Copied from Goodyear bulletin PSB #2011-13 dated May 18, 2011
Many trailer manufactures establish the recommended tire inflation pressure based on the 65 mph (104 km/h) rated speed for ST tires. In these cases, the ST tires should be inflated 10 psi (69 kPa) higher than the trailer placard for speeds up to 75 mph (121 km/h) (wheel must be rated for this higher inflation pressure). If the trailer manufacturer’s placard specifically states that the cold inflation pressure is suitable for speeds above 65 mph (104 km/h), no additional inflation pressure adjustment is required.
