I replaced my seven year old C rated tires with D rated tires because it gives me more leeway on tire pressure.
At 50 psi my tires are C rated like the old tires, at 65 psi they are D rated. So, if I drop a few lbs of tire pressure I am still within the old tire rating.
This may sound strange but last winter we left the 20 degree weather in Indiana for the 80 and 90 degree weather of OK and the TX panhandle, then back to the 30's in the mountains of NM and AZ. Afterwards it was on to Tucson and down near the Mexico border in 90+ heat then up to the 20 degree mountains of Zion and Bryce in UT. We had to skip Arches because the roads were snow closed. In the 5000 miles of towing the tire pressure varied considerably.
