Our captain’s crank arm does not stay tight on the spindle. The bolt backs out after a few miles regardless of tightening torque. It is an FSA SL-K crank with a hollow spindle on a 2005 Speedster. The BB says 24mm. A mechanic told me this problem is due to wear on the splined connection between the crank and spindle. He made a temporary fix using razor blade strips as shims inserted into the splines, which solved the problem for now but does not allow for disassembly/assembly for packing into travel cases.

Im wondering if anyone else has encountered this problem and found a better fix. Or if I have to replace the cranks, if anyone has a recommendation for a replacement. Thanks in advance for any advice.

DubT, thanks for the offer. As it turns out, I decided to contact Comotion today to see if they could help, and by an amazing stroke of luck they have an identical NOS crankset that they are sending to me at a reasonable cost. Looks like my problem is solved.

I may be wrong, but thought that when I spoke to FSA regarding parts for our tandem cranks, they indicated the Gossamers were to have A certain grade of Loctie applied to the clean splines to prevent crank arm loosening.

When I contacted FSA, the advice given was to grease the splines, apply blue Loctite to the threads of the bolt, and use a wave spring washer which should compress half way when the bolt is at the torque written on the bolt head. It could be that using a wave washer and Loctite might have kept my old cranks from loosening, but I went ahead and installed the replacement cranks from Co-motion instead.