Originally Posted by
randyjawa
No one here has mentioned that, a few miles after riding, torque the spindle bolts again. In variably, I seem to get a bit more torque on the spindle bolts. Loctite on the spindle bolt threads is a good idea, however; I have never had to do this. Proper installation, maintenance and understanding will, usually, keep your cranks tight. While at it, take the time to check the ring bolts, ensuring that they are still tight.
For installation of the crank onto the spindle taper, I start by ensuring that the female fit is clean and burr free. I take fine emery cloth and attempt to round or bevel each of the four leading edges of the spindle. Doing this will dramatically reduce the chance of pushing aluminum out of place while driving the crank arm up the taper. A wee bit of light oil, on the tapers of the spindle will also be beneficial. I use 3 in 1 electrician's oil and only a very small amount.
But don't keep torquing them. Once is OK. You can always torque them down tighter, but if you do, the time will come when the crank will simply break from a crack radiating out from a corner of the square taper. When you ride a properly tightened crank, as you apply pressure to the pedal, you leverage the crank slightly further onto the spindle, away from the bolt head. So you can always retighten the bolt back to the original torque. If you do this, next time you ride, the crank does the same small move inboard. If you tighten it again, eventually you will have forced the crank so far up the wider portion of the spindle taper that it has no choice but to break to relieve the stress.
This is a case where too much attention is a killer.
Ben