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Technical FAQ: Mystery crank noises

Originally published: August 18, 2009

Question: I’m sure that you get asked more questions about the stupid noises that drive cyclists up the wall, but please bear with me as you are my last hope. I have a 2008 Specialized Tarmac Pro with a FACT carbon crank and an oversize bottom bracket (which is where the noise seems emanate from). I have taken it to two local trusted mechanics that say the bottom bracket is fine and have no idea what is causing the noise.

It is a solid click/tap every revolution of the crank and doesn’t start until about 20 miles into a ride. It then gets progressively louder and more noticeable under load. Any suggestions/ideas?

-
Geoff

From Nic Sims at Specialized Bicycle:

There are a couple of things.
1. This may sound strange but a lot of the time with bikes with removable hangers if they are loose a small amount the torque of pedaling can be enough to make it move slightly and the sound travels down the chainstays and out the bottom bracket and people think that it is the crank and bottom bracket. So I would try first of all removing the hanger and clean the frame surface and the hanger and then put some grease on both and bolt it back together and see if the noise goes.
2. If the above does not cure it the next easy test is to just check the chainring bolts
3. Lastly I would have the store remove the cranks and make sure that the spider is tight and that there is plenty of grease around the bearings as they are inserted into the frame and that there is grease on the surfaces of the center join.
Those are the most common areas to look at.

-Nic