What the text and numbers on tyres mean?

Tyre Code Meanings:

The numbers and letters on the side of your tyre are known as the tyre code, and they indicate the size, profile and load/speed ratings of your tyre. The tyre code is made up of seven different elements, which represent, in order, passenger car type (p), the section width (225), aspect ratio (45), construction (R), rim diameter (19), load index (92) and speed rating (W).

Passenger car type:

P = Passenger Car

T = Temporary Spare

LT = Light Truck

C = Commercial

ST = Special Trailer Service

SUV and 4×4 type:

SUV = Sport Utility Vehicle

MT = Mud Terrain

AT = All Terrain


The width of your tyre is measured in millimeters (mm) and is the first number listed on the side of your tyre. The width of your tyres affects the amount of contact they have with the road, which in turn affects traction, handling and fuel economy.

Aspect ratio:

The aspect ratio is the second number listed on the side of your tyre and is a percentage of the width. This number indicates the height of your tyre’s sidewall as a percentage of the width. A low aspect ratio (30 or less) results in a tyre with a shorter sidewall and a wider tread, while a high aspect ratio (70 or above) results in a taller sidewall and narrower tread.


The construction of your tyre is indicated by a letter following the aspect ratio. “R” indicates a radial tyre, while “D” indicates a diagonal (bias ply) tyre. Radial tyres are the most common type of construction found on passenger cars and light trucks today. Diagonal tyres are less common, but can still be found on some older vehicles.

Rim Diameter:

The rim diameter is measured in inches and is the third number listed on the side of your tyre. This number indicates the size of wheel that your tyre is designed to fit.

Load Index:

The load index and speed rating are two of the most important elements of the tyre code, as they provide information about the maximum weight and speed that the tyre can safely carry. The load index is expressed as a number. The load index is a numeric code listed after the rim diameter and before the speed rating. This number corresponds to the maximum weight that your tyre can support whether it’s a large truck or a small UTE when inflated to its proper pressure. The higher the load index, the greater the weight capacity.

Speed Rating:

The speed rating is the final code listed on the side of your tyre and indicates the maximum speed that your tyre can safely achieve. Speed ratings are represented by a letter code, with “S” being the lowest and “Y” being the highest. It’s important to make sure that you choose tyres with a suitable speed rating for your vehicle, as using tyres with a lower rating than recommended could result in overloading and excessive wear.

If you’re not sure how to interpret the tyre code, or you’re not sure which tyres are right for your vehicle, you can always ask a qualified tyre specialist for help. Here at Double D Tyres we will be able to advise you on the best tyres for your vehicle whether it’s a car, truck, semi-trailer, van or Utes.

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