Tires

When looking at a tire on a car, light truck or trailer, there’s a lot of information on that tire besides the brand and name of the tire. All the letters and number mean something specific about that tire. After reading this blog you should have a better understanding of some of the letters and numbers on a tire.

First we will begin with the size of a tire. The tire size is usually in bigger print than the rest of the letters and numbers. Take tire size P225/50R16 91S for example:

The P means that the tire is a “P-metric” size that was intended for a passenger vehicle. Passenger vehicles are classified as cars, mini vans, sport utility vehicles and light trucks, like ¼ and ½ ton trucks. The P-metric size tires started in the 1970s and are the most commonly used tire today.

If there is no letter in front of the three-digit numeric portion of a tire size, for example 225/50R16 91S, it means that the tire is a “Metric” size, also known as “Euro-Metric”. Euro-Metric sizes originated in Europe. These sizes have the same dimension as P-metric sizes, but P-metric sizes tend to handle more weight.

The “T” in T125/90D16 98M means that the tire is a Temporary Spare, also known as space saver or mini spare. Temporary Spare was designed to be temporarily used only until a flat tire can be repaired or replaced.

The “LT” in LT245/75R16 means that the tire is Light Truck-metric size. LT tires are designed to use on vehicles that are capable of carrying heavy cargo or towing large cargo. Three-quarter or one ton full-size pickups usually have light truck tires on them, as well as some big SUVs and full-size vans. Tires that are marked with the "LT" label are the "little brothers" of 18-wheel tractor-trailer tires and are designed to provide large capacity to accept the additional stresses of carrying heavy cargo.

If a tire size ends in “LT”, 7.50R16LT, that means the tire is a earlier “Numeric”, “Wide Base” or “Floatation”. For carrying or towing heavy cargo loads, these are called Numeric sizes. For 16.5-inch diameter or wider are known as Wide Base sizes. Flotation sizes are used to keep control of a vehicle on loose dirt or sandy surfaces. These tires can be found on three-quarter or one ton full-size pickups, big SUVs and full-vans.

In 195/70R15C, the “C” means Commercial tire. Commercial tires are used on full-size vans and delivery trucks that are capable of hauling heavy loads. In addition to being branded with the "C" in their size, these tires are also branded with their appropriate Service Description and "Load Range" (Load Range B, Load Range C or Load Range D). Load Range is the strength of the tire and ability to hold air pressure. Load Ranges are identified by the alphabet, in ascending order. “F” is the highest rating

The “ST” in ST225/75R15 means the tire is a Special Trailer Service size. This tire is used for boat, car and utility trailers. ST-sized tires should never be used on cars, vans or light trucks.