[cpecrivaine]

So I've got a 2011 Cervelo R3 with SRAM cranks and the right crank arm keeps working its way loose. I've retightened it a few times, and thought it might be fixed but it loosened yet again. So I'm figuring there's a better solution than just throwing an Allen key in and snugging it up for the third time. Since I'm an amateur wrencher, I'll probably take it to my LBS, but I wanted to get some ideas first as to what's going on--and why I'm too dumb to fix it.

 

[RoadrunnerLXXI]

Did you make sure the crank shaft is flush with the seal bearing cartridge? What about the the arm on the other side is flush with the cartridge? I would use some loctite before I re-tighten it a third time.