i have 2012 34trse, tire size is ST235/80 R 16 E rateing. i have had 3 tire blow outs on it, 2 tires in a 400 mile trip. before every trip, i cheek tire pressure, i had 75. 5 psi in each tire. on side wall of tire it says 80 psi, is this what caused the blow out? i drive no more than 67 miles a...