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Thread: 40T Chainring?

  1. #1
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    40T Chainring?

    I saw that Gerry Pflug, the reigning NUE SS champ, won the Cohutta 100 running 40x24 this year. I thought my jump from 32t to 36t was pushing the envelope last year, I didn't realize people were going even bigger. Is anybody else running 40t+ up front? I feel like the reduced chainwrap of the bigger gear made a difference for me (and have cleared climbs that I couldn't before with smaller equivalent gearing), so I'm wondering if going even bigger will make a noticeable difference...

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  2. #2
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    My giant was a 42x19 that was a blast on the tour de wolf keep in mind i am on a 26'' wheel too.

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    Are you asking if running 40T will turn you into Pflug??

    I've just stuck with 32x20-ish, so I don't know about the "feel". I can't imagine it will give you any sort of advantage, though. Gearing is about the same on 40x24 (~48GI).

  4. #4
    more skier than biker
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    "bigger" chainring / cog combo's feel smoother to me, or more efficient or something. I don't know if this translates into any real world advantage, but I do notice a feel (i.e. I like how a 36x22 feels compared to a 32x20, even though they are a very similar ratio).

    Finding the bigger chainrings is pretty easy (i.e. a 40T, etc)...but I always seem to have a harder time finding cogs bigger than a 22T. Who makes a 23T, 24T, etc.?

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    Quote Originally Posted by Tyrone Shoelaces View Post
    ...Who makes a 23T, 24T, etc.?
    Endless Bike Company | Blowout Kick Ass Cogs

    Regular cogs are $40-50 and available in larger sizes.

  6. #6
    Eli Broccoli
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    I started running 34 or 36 and I noticed considerably less wear on chainrings and chains.

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    Yup I started running bigger rings last year, and noticed less wear on both front and back, and I like the increased chain wrap.

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    Quote Originally Posted by Tyrone Shoelaces View Post
    "bigger" chainring / cog combo's feel smoother to me, or more efficient or something. I don't know if this translates into any real world advantage, but I do notice a feel (i.e. I like how a 36x22 feels compared to a 32x20, even though they are a very similar ratio).

    Finding the bigger chainrings is pretty easy (i.e. a 40T, etc)...but I always seem to have a harder time finding cogs bigger than a 22T. Who makes a 23T, 24T, etc.?
    I did read an article that escapes me now, that did say there is an efficiency advantage with larger rings...whether it is noticeable I don't know.

  9. #9
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    when I finally settle on a spiderless crankset, I'm gonna order a 34t bling ring to go along with it! Started with 32/20, currently 32/18. 34/18 should be about perfect for me for most trails I'd imagine. At least most of the trails around me! 40 seems a bit excessive, but if you can push it go for it!

    There is someone around here who runs 36/16. Manbeast we call him!
    SS ==> Nut up or Shut up!

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    Quote Originally Posted by finch2 View Post
    I did read an article that escapes me now, that did say there is an efficiency advantage with larger rings...whether it is noticeable I don't know.
    For some reason, I can't get this through my head. Ok, so say you've got an enormous chainring--200T and the same crank length. With the gear ratio the same as 32x20 (125T in the rear), even without considering the weight, it would seem some mechanical advantage is lost, as the leverage arm is proportionally shorter.

    Any physics geeks want to chime in?

  11. #11
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    The physics is really just a very simple gear ratio. The ratio between the gears relates movement at the crank to movement at the rear wheel. Consider 22/11 and 40/20 if you divide the ring by the cog you get the number 2. On revolution of the cranks becomes two revolutions of the rear wheel. Both gears are 100% the same in terms of how hard you will work if there was no friction.

    With a micro drive of 22/11, the friction of the chain is a little bit higher because with the tiny ring and cog the chain tension is increased since the point where the force is transfered is closer to the origin of the crank. The micro-drive approach also has less chain links involved and they are pulling in a tighter arc leading to more friction. Also a very small amount of flex in the chainstay or a sligthly out of round ring or cog will increase the chance of throwing a chain. On a MTB the friction is not really a big concern. Also, for racing wear is not a big issue even in 100 miles. But throwing a chain because it did not have enough wrap is a major pain in the butt and might cost the rider the race.

