Wornout Crankarm?



dhk2

Active Member
Aug 8, 2006
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I've noticed a ticking/creaking sound on climbing on the last few rides. Today in the garage I put the front wheel up to the wall, and found that the ticking/creaking appears to be coming from the left crankarm when it's loaded and unloaded by putting weight on the pedal. I suspect the crankarm because I can feel the click when touching the arm. It's not the pedal, as I pulled it off and can still make the noise by stepping on the end of the arm.
 
Removing, regreasing and re-torquing the crankarm to 30 ft-lbs didn't change anything. When reinstalling the arm, I did notice that the arm now appears to "bottom" on the spindle, ie, it seems to press further than when the cranks were new (at the same torque).
 
The crank is an FSA Team Carbon Pro, running on a Ti ISIS spindle. I changed the alloy bolts to steel years ago. The crankset has almost 28K miles on it now. The arms have been removed and re-installed at least once a year since I got the bike in early 2004. There is no sign of galling or obvious wear on the alloy crankarm mating surface; I've always used anti-sieze or grease when reinstalling.
 
I'm guessing now that maybe the alloy end of the crank has "yielded", or stretched out so that the tapered interference fit no longer clamps up properly to the ISIS spindle. It has been 7 seasons and 28K miles now, with lots of hills,..is it time for a new crank?
 
 

alfeng

Well-Known Member
Jul 23, 2005
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Have you considered the possibility that you may need to replace the BB?
 
If you think the problem is with the "taper" on the splines ... or, to eliminate it as a possibility ... then, cut a small (probably about 5mm x 3mm) rectangle from a soda/beer can use it to "shroud" one spline & thereby eliminate any "slack" in the ISIS interface ...
 
If the problem is gone after shimming the spline, then it's gone!
 
If it feels the same as before, then the problem is probably the BB.
 

dhk2

Active Member
Aug 8, 2006
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Alfeng, thanks for reply. I found the ISIS spec and drawings online yesterday after I posted. The specs advise that a proper fit will allow the crankarm to be pressed onto the tapered splines by hand within roughly 5 mm from the inside stop. Mine appears to meet this requirement, so time to look elsewhere.
 
Now I'm thinking the tick may be in the crankarm itself, as I can distinctly feel it when touching the arm (making the noise by standing/releasing weight on the pedal). Like most "CF" cranks, the FSA is a "composite" arm, meaning an alloy core with a CF overwrap. Believe it's possible that the arm has debonded internally with age.
 
Anyway, what I plan to do next is find an ISIS crankarm I can substitute as a test. If the tick disappears, it will be time to buy a new crankset......or at least a crankarm.
 
BTW, my bike has a Megatech BB, which uses OS (43mm) cartridge bearings pressed directly into the BB shell. I changed the bearings last fall; the press-fit is tight and the bearings still feel pretty good. In my experience, crunchy bearings don't produce a "static" tick like this. (Happens once when the weight is applied, then again when weight is removed).
 
When I've had this kind of tick/click in the past, it's been from seattube, bottle cages, rear stays, handlebar/stem,....places where a tiny relative motion occurs when weigh is applied from one pedal to the other in static mode.