'Special Trailer' (ST) tires have been constructed for better high speed durability and bruise resistance under heavy loads. Trailer tire construction varies substantially from automotive tires, therefore it is essential to choose the correct tire for your towing application. In general, trailer tires have the same load range (or ply) from bead to bead and are bias ply construction. This allows for a stiffer side wall which provides safer towing by helping to reduce trailer sway problems. The use of 'Passenger Car' (P) or 'Light Truck (LT) tires a on a trailer is not recommended because their construction, usually radial or bias belted, allows for more flexible side walls. This could lead to increased trailer sway and loss of control.