Perfect chainstay length- Mtbr.com
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  1. #1
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    Perfect chainstay length

    Just wondering if there are any ideal chainstay lengths for a single speed.

    I run 20x32 and feel like I can never use the adjustable dropouts on my bikes. Most recently my last bike had a min chainstay length of 445mm and my current bike is 427mm. Even though they both have adjustable dropouts there is only 1 rand9m position in the sliders that works with single speed chain. If i take out a link the chain is way to tight and if I add a link then I can't tension the chain

  2. #2
    WillWorkForTrail
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    Those adjustable dropouts aren't there to change your chain stay length, they are there to tension your chain properly. That said, there is no idea chain stay length. It's a number that results typically from arriving at working solutions with other parts of the frame's geometry. A longer chain stay will result in a more stable ride, a shorter one in a slightly more playful ride. Some people complain you can't manual a bike with long stays, but I've never had that problem, and I've ridden (and owned) some of the worst "long chain stay" offenders, to hear some of the folks on MTBR have their say. I suppose the question is, do you feel confident in your bike at high speeds? Do you feel like you can't make your bike do the stuff you're asking it to do? Is there some glaring deficiency? Because "ideal" is going to come down to your opinion of how the bike rides.

  3. #3
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    You can change your chainring/cog and end up with a nearly identical ratio but a different length chain. Find a combo that lands you in the middle of your adjustable dropouts if you want.

    http://eehouse.org/fixin/formfmu.php
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  4. #4
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    my perspective is- the shorter, the better. sub-17" (~430 mm) chainstays are nice, but under 16.5" (~420 mm) might be ridiculous. but that's my subjective experience based on my height, weight, and riding style. other riders will want them much long and others much shorter.

    on any bike that uses adjustable sliding dropouts to tension a chain, you get what you get with the gear combo you chose. so if you think you have the "perfect" number in your head, you're going to be off by a little bit in the real world.

    also keep in mind- CSL cannot be taken in isolation. if you want to make the front end of your bike easier to loft, shortening the CSL is one way, but raising the BB, or shortening the reach to the bars can have a similar effect.

    a bike with a low BB and a long CSL is going to feel very stable, and might be preferred if you're tall, or if you're riding long distances with a loaded bike.

    but a long CSL with a very high BB might balance out. a high BB and a short CSL will be nimble indeed, maybe too much so, such that it will loop out and cause you to go OTB often. there's a balance and compromise to seek here.

    it is my opinion that a bike with a low BB ought to have a comparatively short chainstay as well, at least for the way I like my bike to handle.
    Last edited by mack_turtle; 10-12-2018 at 09:08 AM.

  5. #5
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    I run 30x18 on my Nimble 9, and I've run the dropouts both almost fully extended (~430mm) and almost fully slammed forward (~415mm). Adding or removing two links causes those results.

    I was surprised how much difference 15mm could make in the way the bike rides. The longer the chainstay, indeed the stabler the bike is at speed. Likewise, the shorter the chainstay, indeed the more "nimble" the bike is in general.

    Overall, though, I'd agree with above. The shorter the chainstay the better. Less chainstay = Mo' fun.

    Find the ratio you like to run, then try a few different chainring/cog combos with that approximate ratio that will allow the shortest chainstay.

  6. #6
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    I used the calculator above to get me pretty close and figure out what options I have given the ratio I like running. I like stays as short as possible...running my 2016 Nimble 9 fully slammed with 34 x 18.

  7. #7
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    I prefer my chainstays long enough to reach the dropouts from the bottom bracket...
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  8. #8
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    ... and if we just ...

    https://nsbikes.com/surge-evo,115,pl.html

    I asked can i tension the chain using sliding dropouts from NS.

    Answer: ”Hi'

    The answer is NOPE!

    Sorry you have to use chain tensioner”

    Can somebody explain me? I understand it might affect tire clearance.

  9. #9
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    Quote Originally Posted by stumpe View Post
    https://nsbikes.com/surge-evo,115,pl.html

    I asked can i tension the chain using sliding dropouts from NS.

    Answer: ”Hi'

    The answer is NOPE!

