I bought a set of nnbs helpers that use the firestone sleeve bags. Everything was great always left at least 10-15psi in them at all times. Then the other day I noticed the rear being a little rougher than normal. So out cam the jack stands and I noticed that my helpers were flat! Added air aired have a rub spot in the bag. But can't find anything they rub against. It's on the bottom of the bag where it rolls over its self. Any ideas? Just replace or look futher?