I think I am convinced to go back to 285 or 265 tires. With my 3. 54 gears I am lugging the motor trying to run 55 mph in od 1350 rpm especially while towing with my 315 tires. Running out of od at 55 I am at 1900rpm. I usually pull loads under 5000 lbs but it pulled better with the smaller tires. I have 10-15k to go on these yet. Anyone else gone through this??? Also these speeds are from my gps as the speedometer is obviosly off.