Beau388
Senior Member
Tires heat because of tire flex. You can check the by stretching a rubber band repeatedly, The tire is flat where it touches the pavement and round every were else. Well that is not strictly true. Depending on internal air pressure and tire design, the tire will develop a secondary, rebound flex wave about 20 degrees after the tire looses contact with pavement 40 to 100 mph. (That is why 12 inch trailer wear out in about 2,000 miles at speed of 60 mph). The temperature of the pavement also figures in to the pressure gain; as does, the atmospheric temperature and the sun shine. But, the primary factors are: tire diameter, weight on the tire and air pressure. These factors determine the amount of tire flex and the frequency.
Thus, there is no pressure gain statistics; only empirical knowledge. Tire manufactures specify max cold inflation pressure, max speed; as well as: tread wear, traction and temperature grades. So asking what is normal tire pressure gain unless someone has a coach identical to yours with the same tires driving the same speeds in the same conditions.
For me, with 18,000 lb coach, shod with 6 Sumitomo ST719 tires, cold pressure of 75 psi on the front and 90 psi on the rear: on a 100 degree sunny day, on a black pavement: 89 psi on the front, inside duals 115 psi and outside duals 110 psi. Front axle is carrying 5,040 lbs and the rear 11,880 lbs towing 3,100 lbs with the towed tire pressure at the max cold pressure (50 psi on the dolly and 44 psi on the truck's rear).
Thus, there is no pressure gain statistics; only empirical knowledge. Tire manufactures specify max cold inflation pressure, max speed; as well as: tread wear, traction and temperature grades. So asking what is normal tire pressure gain unless someone has a coach identical to yours with the same tires driving the same speeds in the same conditions.
For me, with 18,000 lb coach, shod with 6 Sumitomo ST719 tires, cold pressure of 75 psi on the front and 90 psi on the rear: on a 100 degree sunny day, on a black pavement: 89 psi on the front, inside duals 115 psi and outside duals 110 psi. Front axle is carrying 5,040 lbs and the rear 11,880 lbs towing 3,100 lbs with the towed tire pressure at the max cold pressure (50 psi on the dolly and 44 psi on the truck's rear).