    A larger drive approach of 40/20 is the same gear as 22/11 but with more links involved and a pulling force that is further from the crank acess the transfer of power along the chain is more efficient and the effect of small amounts of miss alingment is reduced. If the larger drive keeps the rider from throwing a chain in harsh racing conditions it can be a major advantage.

    Larger cogs roll better when the surface is not perfect similar to the way a larger wheel rolls better on bumpy ground. Gerry seems to be pushing it to the logical end game by running a 40 tooth front ring. On many bikes going beyond 40 tooth front ring would give him problems with the chainring hitting the chainstay. I suspect he just started with the 40 and worked backwards to decide what cog he wanted to use.

    Personally I run 36 or 38 tooth rings most of the time. They are plenty big and work well with 22 or 20 tooth chainrings. Combos based on two also work better then odd combos because of the way chain links are designed as pairs of fat/narrow links.

    When racing off road, a gear that is somewhat smaller then a ratio of "2" works well. It sounds like Gerry was running 40/24 for a ratio of 1.66. Many people run bigger ratios but often they are overgearing to the point where they are hurting their performance.
    Last edited by febikes; 05-06-2013 at 03:40 PM.
    Mark Farnsworth, Raleigh, NC
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  12. #12
    1*14*29*2.1 & 1*1*29*2.4
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    had no idea of the physics but Febikes comments seem reasonable. I think the article said something of the sort where it can be a big enough difference to cost a track cyclist a race if he chose the wrong rings. Like Febikes said, it probably means little off road.

  13. #13
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    yep, makes sense to me.
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    Registered pedalphile.

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    So would it really make a difference going from a 32 to a 34 tooth up front?

  16. #16
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    Quote Originally Posted by AnonymouseTech View Post
    So would it really make a difference going from a 32 to a 34 tooth up front?
    BikeCalc.com - Bicycle Gear Ratio Chart

    I've never understood how to calculate gear ratios. Partially because I'm horrible at math. But this takes the guess work out!

    Plug in:

    minimum chainring = 32
    Max = 34

    whatever you like for the cogs. It displays a nice easy to understand chart. Going from 32 to 34 is minimal at best. Seems, as I've known from my limited SS time, that the biggest noticeable difference is in cog size. I've not yet really done much with chainring sizes as you can get a handful of cogs on the cheap till you find what you like.

    That said, I'll be getting a 34t chainring when I finally decide on new cranks.
    SS ==> Nut up or Shut up!

  17. #17
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    Quote Originally Posted by Cormac View Post
    BikeCalc.com - Bicycle Gear Ratio Chart

    I've never understood how to calculate gear ratios. Partially because I'm horrible at math. But this takes the guess work out!

    Plug in:

    minimum chainring = 32
    Max = 34

    whatever you like for the cogs. It displays a nice easy to understand chart. Going from 32 to 34 is minimal at best. Seems, as I've known from my limited SS time, that the biggest noticeable difference is in cog size. I've not yet really done much with chainring sizes as you can get a handful of cogs on the cheap till you find what you like.

    That said, I'll be getting a 34t chainring when I finally decide on new cranks.
    Well no to clarify I already have my gear ratio planned out. Initially the plan is 32x21 but this thread has me thinking of 34x22 for chainwrap purposes. But if the difference in extra teeth doesn't help chainwrap then I'll just keep my front 32t.

  18. #18
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    what I gathered from the link to the surley page a few posts up is that it would add 1 extra tooth worth of engagement. 32t ~ 16t effectively. So 34 should be ~ 17 up front.
    SS ==> Nut up or Shut up!

  19. #19
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    Quote Originally Posted by AnonymouseTech View Post
    Well no to clarify I already have my gear ratio planned out. Initially the plan is 32x21 but this thread has me thinking of 34x22 for chainwrap purposes. But if the difference in extra teeth doesn't help chainwrap then I'll just keep my front 32t.
    If you are buying new ring/cog there is no reason not to go with the bigger combo. The 34/22 combo is also better because both the ring and the cog are even numbered. This means that on a normal chain the fat and narrow links will stay in sync with the teeth such that as the system wears a given tooth valley will always see the same type of link.
    Mark Farnsworth, Raleigh, NC
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