Originally Posted by
mechBgon
What I'm referring to by "ramp up abruptly" is the point at which the bolt no longer wants to turn because the crank is fully seated at the far end of the splines, and there's nowhere further to push the crank to. Not the initial soft swedging where the crank is obviously (to us, anyway) being pressed further and further onto the splines. Shimano also has made certain square-taper cranksets that were designed to bottom the crank arm onto a collar on the spindle, and it's the same story: tighten until full seating occurs, then stop.
I have only done mine but my understanding is when new the shape of the "bottom" part of the axle spline and that of the cranks is not the same. The crank is intended to form to the axle as part of the initial tightening process thereby creating a zero clearance fit. This only happens on the initial installation and results in a sort of squishy ramping up of the torque over a half a turn or more. When it first bottoms out it feels quite tight but still needs to be tightened quite a bit more to finish the process. Any time after that, when they are removed and reassembled you will get that bottoming out and then a fast ramp up in torque as you describe. When I put my new one on, it got so tight I could barely turn it with my short ratchet, when I put my torque wrench on it, it went another half to full turn before it reached the spec. Use a torque wrench and you will be fine. I don't recommend putting brand new ones on by feel.