    Sorry you have to use chain tensioner”

    Can somebody explain me? I understand it might affect tire clearance.
    It sure looks like you could use the dropout to tension the chain but the only draw back is a lack of anything to lock the adjustment in, it might slip(it's also possible they have no clue what you're talking about). Being a steel frame though you should be able to get some good torque on those screws. If the 411mm stated chainstay length is in the slammed forward position(which the drawing seems to indicate), the next sweet spot looking on the eehouse fix me up site(https://eehouse.org/fixin/formfmu.php) is at about 415-416mm which should work nicely.
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  10. #10
    Rod
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    Quote Originally Posted by stumpe View Post
    https://nsbikes.com/surge-evo,115,pl.html

    I asked can i tension the chain using sliding dropouts from NS.

    Answer: ”Hi'

    The answer is NOPE!

    Sorry you have to use chain tensioner”

    Can somebody explain me? I understand it might affect tire clearance.

    My XTC is made very similar, but it has another bolt from front to rear as well. I circled the location of it in the pic below. I have no idea if it's needed and that's what I use to microadjust the chain and keep the tire straight. With a couple of steel bolts and that being a steel frame you could give it a shot, but I'm not sure if you want to risk it. The size of my bolt is roughly a 3mm allen.Perfect chainstay length-outerbike-moab-61-1200x803.jpg

  11. #11
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    Quote Originally Posted by nsbikes.com
    MAIN FEATURES:
    - designed for All Mountain, Freeride
    - high-end cromoly steel tubes
    - modern aggressive geometry (slack HA, low BB, long reach).
    - adjustable CS lenght via sliding dropouts
    I wonder if they mean it doesn't have enough adjustment to guarantee fitting a particular gearing.
    Yeah I only carry cans cause I'm a weight weenie.

  12. #12
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    Quote Originally Posted by AlexCuse View Post
    I wonder if they mean it doesn't have enough adjustment to guarantee fitting a particular gearing.
    If I fit the chain with sliders slammed forward theres a room to tension I presume.

    Just speccing a new steel ss frame.

  13. #13
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    Quote Originally Posted by stumpe View Post
    If I fit the chain with sliders slammed forward theres a room to tension I presume.

    Just speccing a new steel ss frame.
    You'll have a very limited combo of chainrings/cogs to chose from(without using a half link, but that rules out an NW chainring) but yes potentially.
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  14. #14
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    There looks to be plenty there to tension and you also don't really need a jam bolt to make it work, although you may find yourself tensioning the chain a *little* more than normal.

    I'd go into it prepared to need to try a couple different cogs in case my gear choice was at the extreme end of being long or short, but aside from that it will be fine.

  15. #15
    eri
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    Quote Originally Posted by mack_turtle View Post
    my perspective is- the shorter, the better. sub-17" (~430 mm) chainstays are nice, but under 16.5" (~420 mm) might be ridiculous. but that's my subjective experience based on my height, weight, and riding style. other riders will want them much long and others much shorter.

    on any bike that uses adjustable sliding dropouts to tension a chain, you get what you get with the gear combo you chose. so if you think you have the "perfect" number in your head, you're going to be off by a little bit in the real world.

    also keep in mind- CSL cannot be taken in isolation. if you want to make the front end of your bike easier to loft, shortening the CSL is one way, but raising the BB, or shortening the reach to the bars can have a similar effect.

    a bike with a low BB and a long CSL is going to feel very stable, and might be preferred if you're tall, or if you're riding long distances with a loaded bike.

    but a long CSL with a very high BB might balance out. a high BB and a short CSL will be nimble indeed, maybe too much so, such that it will loop out and cause you to go OTB often. there's a balance and compromise to seek here.

    it is my opinion that a bike with a low BB ought to have a comparatively short chainstay as well, at least for the way I like my bike to handle.
    Nice post.

    Besides ease of lofting front the shorter chainstays mean more weight on rear tread while climbing steeps, i can get max grip with a natural stance on bike. With long csl theres less weight on rear and i must hurk back on bars or the rear wheel slips. And slipping rear wheel while climbing is no fun at awl.
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