Decoding Tyre Size Markings

205/65 R16 80T

The above is a typical tyre size code found on the tyre sidewall. When replacing tyres on your car, trailer or caravan it's important that you understand these codes to ensure that the bargain tyres you're being offered really are any use to you.

205/65

The first group of digits, '205/65' in the example, specifies the tread width and what is referred to as the aspect ratio of the tyre. The '205' is the tread width in millimeters. This dimension is related to the width of the wheel rim it is to be fitted to. Most rims will accomodate a tread width one size larger or smaller than the tyre it was fitted with when new should you be struggling to find a tyre to fit an older vehicle but allways seek advice from a tyre supplier.

The '65' refers to the aspect ratio of the tyre which is just a technical way of referring to the width of the tread divided by the height of the wall. Most caravan or trailer tyres are likely to be around 70 or 80 with anything much less than the 65 of the example being aimed at the performance car market.

Radial

The 'R' in the middle of the code tells us that this is a radial tyre rather than a cross-ply. Do not mix radial and cross-ply tyres on the same axle as this is illegal in many countries. In fact it is better not to mix the two types at all.

Wheel Diameter

The '16' refers to the wheel diameter in inches.

Safe Load

The '80' is a load index and refers to the maximum safe weight the tyre is designed to support. This code can range from 60 to 130 and corresponds to a weight from 250kg to 1900kg.

Speed Rating

The final letter, in this case 'T', is a speed rating which refers to the maximum speed at which the tyre can support the safe load. There is a range of over a dozen speeds that vary from 120kph to 300kph, each designated by a single letter.

If you have owned you vehicle from new, simply replacing like for like is the answer. If you own a caravan that was bought as a used vehicle you can't really be confident that the tyres are the correct size and type. In fact it's not unheard of for a used caravan or trailer to have tyres of different size or type on each side! In such cases, take care and take advice from a tyre supplier used to dealing with towed vehicles, or better still from the manufacturer.

Please feel free to contact Adrian on 01257 260577 or 07976 418093 for help and advice.