame and it is absolutely nimble in the tight stuff and stable in the fast stuff as well as climbs like a goat, it happens to work extremely well for me. Combined with the rest of the frame geometry it absolutely ROCKS. Put these stays on a frame with different geometry and I might hate it. Gotta look at the whole package.

  9. #9
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    i owned / tested a lot of bikes in the years, including a Banshee paradox and a Tallboy (very short CS) and a Salsa DosNiner and a GF292 (Very long), and made some experiments with the sliding dropouts on a Karate Monkey.

    Short CS are good to unload the front (manual), but that can be problematic while climbing (you really need to sit on the tip of the saddle and get low).

    There is another effect that few people talk about. While puting the rear whell forward shortens the whellbase, it also puts more weight on the rear, and less in the front (balance). So on one side you quicken the ride, but on the other you unload the front, leading to understeer. So depending on the rest of your setup you can feel one of the effect more than the other....

    For race car engineers, this is a setup wich is use with inboard and outboard toe in. Using the same toe in, In board toe in shortens the rear. In this example, a short "chainstay" gives a slower (less twitchy) car ! You can also experiment this on a competitive RC car (RC10 B4....)


    So for your needs, i would mainly focus on the front end, with a geometry that puts a lot of weight on the front tire, and a short trail. This is the most important !

    As for the rear, you will be able to use short chainstays without troubles going uphill because on a singlespeed one climbs standing, puting more weight on the front. As the frame is singlespeed only, short CS are simple to build for the framebuilder (without EBB like Walt said, i hate EBB ! and would go for a BB92 of BB30

    I think Walt advise is very wise, ask your builder for sliding dropouts allowing 425 to 450, or get a Karate Monky which already provides most of the things you are looking for
    Last edited by 20.100 FR; 08-21-2010 at 10:48 AM.
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  10. #10
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    Through experimentation with sliding dropouts, I found I personally prefer a little longer stays.

    Yep, it's harder to manual and wheelie. But it you don't have to get as far out of an efficient position to weight the front tire for climing, the bumps seem less direct, and the bike is generally more stable and has better grip cornering. I have a hunch if I sat lower on the bike (30" saddle height), that I might prefer shorter stays.

    I agree that you you may want to consider sliding or swinger droputs.

  11. #11
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    I'm probably one of the more obnoxious short chainstay advocates. The only reason I like em super short is because I have a heavy trials and bmx(street) background. Super short suits my riding style and plays to my strengths. 17.7 seems pretty long to me. I would say for all purpose mtb, 17.2-17.5 would be more ideal for the average person. For the wierdo like me, I want something like 16.5-17.2 with sliders.

  12. #12
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    I noticed that the Niner frames that I looked at (AIR 9 and MCR 9) both had short chain stays relative to the salsa frames I considered. Interestingly they also had longer top tubes. I'm not sure why but the one learning curve issue I seem to be having is getting the rear tire weighted when pedaling over short steep steps. I'm spinning out and stalling. On the face of it, it seems like if the stays were longer that would be worse????

  13. #13
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    Quote Originally Posted by rideandshoot
    I'm not sure why but the one learning curve issue I seem to be having is getting the rear tire weighted when pedaling over short steep steps. I'm spinning out and stalling. On the face of it, it seems like if the stays were longer that would be worse????
    If you don't have problems with the front whell going up, and problems of grip in the rear,
    then you can use a more rear based weight distribution with shorter chainstays.

    But as always the rider is more far more important than the bike, and improving your technique is much more effective than buying new stuff
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  14. #14
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    I like em super super super short, probably because I ride the same trails Sean did when he lived in normal America
    I like my bottom bracket high too, not just for clearance but that's also a huge factor on how nimble the bike is.
    My simon bar is SHORT SHORT and pretty high up. Makes it unbelievably nimble, especially for a 29er.
    Though it does make it less than desirable for 5+ hour rides, the pedaling position is not very XC race. I could always throw a longer stem on it and move my seat forward but I can't give up how awesome it rides now.

  15. #15
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    Quote Originally Posted by shiggy
    I like my stays around 445mm, even with 26" wheels.
    Doesn't that Big Mama have much longer stays?

  16. #16
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    Quote Originally Posted by the_eleven
    Doesn't that Big Mama have much longer stays?
    Yes, but I have 8 other bikes. The Big Mama stays are long and I do not really have any issues with that. Do not want a hardtail/rigid bike with stays that long, though.

    I also have a 26 with 390mm stays and it is tail happy. Will try to swap ends on the slightest bump.
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  17. #17
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    Quote Originally Posted by 20.100 FR
    If you don't have problems with the front whell going up, and problems of grip in the rear,
    then you can use a more rear based weight distribution with shorter chainstays.

    But as always the rider is more far more important than the bike, and improving your technique is much more effective than buying new stuff
    Ya I think it could be a number of things, maybe the tire, maybe going from a full suspension 26er to the HT 29erů just something to get used too.

    I am intrigued with the subject though because prior to making the switch the Niner I spent time on a Ibis Ripley, a SC Super Light, a Kona Hei Hei and a PsycleWerks Wild Hare. The Psycle Werks has the longest stays and the longest Top Tube and I always felt dramatically more comfortable on technical (up or down) terrain on that bike.

  18. #18
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    I run 16.7 chainstays....of course I also ditched the boat anchor 29er rear wheel and run a 26"....that is.....a 69er frame

    I hated my 29er in technical singletrack and say what you will, with really technical twitchy stuff the 26" flicks better, more manueverable, accelerates better, and just sweet for such. I tried for 3 years and with some pretty light (23lb with suspension) 29er builds. Just can't fight physics in the end for such

    I do like 29ers, and building a rigid one soon with drops, but for the really twisty/technical, the 69er or the 26" 120mm travel rig are my favs.
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  19. #19
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    Quote Originally Posted by sean salach
    I'm probably one of the more obnoxious short chainstay advocates. The only reason I like em super short is because I have a heavy trials and bmx(street) background. Super short suits my riding style and plays to my strengths. 17.7 seems pretty long to me. I would say for all purpose mtb, 17.2-17.5 would be more ideal for the average person. For the wierdo like me, I want something like 16.5-17.2 with sliders.
    Pretty much ditto to everything here. I would not want a SS hardtail at 17.7", especially in tight terrain on a single speed. Fast sweeping terrain, yes. Extremely tall rider who prefers to sit in the saddle, yes. Teeny weenie climbing gears where the rider sits to climb, yes.

    Stand to climb Single Speed in tight terrain under a rider who likes to muscle the bike around? No, no, no.
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  20. #20
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    Quote Originally Posted by rideandshoot
    I am intrigued with the subject though because prior to making the switch the Niner I spent time on a Ibis Ripley, a SC Super Light, a Kona Hei Hei and a PsycleWerks Wild Hare. The Psycle Werks has the longest stays and the longest Top Tube and I always felt dramatically more comfortable on technical (up or down) terrain on that bike.
    Well, you have to take into account the angles too. For example a 1░ angle change in the seat tube implies a 1cm change in the lenght of the top tube, with the same reach. So comparing bikes with only the lenght of the top tube can be misleading.

    May be your Psyche as a slack seat tube, that gives a short reach even with a long top tube...
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  21. #21
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    (without EBB like Walt said, i hate EBB ! and would go for a BB92 of BB30
    I agree on the EBB; it is nothing but trouble.
    Also concur on the BB30. I would even improve and and go with FP30.
    I would not consider BB90/92 -- there is no benefit to that approach whatsoever.

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