How to Read Tyre Sizes & Markings

225 / 55 R17

225 is the nominal tyre width in millimetres. 55 is the sidewall height expressed as a percentage of that width. R indicates radial construction. 17 is the wheel diameter in inches.

The full specification matters

Tyres also carry a load index and speed rating. These, along with your vehicle’s approved sizes and other requirements, need checking before purchase. Some vehicles use different front and rear sizes.

Where to start

Read the tyre sidewall, then check the vehicle placard or owner’s manual. A previous tyre replacement may not be the correct specification, so do not rely on the fitted tyre alone.

Once you have the full specification, prepare a tyre fitting and replacement enquiry. If your concern is steering or vibration, the alignment and balancing guide explains the different checks to discuss with the workshop.