Understanding your tyre size

The series of numbers and letters that make up the size of your tyre can be broken down to give the exact tyre specification.

For example, 26540R1796Y means the following :

WIDTH OF THE TYRE
265 – the first three numbers are the width of the tyre in millimetres

TYRE PROFILE
40 – the next two numbers provide us with the information about the tyre’s height. It is calculated as a percentage – this tyre is 40% of 265mm – or 106mm high. The technical term for this is “the aspect ratio of the tyre”. The smaller the aspect , the lower the profile of the tyre, and this makes the car look sportier.

TYRE CONSTRUCTION
R – the letter in the middle states the way the wires inside the tyre have been constructed. Most tyres sold in the UK are of radial construction and have the letter R

TYRE DIAMETER
17 – this is the diameter of the tyre’s inner rim – it is expressed in inches

LOAD CAPACITY
96 – the load capacity is taken from an index scale. In this instance 96 means that the tyre has a maximum load capacity (including weight of car / passengers / luggage etc) of 710kg

MAXIMUM SPEED
Y – each letter represents a maximum speed the tyre should be driven at.

Speed Ratings

The last letter at the end of the tyre size is the speed symbol. This represents the maximum speed that the tyre should be driven at. These speeds are as follows:
Speed Symbol

Speed (mph)
Q - 100mph
R - 105mph
S - 113mph
T - 118mph
H - 130mph
V - 150mph
W - 168mph
Y - 186mph