I just replaced all four on the fifth wheel. We just finished 2200 mile trip and the last day 300 miles i noticed this 10 miles from home (side wall bubble). I always keep air pressure at max and check all tires and lugs each morning before pulling out. The tires are 1 year old and have 8,000 on them, I didn't even hesitate in replacing all of them when i seen this. I replaced with the new Carlisle HD 85 mph rated 80psi.
Tow max did give me $90.00 back on warranty for the one tire. I should have taken a blow torch to the other three
