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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 08-04-10, 10:29 PM   #1
sagbuya
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Crank Clearance when bolts are torqued- single speed bike, help appreciated

my friend bought Sugino grand mightys for his urban outfitters singlespeed bike (dont ask me why -_-)
he asked me to install it because i have the tools.

i have a slight problem that could get bigger.
i installed the bottom bracket, i seated the cranks and torqued in the bolts to +/- 25 ft lbs

i rode it around a bit to test it out my work....not so good, the drive side arm was kissing the stay everytime it went up.

i sat down with the bike, cried a bit, then started over.

i double checked the bottom bracket, reinstalled it. reseated the cranks but this time i didnt push the drive crank all the way in with the wrench (so the drive side is not torque +/- 25 ft lbs). and WAH LAH, the crank clears the chainstay.

my question is: Is there anyway for me to torque the crank around 25 ftlbs without pushing it all through the spindle? i need about 1mm or 1.5mm of space for the crank to clear the stay.

thank you for reading, and any help/comments appreciated.
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Old 08-04-10, 10:39 PM   #2
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You should be able to find that size shims for BB's at loosescrews.com or bikeparts.com. Just make sure you have sufficient clearance for the 'shift' on the left crank arm.
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Old 08-04-10, 10:41 PM   #3
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what would the shims do for the BB?


ahh nevermind, now i get it. hmm okay thanks, spacers should help

Last edited by sagbuya; 08-04-10 at 10:45 PM. Reason: NOW I GET IT
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Old 08-04-10, 10:49 PM   #4
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Just make sure you have sufficient clearance for the 'shift' on the left crank arm.
AHH i just checked, the left crank might not clear, any other suggestions?
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Old 08-04-10, 10:56 PM   #5
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Yes, there are a few approaches to take. A spacer under the fixed cup of the BB is one - that'll move the cranks over a little to the right, so be sure you have enough clearance on the left side crank before doing this. A longer spindle would be a second method but requires that you're able to find one of the right length.

Our tandem had a similar problem, but it was on the left side and the crank rubbed on the lockring for the adjustable cup. Eager to get the bike up and running without having to wait for yet another part, I cut a shim out of a soda can and put it around the square taper of the spindle on the NDS. Tightened everything down and that gave sufficient clearance. Admittedly it's not the preferred solution, but it has held up fine for over 30 years and quite a few repackings of the BB bearings. Of course when/if the spindle ever wears out I'll try to replace it with one that's longer on the left side (which isn't completely NDS since the captain's drive power is on that side).
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Old 08-04-10, 11:16 PM   #6
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the problem for is that i can't find a longer spindle for him, for cup and cone BBS
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Old 08-04-10, 11:21 PM   #7
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the problem for is that i can't find a longer spindle for him, for cup and cone BBS
Which was my problem as well. That's why I cut up the Coke can to make a shim that I wrapped most of the way around the square taper of the BB spindle before sliding on the crank.
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Old 08-04-10, 11:33 PM   #8
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i want to try it, but my can cutting skills are lacking.
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Old 08-05-10, 06:52 AM   #9
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If you can't find a longer spindle for the current cup-and-cone bb, consider a Shimano cartridge. The UN-5X series is available in spindles of 122.5 and 127.5 mm.

I had an older Trek MTB that had the same problem and it took the 127.5 mm bb to let both crank arms clear the chainstays.
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Old 08-05-10, 08:34 AM   #10
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+1 Just buy a new cartridge bb. The Shimano UN26 series (that's their bottom line) can be found on line for $10, in many different spindle lengths.
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Old 08-05-10, 02:01 PM   #11
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Quote:
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AHH i just checked, the left crank might not clear, any other suggestions?
A longer axle?

How wide is the bottom bracket shell? Are you perhaps installing a bottom bracket intended for a 68mm shell into a 70mm shell?
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