UNDERSTANDING DOT TIRE INFLATION PRESSURES AND LOAD CAPACITY
This document includes information regarding proper inflation pressures for Highway use of DOT tires.
TIRE SIDEWALL INFORMATION
Federal regulations mandate that tire manufactures place permanent information on all DOT tires showing maximum load and inflation. The inflation pressure shown is the maximum allowable under any circumstance, and necessary only to provide a safe load carrying capacity of the tire or when sustained high speeds are expected.
PROPER INFLATION PRESSURE
Again, the pressure listed on the tire sidewall is the maximum pressure and not intended as a guide for normal inflation pressure. These things are dictated by the vehicles weight and use (ie: high speed). Always start with the vehicle manufacturer’s information on inflation pressures. With modified vehicles, or vehicles using tire sizes other than OE, it is valuable to understand the weight bias of the vehicle and intended use along with the maximum load capacity and inflation.
Always use a tire with a load carrying capacity that matches or exceeds the weight carrying capacity of the OE tire. With light truck tires and applications, the load capacity is more critical than the load range when choosing non OE sizes. Due to the reduced load capacity on P-metric tires, Dick Cepek does not recommend their use on O.E. LT tire applications.
It is also important not to check tire pressure when the tires are hot after use. Over-inflation can produce a harsh ride, makes the tires susceptible to impact damage, and promotes faster than normal tread wear along with decreased traction performance. Under-inflation (or over-loading) will cause excessive heat build up which can lead to tire failure.