Tyre Designations

If you check out the sides of any tyre, you find an alphanumeric code that may look like this: 205/55R16 88V. Each letter and number conveys important information, like whether a particular tyre will be compatible with your vehicle.

High performance Tyres:

Some size designations are preceded by a letter indicating what type of vehicle the tyre is intended for. "P," which stands for "passenger," is the most common. "LT," which stands for "light truck," is also common.

The first number (205 in this example) is a three-digit number which refers to the overall width of the tyre, in millimeters.

The second number (55) refers to the aspect ratio, which is the relationship between the tyre's height and it's width. In this example, the sidewall's height is about 55% of the tyre's width.

The letter following the aspect ratio is usually an "R," standing for "radial."

The next number indicates the diameter of the wheel rim on which the tyre will fit (16 inches, in this example).

The final number and letter represent the service description, or load index and speed rating. The load index is an assigned number ranging from 0 to 279 that corresponds with the load carrying capacity of the tyre; that is, how much weight it is certified to carry at maximum inflation pressure. The rating can be matched against a load index chart to determine corresponding maximum weights. A load index rating of 88 indicates a maximum load of 560 kg.

The speed rating is a letter which indicates the range of speeds at which a tyre is certified to carry a load (see the speed symbols chart to determine your tyre's maximum speed). Each tyre is assigned a rating from A (lowest) to Z (highest). There is one notable exception: the "H" rating falls out of sequence between "U" and "V," and is used for tyres certified for speeds up to 200 km/h. The Q rating is the lowest commonly used for passenger cars. A "V" -rated tyre is certified up to 240 km/h.

Just to recap. A tyre marked 205/55R16 88V would have a width of 205 millimeters, an aspect ratio of 55, would be a radial tyre sized for a rim with a 16 inch diameter, feature a load index of 88 (capable of carrying a maximum load of 560 kg) and a speed rating of "V" (indicating it is certified up to 240 km/h).

It's important to note that markings do not always appear exactly as they do in this example, as tyres can be certified under a variety of designations.

Inflation Pressure

The level of air in your tyres affects your vehicle's overall performance. Not even the highest quality tyre will perform well if it's not inflated properly. The correct pressure varies from vehicle to vehicle and depends in part upon driver preference. Each vehicle has a recommended inflation pressure, usually found on a placard on the door section, door post, glove door, or fuel door.