Originally Posted by
gyozadude
But I've personally never damaged a left crank arm due to improper installation or letting it get loose. It simply doesn't happen when properly installed. Certainly, we've had many issues in the past with European bikes with ISO taper getting replaced by JIS spindles and because there was less metal on the left side crank, the looseness and deformation that led to failure would happen primarily on the left. But if properly installed, it's never been an issue of the left crank arm requiring a left-threaded fixing bolt or nut. I've simply never had one come loose and warp if properly installed.
Hi,
See my above post regarding most of your post.
Yes. The left crank doesn't need a reverse thread because properly
installed there is no precession applied to the nut/bolt holding it.
Once things get loose and chewed up a bit that is no longer true.
Tightening the nut/bolt can't make the crank seat properly and
it will come loose quite (or very) quickly due to the precession.
The damaged crank taper ridges need to be filed back to flat
for it to seat properly and solidly on the BB square taper.
rgds, sreten.