Unscrambling The Tyre Sidewall Symbol Mystery

19thJune08The sidewall of a modern car tyre is at first sight a confusing mixture of numbers, letters, codes and symbols that means absolutely nothing to the man in the street! And yet cracking the code reveals a whole load of useful, important and necessary information.
The tyre is arguably the most important safety component on a vehicle, only four patches of rubber, each no larger that the palm of a hand, are all that connects the vehicle with the road surface. There are now so many types of tyre available for different applications and with the increase in the purchase of tyres over the internet, when it is necessary to provide correct size and related information – all these vital details are contained on the sidewall.

According to TyreSafe, British motorists are woefully ignorant when it comes to the tyres on their cars. A recent poll conducted by the UK’s leading tyre safety organisation revealed that a staggering 80% of motorists did not know the legal minimum tread depth and a large percentage have no idea what the symbols on a tyre sidewall denote – many do not know which size of tyre they need in the event of a replacement.

TyreSafe has produced a leaflet entitled Car Tyres and Your Safety, available to download from www.tyresafe.org, which contains an illustration and a simple explanation of what all the symbols, letters and numbers on a tyre’s sidewall actually mean. Here are the details to crack the code:

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 week 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 the 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 only. These tyres have different tread patterns on their inner and outer sides, offering improved performance, and must be fitted correctly.

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

TyreSidewall

Note to Editors

TyreSafe is a not-for-profit, non-commercial organisation set-up to promote tyre safety and raise the awareness of the dangers of driving on defective or badly worn tyres. Illegal and worn tyres are a contributory factor in many road collisions particularly in the wet. TyreSafe campaigns for good tyre husbandry – look after your tyres and your tyres will look after you. For more tyre safety information visit www.tyresafe.org.

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This article was posted on 19th July 2011 in Latest News

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