New tires on the Silverado

Yesterday while adjusting the drum brakes on the rear of the Silverado I noticed the tires were cracking at the treads. They were Michelin LTX M/S2 which had 25,000 miles on them and were 3 1/2 years old. I expected more from the tires as they were warrantied for 60,000. Took the truck to Costco, they pro-rated them. I paid $303 out of $859 price for new ones. I now have the Michelin LTX M/S Defenders warranty for 6 years and 70,000 miles.

Running Firestone Transforce HT on the crewcab. They are just over 7 yrs old and rears ate getting pretty worn, don't rotate and they run at 70-80 psi most times.

Plan on getting another set.