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Fixed Gear Crit => what gear inch?

Old 07-28-07, 10:05 PM
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Fixed Gear Crit => what gear inch?

If you race fixed gear class crits, what gear inch do you recommend?
I am running 70" now at 48 x 18T.

Last edited by MIN; 07-29-07 at 12:35 AM.
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Old 07-28-07, 10:40 PM
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that has to be too small. 48x18 at 110 rpm isn't even 23 mph. 48x16 sounds better to me but maybe even 48x15 would be good. say your typical pedal speed is between 90-110:

48x18
90 - 18.75
100 - 20.84
110 - 22.92

48x15
90 - 22.51
100 - 25.01
110 - 27.51

man, looking at that has me scared. 48x14 is kinda big sounding, but is equivalent to 53x15 which is close to what i run in most crits. i guess it depends on how fast you think the race will go.

don't clip a pedal
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Old 07-28-07, 10:47 PM
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Originally Posted by fly:yes/land:no View Post
that has to be too small. 48x18 at 110 rpm isn't even 23 mph. 48x16 sounds better to me but maybe even 48x15 would be good. say your typical pedal speed is between 90-110:
Thanks - great info.

I am running a commuter cog right now. I need to get a smaller one for crits.
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Old 07-28-07, 11:06 PM
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Technical course = 48x15
Open course = 48x14

btw - my calculator gives different speeds than the post above.
48x15 @ 110 rpms = 28.16mph and 48x14 @ 110 rpms = 30.17mph
48x15 @ 120 rpms = 30.72mph and 48x14 @ 120 rpms = 32.91mph

(chainring x rpms x .08) / cog = mph
use .13 for kph
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Old 07-29-07, 12:06 AM
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Originally Posted by YMCA View Post
Technical course = 48x15
Open course = 48x14

btw - my calculator gives different speeds than the post above.
48x15 @ 110 rpms = 28.16mph and 48x14 @ 110 rpms = 30.17mph
48x15 @ 120 rpms = 30.72mph and 48x14 @ 120 rpms = 32.91mph

(chainring x rpms x .08) / cog = mph
use .13 for kph
i think according to sheldon brown mine is closer. just teasing. i guess ite depends on if he is runing 25c or 23c tires. i ended up spending several minutes setting up the formula on the old ti-85 (which included over an hour of learning how to program the thing), so i can plug in any chainring, any cog, and any rpm and find the speed. then i found the sheldon sight which rendered it pretty much pointless. i believe that an rpm to speed graph will increase linearly, so one can enter the preferred chainring size and different cog options to the sheldon brown sight, ask for speed at 100 rpms and then use that number divided by ten to add or subtract with rpm increases or decreases of 10. for example, sheldon sight says that 48x15 @100 is 25.0. okay, that means that 48x15 @110 is 25 + 2.5. 48x15 @90 is 25 -2.5. 48x15 @ 10 would be 2.5 etc. seems to be the easiest way to get lots of information at relative low brain function, of which i am certainly a fan.
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Old 07-29-07, 12:28 AM
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This is a great fixed gear calculator.

http://software.bareknucklebrigade.com/
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Old 07-29-07, 08:18 AM
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Guess id run similar to what I use for a points or scratch race. Somewhere in the 88" to 92" range depending on who is there. A good starting point would be 49x15 fixed. Have ridden entire training crits in 53x17 for spin work w/o a lot of stress.
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Old 07-29-07, 09:10 AM
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Originally Posted by Voodoo76 View Post
Have ridden entire training crits in 53x17 for spin work w/o a lot of stress.

That's always a good thing to do when the form is good enough. Group rides on 42x15 used to be a staple of mine. 120 rpms was 27mph, so it was no problem to stay there for extended periods, with jams of 130-160 rpms here and there.
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Old 07-29-07, 01:03 PM
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Originally Posted by YMCA View Post
120 rpms was 27mph, so it was no problem to stay there for extended periods, with jams of 130-160 rpms here and there.

AHHHH. my legs would look like willis mcgahee's in the national championship game froma few years ago. the only time my legs are moving that fast, i am going down a hill fixed and am trying to slow down anyway i can. i don't think i can apply any watts when i am spinning that fast on a fixie and i don't think i can even spin that fast on my road bike for more than a few seconds. good for you if you can handle that though.
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Old 07-29-07, 01:04 PM
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Fixed gear crit? Do they force everyone to run a front brake to make it less dangerous? I train and commute brakeless but wouldn't want to be in a peloton with a bunch of other fixed gears if the other riders had brakes on their bikes.
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Old 07-29-07, 02:16 PM
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Depends on the crit. Some of them have rollout limits. 48x16 is a hair under 21 ft. I don't think anyone would race that gearing on Tabor, but Tabor doesn't have a gearing restriction.

But yes, its a spinfest when the first attack goes.
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Old 07-29-07, 03:17 PM
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What's a rollout limit and what GI do you use at Tabor? I was just there today and I can't imagine using a 48*15T there. It's so hilly.
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Old 07-29-07, 04:06 PM
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Rollout is the distance your bike goes on one revolution of the crank. Here's a chart of the most common gearings: http://www.juniorvelo.com/?p=197

I don't ride in the Tabor series, but if I did, I'd probably gear myself around 71" (46x17 for my setup). Some of the guys I know that ride that series go a bit taller.
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Old 07-29-07, 10:05 PM
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Tabor = @ 77-81 GI, at least thats what I was using, placed ok, but Blackwelder(sp?) seems to win with whatever gear he wants .
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