Tuesday, March 4, 2008

Q&A: Drivetrain clunk, bicycle noises

Q: I have a 94 Bianchi with the Shimano 105 group. When I pedal it feels
like there is something loose, kinda like a clunk from both crankarms. I
removed the crankarms and reinstalled them they are tight, the pedals are
tight, I took apart the cassette cluster and cleaned it up. The spindle does
not seem to have any play it. I also took the chain rings off cleaned them
and reinstalled. Still the clunk. The only thing I didn't touch was the
sealed crank bearings because there wasn't any play in the spindle. What do
you think?


A: Hi Al,
I think the bottom bracket cartridge is loose in the frame - the cups aren't
tight enough so it's moving under pressure. I would remove the crankarms
again and using the correct bottom bracket tool, I would first make sure the
right-side (chainring side) cup was nice and tight in the frame (turn
counterclockwise to tighten) and then I would check the right side (turn
clockwise to tighten). Usually, when there's a clunk like this, it's from
the whole BB moving and that should fix it. If you have some blue locktite,
it would be a good idea to put a couple of drops on the threads before
tightening to make sure the cups stay tight, but that's not mandatory.

Hope that helps quiet your bike, and note that I have a huge story on
keeping bikes quiet on my site with a zillion more bicycle noises and how to
shut them up here: http://www.jimlangley.net/wrench/keepitquiet.html

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