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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 07-02-12, 08:46 AM   #1
Muggle
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What gear ratio will feel the same?

I'm building a fixie. Right now I ride a SS 29er mountain bike geared 33-16. The smaller chain ring on my old road bike's crankset has 39 teeth, so I'm wondering what size sprocket I should run to get a little more power than that.

I'm not sure on the crank size, they seem similar. I'll be running 700c on my fixie. I'm not too concerned with the force it'll take to pedal, my legs will acclimate themselves to that, I just want the same top speed or a little more even.

I've tried looking at gear conversion calculators and searching, but I've had no luck.

Thank you.
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Old 07-02-12, 08:54 AM   #2
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33/16 on a 29er is 59GI.

59GI is pretty low for a road fixed gear. It's generally advised to start around 70-80GI. Perhaps since you're used to low gearing something in the high 60's would be good, such as 44/17, 46/18, 49/19, etc.
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Old 07-02-12, 09:16 AM   #3
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The thing is, unless I want to swap out my whole crankset I'm stuck with using a 39 tooth chain ring to achieve a decently straight chain line. How small of sprockets do they make that are still compatible with track wheels?
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Old 07-02-12, 09:21 AM   #4
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The thing is, unless I want to swap out my whole crankset I'm stuck with using a 39 tooth chain ring to achieve a decently straight chain line. How small of sprockets do they make that are still compatible with track wheels?
39/15 would be a great starter gear. I'm no expert, but I am a beginner, and 69 gear inches is what I run (44/17), and that's what 39/15 works out to.

Last edited by LessonLearned; 07-02-12 at 10:19 AM.
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Old 07-02-12, 09:34 AM   #5
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Great, thanks!
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Old 07-02-12, 09:59 AM   #6
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Sorry, I didn't realize you were converting an old road bike. LessonLearned is right, 39/15 should do the trick.
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Old 07-02-12, 11:49 AM   #7
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Since you're used to a lower gearing, and cogs aren't *that* expensive, it wouldn't hurt to start with a 17T or so, get your knees used to it, then move to smaller cogs as your skills improve.

I used ~60 GI on the road for a while before moving up to 65, then 69, where I'll most likely stay.

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Old 07-02-12, 11:51 AM   #8
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I personally like a higher gear for fixed road riding than for SS trail riding.

MTB = 34x17 on 26x2.1"
Fixed = 43x16 on 700x28c.
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Old 07-03-12, 04:33 PM   #9
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Just check here for exact ratios and info...

http://software.bareknucklebrigade.c...it.applet.html
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Old 07-03-12, 06:07 PM   #10
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When comparing bikes with different wheel diameters, you must compare meters/feet of development. Basically how far you travel per pedal stroke.

A smaller factor in the feel will be the crank length. Longer cranks feel easier given the same meters of development. This is because you have a longer lever with which you are applying torque to the chain.
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Old 07-03-12, 09:37 PM   #11
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dude use sheldonbrown.com/gears it is handy calculator you can plug in numbers for gears you like and compare
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