Play in FSA Carbon Crank/MEGAEXO External BB
I recently noticed my chain falling off of the middle ring when under high torque. This never happened before. When I got home I took a closer look, and noticed my entire crank had some play on the chain side. I figure my bottom bracket needs to be tightened, because my bike is only a few months old with about 800 miles, so surely can't be worn out already.
The bike is a Motobecane Century Pro road bike with a FSA Team Issue Carbon Triple 53/39/30T crank with MEGAEXO External Bearing Bottom Bracket. It seems the crank pullers and BB tools I have are shimano and don't fit this beast.
First question: Is this BB adjustable? The play seems to be only on the chain side. It is defintely not the the spider that is loose.
Second Question: Can someone please point me to a procedure for adjusting my BB, or to an exploded view of an external bearning BB. How is an external bearing BB different from a cartridge style BB.
Third Question: Can someone recommend a source for the proper tools to fix this problem.
Fourth Question: Should I toss this FSA crank and BB for something better.
Go to this page: http://road.fullspeedahead.com/fly.a...=tech&taxid=74
Note that there are two Team Issue variants. If you open the .PDF files, they've got the exploded views and assembly instructions. One uses a wave washer between the left crankarm and the bottom bracket, the other doesn't. They're not adjustable in the usual sense.
Whichever variant you have, the place to start is to make sure all the parts shown are actually present, including the slim little blue O-rings that go on the crank spindle. Also, ensure that the bottom bracket's bearing cups aren't loose in the frame, which can be done with the Park Tool BBT-19 and a ratchet or breaker bar.
If you find that it was just a loose bearing cup, then tighten it properly, reinstall the crank (making sure to get all the parts in their proper places), and see how it goes now. Note that you are supposed to use a specific type of LockTite (see the .PDF files). If there were parts missing, they can be ordered via your local bike shop, who can get them from Quality Bicycle Products.
If you want to bag it and get something else, Shimano has their act together a little better IMHO. If your bike is a 3x10 then the Shimano 105 would be a contender.
Oh, and bigger picture: if your chain falls off the middle ring under high torque, also inspect the middle chainring very closely for bent, gouged or nicked teeth.
Last edited by mechBgon; 11-10-08 at 07:39 PM.
Thanks for the good information and link.
From that exploded view, I could see how there might be some back and forth play from a missing part, but not up and down play like I am seeing. I can't imagine the BB has failed already, but it does seem to be the only explanation.
I tried to pull the crank, but it doesn't want to budge, since it is all LockTited together. What do you use to loosen up the LockTite without hurting the carbon fiber?