It's a cold winter morning, the temperature dropped below zero, you come in to your garage and want to check the tire pressure on your car.

You can read the right inflation pressure on a tire placard, which is usually located on a car door edge but also may be on a door jam, glove box door or inside a trunk lid. The tire placard shows the vehicle manufacturer's recommended tire pressure, in this case, let’s assume it is 2.0 bar (29 psi). You check the pressure and it is about 1.8 bar (26psi), lower than the recommended pressure. Then, you inflate the tire on 2.0 bar. Is it the right pressure? Unfortunately not!

Tire pressure check in a garage

Tyres as the only part of the vehicle that is in contact with the ground perform a very important function of carrying the load. Compressed air fills the tyre and carries the overall vehicle weight. Therefore, it is very important to maintain correct tyre pressure.

Tyres are porous and naturally lose air even when they are not being used. Tyres should be neither underinflated nor overinflated but inflated to manufacturers recommended pressure.

tyre pressure effect on tread wear and tyre tracks comparison

Tire speed rating (speed symbol) and load index are very important factors that determine tire performance. The common name for the load index and speed symbol is "service description".

The tire load index and speed rating for light truck tires have some specificity compared to the passenger car tires.

Light truck tire - Tire speed rating and Load index

The term "Light Truck" covers great variety of vehicles, such as vans, SUV's and light duty pickup trucks. This is one of the reasons why the tires are labeled in many ways. It is also important to know what sizing system is applied in a tire designation.

There are several sizing systems for the light truck tire designations currently in use:

Before we begin to discuss about the tire sidewall informations it's important to know standard which was used for designation.

light truck tire size designation and service description

1 - MAX. LOAD SINGLE 1549 kg (3415 lbs) AT 550kPa (80 psi) MAX. PRESS. COLD

2 - MAX. LOAD DUAL 1399 kg (3085 lbs) AT 550kPa (80 psi) MAX. PRESS. COLD