I replaced the factory GY HTs with a set of Cooper A/Ts and ran them for 30K miles and 8 years and just replaced them with Michlein LTX MS2s from COSTCO. They were a good tire and gave me good service and still had good tread, but replaced them because of age from a safety standpoint. Close to 70% of those 30K miles were towing and within 200lbs of the max load on the rears on my Van.
Larry