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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 10-06-10, 01:19 PM   #1
CarLo
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shimano plastic BB cup cracked wtef?!

what should I do? get a replacement? return it? I bought it 5 days ago and it recently cracked. i knew that was going to happen.
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Old 10-06-10, 01:33 PM   #2
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wtef is spelled wtf. If a plastic bb cup cracks, it is a sign that the bicycle frame is faulty. The only thing you can do is purchase a new bike.
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Old 10-06-10, 01:44 PM   #3
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the left side and the rest of cartridge shimano BB's are steel , there are aluminum replacements for the right side.
aftermarket.
But really It just stabilizes the sleeve of the assembly..
perhaps you overtightened it when you put it in.?
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Old 10-06-10, 02:13 PM   #4
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Did you put Loctite on it by chance?
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Old 10-06-10, 02:41 PM   #5
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the preponderance of plastic BB cups makes me queasy. Here're some musings on the subject:

-Get an all-metal BB set next time. Some of em are dirt-cheap. All the new shimano square taper BB sets seem to be plastic on the left side, which is sad.
-make sure you don't overtighten or cross-thread the bb cup, regardless of material
-someone mentioned loctite. This stuff could end up effing with the plastic.
-if you're BB is exceedingly difficult to install, you may want to get the shell re-tapped.

-rob
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Old 10-06-10, 03:14 PM   #6
rogerstg
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It was overtightened when installed. It should not be a problem even if cracked if it stays firmly in the bottom bracket. It functions as a round shim/support on the left side. Shimano used to make an aluminium replacement, but I have not been able to find those for some time.
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Old 10-06-10, 03:17 PM   #7
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I've run Shimano's plastic cup for three winters, hasn't cracked yet, sounds like it was overtightened.
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Old 10-06-10, 04:34 PM   #8
CarLo
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that maybe the case. Should I just return it and stick with loose BB? I like it better because it gives you peice of mind that its full metal. Or should I go with the superior design of seal cartridge? i already asked for a new cup and i'll see if i can install this one correctly.
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Old 10-06-10, 04:42 PM   #9
JiveTurkey
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It'll work just fine if it is cracked.
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Old 10-06-10, 11:45 PM   #10
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Got one for you

Quote:
Originally Posted by CarLo View Post
what should I do? get a replacement? return it? I bought it 5 days ago and it recently cracked. i knew that was going to happen.
PM me with your address and I'll send you a NOS alloy replacement. Not sure on the absolute standards, but it's 21.5 mm long and about 34.7 mm outside diameter.
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File Type: jpg alloy ring..jpg (85.3 KB, 7 views)
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