Are you asking how much the tire will move during the axle's range of motion? That's easy to test yourself in the driveway with some jackstands and a floor jack. Cycle the axle throw full range of motion and see if any rubbing.

 

No, I mean how much will the tire itself deform when off-road due to being pushed around when aired down (much harder to test for). For instance if at worst-case flexing in the driveway I find a 1" gap, will that rub off-road? Or a half inch?

 

Have you actually experienced any tire rubbing with your setup?

 

I just put it in last weekend, haven't wheeled it yet. It should get within half an inch when flexed and is around 1.375" sitting flat. I'll post up what I find, might try to take it out Sunday.