In order to find the right tyre for your car, it is necessary to know the 4 values that make up the tyre size.
Width – it is a key value which is at the beginning of the sequence of characters and is expressed in millimetres (e.g. 155/, 165/, 175/). The tyre width is the distance from the extreme point of the outer sidewall and the furthest point of the inner sidewall.
The profile of a tyre is given as a percentage and indicates the height, i.e. the percentage ratio of the height of the tyre sidewall to its width (e.g. 235/55 R18 means that 55 is 55% of 235). The letters R or D indicate the tyre type – radial or diagonal. The diameter of the wheel in inches is given last.