Singlespeed & Fixed Gear - Using older, spiderless cranks for a fixed gear conversion?

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willgovus
07-21-09, 11:15 PM
I'm currently converting a schwinn le tour 3 which was previously a single speed to a fixed.

The original cranks are the type where the chainring is directly attached to the back/base of the crank arm rather than a spider. The chainring seems to be attached to the crank by a not so sturdy method, which makes me imagine it could become detached rather easily if put under the strain of a fixed gear.

Anyone have any experience using this type of crank for a fixed gear?

Also, I've looked into purchasing new cranks for this very reason but I don't know how to determine whether the spindle/bb would accept JIS or ISO crank arms? The cranks are labeled simply as 'le tour' with 'japan' stamped on the back.

The spindle has a threaded section jutting out of the end of the tapered section rather than being internal, which seems against the norm? I'd prefer not to buy a new bottom bracket if possible considering I'm on a budget and the current one works fine aside.

Any help would be greatly appreciated.


cs1
07-22-09, 02:05 AM
If you're really concerned, I'd go with a different crank. Good luck

REMspeedwagon
07-22-09, 02:31 AM
The BB spindle should accept a JIS square taper, if I am not mistaken.
You can mount a new crank on there no worries, just reuse the 14mm nut.


TimArchy
07-22-09, 06:33 AM
Either use what you've got or get a new crank and BB. Cranks are dsigned to be used with specific BB spindle lengths. Throwing any crank together with any BB sometimes works, but chances are you'll be back at the shop the next day b/c the chainline isn't right. A threaded BB spindle is a very old and cheap method of attaching the crank. What you've got right now is obviously pretty low quality. But that does not mean that it will not work perfectly as a fixed gear crank so long as you are not racing or doing stupid tricks on it.

Anything old that is not from Italy or Spain uses JIS. Anything modern that is not Campagnolo or Miche uses JIS. The exception to go these rules is the Sugino 75 which uses ISO taper.

If you are buying a budget crank, go ahead and get a cheap BB to match it. It'll only cost like $15 extra and you know it will work.