Every tyre's sidewall is packed with information that can confuse even long time professionals. Numbers and letters designate sizes, pressures, loads, where the tyre was made and when, and sometimes even whether your tyre complies with pass-by-noise regulations. To complicate matters even more, much of the information isn't measurement-standardized, or even applicable to the UK. Here's how to decode it all.
1. Brand or trade name of the tyre - i.e. Continental, Dunlop, Goodyear, Michelin, Pirelli etc.
2. Tyre model or pattern code - For example Sport, Pilot, Eagle etc.
3. Tyre size - The width of the tread expressed in millimetres, which in this illustration is 205; the aspect ratio – height of the tyre sidewall as a percentage of the width, in this case it is 55% of 205mm; and the diameter of the tyre’s centre hole, expressed in inches. In this illustration, it is 16”. The letter between the numbers is the type of construction i.e. ‘R’ Radial. So this tyre is a 205/55 R 16.
4. Service description - in this example the figure 91 denotes the maximum weight capacity of the tyre according to the official load index table, which translates to 615 Kg, The letter V indicates the speed rating of the tyre, in this case the tyre suitable for cars capable of reaching a maximum vehicle speed of 149.1 mph.
5. ECE (Economic Commission for Europe) Regulation 30 Conformity Approval Number – which means that the tyre meets the standards of the European Regulatory Authorities.
6. EEC Noise Approval Number - which means that the noise generated by the tyre is within approved European limits.
7. USA Department of Transport manufacturer’s code - This has no relevance to the UK market.
8. Date of manufacture - This is important as the age of a tyre can affect its performance. The first 2 numbers refer to the month and the 3rd and 4th numbers refer to the year.
9. USA UTQG (Uniform Tire Quality Grade) ratings - This has no significance in the UK.
10. USA maximum tyre loading - This has no significance in the UK.
11. USA maximum tyre inflation pressure - This has no significance in UK.
12. Denotes tubeless construction.
13. Safety warning refers to the dangers of under-inflation/overloading and the mounting of tyres together with the risk of severe over - inflation - This is particularly important as TyreSafe research shows that up to three quarters of cars on UK roads have incorrectly inflated tyres.
14. Direction of rotation which relates to directional tyres only - These tyres are designed to rotate in one direction only which is indicated on the sidewall by an arrow.
15. Outer/inner sidewall refers to the mounting of asymmetric tyres - These tyres have different tread patterns on their inner and outer sides, offering improved performance, and must be fitted.
16. Extra load version where applicable.
17. TWI indicates the location of the tread wear indicators, which are raised areas at the base of the tread to serve as a visual warning that the tyre is approaching or at the minimum legal tread depth.