Do any of you have an issue with the Left crank arm loosening during rides? I have followed the maintenance guide and tightened the crank arm bolt to where there is no play and then tightened the pinch bolts to the required torque alternating each pinch bolt successively. I get about 2 rides sometimes only one and the crank arm is loose again.
Are you insuring that both mating surfaces on the crank arm and crank shaft are both spotlessly clean and dry?
I have found (7 years working in a bike shop) that ,usually, once a crank has been pedaled when loose, the mating surfaces between the arm and spindle get distorted enough such that it will keep coming loose despite being properly torqued. The only fix is a new arm and possibly a new spindle, depending on the type. e.g. Square taper usually just needs a new arm as the spindle is hard steel and it’s the socket in the arm that gets distorted.
Yes, I had issues with my first left crankarm, was replaced under warranty without any hassle. The original crank pinch bolts were actually bent. I got the replacement, installed per the directions/specs. That stayed tight only a few rides, got loose again. I reset it yet again to specs.
Since that time, July of 2022, I have made no more adjustments and it has stayed tight. I’m confident the original left arm bolts were either defective or possibly the arm itself not even drilled correctly, causing the bent bolts and loosening crank.
But why it took about 3 times to get it to hold, when it was torqued to spec every time, I don’t know.
IMPORTANT TO NOTE, however, that the MAINTENANCE GUIDE for the KICKR BIKE says to CHECK CRANKARM BOLT TIGHTNESS EVERY 96 hours or 4x A YEAR.
I’m sure this need varies according to how big, strong, and violent you are on the bike.
I would check pinch bolts for straight-ness (roll them around on a flat surface and see if the roll true or wobbly) and then be sure to torque everything to spec:
(3.5Nm for center, preload/tensioning bolt, 15Nm for pinch bolts.)
Here’s a link to a long answer I wrote on another thread.