Tires degrade over time due to the effects of ultraviolet
light, extreme temperatures, high loads, and
environmental conditions. It is recommended that tires
are replaced every six years, or sooner if required, even if
tread depth is above the minimum.
When a tire set becomes worn, replace all
The following information relates to the tire grading system developed by the
National Highway Traffic Safety
Administration (NHTSA), which grades tires by tread wear, traction and
temperature performance. Tires that have
deep tread, and winter tires, are exempt from these marking requirements.