Special Trailer Service tires are developed specifically for use on travel trailers, pop-up campers, boat trailers and fifth wheel trailers. Power King Towmax STR II tires are designed to deliver dependable and long-lasting, on-highway service for towable trailers.Special purpose trailer tires are not intended to be used on cars or light trucks.Towmax STR II tires feature an energy-efficient, lower rolling resistance tread compound to enhance the towing vehicle's fuel economy. This compound is molded into a symmetric tread design featuring a solid center rib, interlocking intermediate ribs and linked shoulder blocks to provide constant rubber-to-road contact to enhance highway stability, traction and wear.The tire's internal structure features twin steel belts (Load Range D & Load Range E-sized tires are reinforced with a nylon cap ply that further stabilizes the tread to increase durability). The Towmax STR II's rounded profile and polyester cord body are designed to help smooth out the trailer's ride.Towmax STR II tires have a Service Description that confirms each size earns an L speed rating. Therefore, running the standard cold tire pressure recommended for the trailer and its load requires no additional adjustment in pressure for speeds up to the tire's 75 mph (120 km/h) maximum speed rating.Special purpose trailer tires are not UTQG rated.