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Cranks for a fixed gear bike?(7 posts)

Cranks for a fixed gear bike?jayb29
Jan 20, 2003 3:06 PM
Hi

I am building my first fixed gear bike, and trying to use parts I have laying around. I have some Race Face cranks (170mm) from an old 'cross bike - can I use them on a fixed gear? Is there something special about cranks for fixies?

Thanks
Jay
re: Cranks for a fixed gear bike?tiken
Jan 20, 2003 4:26 PM
This is my experience with my Surly SteamRoller. I had trouble with toe of shoe-to clips-pedal-front wheel overlap when I used to long of a crank. Also, I got nervous going around corners with longer cranks, a fear of kissing the asphalt with my pedal.
re: Cranks for a fixed gear bike?tiken
Jan 20, 2003 4:34 PM
This is my experience with my Surly SteamRoller. I had trouble with toe of shoe-toe clips-pedal-front wheel overlap when I used too long of a crank. Also, I got nervous going around corners with longer cranks, a fear of kissing the asphalt with my pedal.
Those should work...phlegm
Jan 20, 2003 6:00 PM
I have 170s on my fixie. It is true, the longer your cranks, the more likely you'll strike the ground on a hard turn. I've never hit the level ground with mine, but they're on a mountain bike frame (which has a bit more clearance than a road frame). Short is also good on a fixie because you'll be spinning a lot.
No problem with Chainline?jayb29
Jan 21, 2003 5:45 AM
I think the 170mm length will be okay for me - but is the spacing or anything different on these mountain bike cranks that will not allow for proper chainline?

Thanks
Jay
I think it will workmadstork
Jan 21, 2003 7:32 AM
Go to sheldonbrown.com and find chainline under the glossary. There's a list of typical chainline numbers for Shimano cranks. You'll see that the mtb numbers are different from road. I'll guess that the Race Face number will be close to Shimano mtb. With three chainring positions up front and the ability to move the rear chainline around with spacers, I think you can make this work. Probably the middle chainring will be your best bet.
ChainlineTig
Jan 21, 2003 3:44 PM
A double crank like the one you mentioned will work fine. The bottom bracket will help determine the chainline. I bought a Shimano UN-51 68x110mm square taper bottom bracket in eBay. The 110mm spindle length works fine, but I wish I bought a shorter 107mm from him ("safetycycle") like this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=7295&item=2702359098
Not to change the chain line, but to help place the left crank a little closer inboard.

Once you mount your cranks to a bottom bracket, you can play with the chainline by mounting the chain ring either in the inner position or the outer. You'll need a set of single stack chainring bolts since the original ones are spaced for two rings. The BMX type works, or you can get some from Harris Cyclery. If for some reason you need to push the chainline even closer inboard you can use these 3mm chainring spacers (pictured below):
http://www.sheldonbrown.com/harris/singlespeed.html

Depending on what configuration you are using on your rear wheel's hub (track hub/flip-flop hub/threaded freewheel road hub), you might have to dish the rear wheel and move the axel spacers to keep the wheel centered while retaining a good chainline. I emailed Sheldon Brown when ordering parts and his advice saved me from having to buy the spacers. I bought the WE1220 $119.95 QBP rear wheel with the Suzue basic flip/flop hub and haven't regretted the purchase.