Tire Sidewall problems of the 2002 Ford E-350

(1) normal tire rotated every 3000 miles run with 55 lbs. Front 85 lbs. Rear checked weekly (2) side wall on both inside and outside dry rotted to point of air pockets are forming on outside of tires. (3) tires replaced with bridgestone v-steel r265 I went to two different goodyear dealers 1st in ormond beach FL the service manager said that is not a problem it is cosmetic! 2nd goodyear dealer in bridgeville PA agreed the tires were bad and a danger to ride on, and offered a sixty-two dollar discount on new tires (with the discount the goodyear store would have been $242. 00 higher, than sam's club for the same tires without a discount) the two dealers were about eight months apart.