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How to read your tyre markings

Noticed some numbers and letters on the side of your wheel? Finding what each number means can be confusing, but it is essential to know what these markings mean when you are looking for the next set of replacement tyres.

Discover the placement of each marking and how this impacts your wheel, and get to know your car better.

Each segment of the number/letter combination represents a different aspect of the tyre.

Here is an image of a tyre sidewall marking “195 / 65 R 15 79T”

Tyre width

The first set of numbers on the marking will be  width of the tyre in millimetres. So in this instance, the tyre with would be 195mm.

Aspect ratio

The next set of numbers after the dash refers to the thickness of the tyre wall, also known as the aspect ratio. This number is recorded as a percentage, so in this case, 65 would have an equal height to 65% of the tyre’s width. Also known as the tyre profile.

Construction

Next, you will see a random letter, such as “R”. This represents the tyre’s construction. R stands for “Radial” and almost all tyres manufactured today will be radial tyres, which are chosen as they are more flexible and comfortable. You could also have “B” for Bias-Ply or “D” for Diagonal construction.

Diameter

The set of numbers after the tyre contraction letter represents the inner diameter of the tyre rim in inches. For example, this tyre has a tyre inner diameter of 15 inches.

Maximum weight

The last set of numbers will indicate the load rating, which is the maximum amount of kilograms that the tyre can carry, as long as the tyre is inflated correctly. So 79 kg max weight.

Speed rating

The final letter, “T” is the maximum speed that a tyre can handle whilst correctly inflated with load. The latter will correlate to the mileage shown on this graph, so this tyre would be 118mph.

LetterMPH
Q100
R106
S112
T118
U124
H130
V149
Z149+
W168
(W)168+
Y186
(Y)(186)

What do the other letters mean?

Date of manufacture

You’ll also find another number on your tyre sidewall which is the date your tyre was manufactured! There will be a four digit number, with the first two referring to the week your tyre was manufactured, and the last two referring to the year. 

Reinforced tyres

Reinforced tyres  are made to handle extra weight. These tyres will be marked to indicate that they have been reinforced, although the marking varies.

This may be shown as XL, EXL, RF, REINF or RFD.

Run flat tyres

With run flat tyres, you can drive for a short amount of time if you lose pressure or have a puncture, giving you the chance to drive to a safe place. The markings to indicate that your tyres are run flat tyres can vary, but will often be shown as ROF, EMT, RFT, ZP, SSR or DSST.

Got a problem with your tyres? Don’t hesitate to contact Smart Wheel Repair for quick and easy repair services based in Aylesford.

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