ORIGINAL: jbdismukes
In addition to the above suggestions, add another block inside the OUTER half of the pant, with a hole the diameter of the axel drilled into the block . Center the hole so the axel plugs into it when the pant is secured using one of the above suggestions. This arrangement should eliminate much of the up-and-down flexing of the pant which has been part of your problem.
Jack
Doing this takes almost all the flex out of the wheel pants because they are held in place from both sides which is 99% of the battle.
