Confused about your tyre size? Here's how to end your confusion. There really is only one reliable way to find out your tyre size and that is by physically reading it off the tyre wall. In the image below we have shown an example tyre with a tyre size of 265/40 x17.

Please ignore any letters (e.g. R, HR, SR & VR) as these relate to the tyre construction type and have nothing to do with the tyre size. The tyre size in our example is 265/40 x 17 means:

• 265 is the nominal tyre section width in millimetres.
• 45 is the aspect ratio of the tyre; meaning the height of the tyre's cross section expressed as a percentage of its width. It is often called the tyre's profile. (as in low profile tyres)
• 17 is the diameter in inches of the wheel rim that the tyre is fitted to. (In a few cases some metric sizes also exist)

When obtaining snow chains it is vital that the vehicle's correct tyre size is specified. The wrong size will nearly always result in the chains not fitting. However, we always look out for this and double check whenever possible. An important point, often not appreciated, is that all tyre manufacturers build tyres to be within certain tolerances. The overall diameter for instance can vary by as much as +/- 3%. This means that occasionally a snow chain may be a perfect fit on a given tyre size from one manufacturer but could appear to be either loose or tight on another make or model of tyre. For this reason it is always important to make a test fitting before using chains in earnest.

Please rememember that the best and only way to check the tyre size is a visiual check of what is written on the side of the tyre. Do not rely on owners manuals or ringing the garage since this way mistakes can often be made.