A quick and accurate check to find an axle bent enough to be noticeable is to pull the wheel, make sure the drum is seated tight to the axle flange, pick a spot on the backing plate to watch the gap between it and the drum, spin the axle and look for any deviation in the gap, (wobble of the drum). How much is too much? I don't have a number, but it should run true without any noticeable wobble. Spend seven years in a body shop and you will see lots of bent axles.
John
