In article ,
TJ Poseno wrote:
I was trying to get my crank arms off today, and they didnt seem to
agree with coming off. So what i did is loosen both of the bolts hold
on the crank arms, then went off and rode the bike in the driveway to
get them loosened, I also put the pedals parallel with the ground and
kinda of stood on them and stomped, trying to put the pressure in the
opposite direction it usually is. I got the left one off in no time
and the right came a little later. It seemed to work great for me,
since i have no crank puller.

As long as your cranks stay tight afterwards there's nothing wrong
with it. But if you mash the flats in the crank arm (because the
spindle is so much harder than the crank arm) they will begin to
loosen even with the bolts installed. If that happens you'll know
you rode it loose too long and you can either put a piece of a coke
can on the spindle and hope for the best or put the crank arm in
the recycle bin.

Think of it like turning a tight steel bolt with a long handled
wrench made out of aluminum, and pushing with all your weight on
it - if the fit is perfect (bolt installed, nothing damaged) then
you can push pretty damn hard on it. But if the fit is sloppy the
wrench is going to be trashed. Most of us have seen this happen
with a forged and hardened steel open-end wrench; doing it to an
aluminum part is a bad joke by comparison.

--Paul