TALKING TYRES by Robin Roberts (and Miles Better News Agency).
Washing a car the other day and my eyes were attracted to the tyres, specifically what all those numbers and letters might mean…
It was just as well because two needed changing and I know it’s important to get not only the correct size but also their loading weight, as set out in the manufacturer’s handbook.
They might all look the same, but there’s more to those black and round tyres on your car than meets the eye.
If you get the chance to look at the sidewalls, you’ll soon realise that there’s way, way more, in fact.
And while it might not mean a great deal to the untrained eye the small print should tell you one thing; when purchasing replacement tyres for your vehicle it’s important to replace them with the correct specification – often like-for-like.
There is a lot of small print on car tyres. The most important features of a tyre are its size, load rating and speed rating. (This applies to premium brands just as it does budget tyres or all-season alternatives).
Here are what the markings on the tyre sidewall mean for a typical tyre. For the purposes of this story, let’s say a 205/55 R16 91V:
205: This is the tyre width in millimetres.
55: This is the height or profile of the tyre sidewall (aspect ratio), expressed as a percentage of the tread width. In this case, the height of the tyre sidewall is 205×0.55 = 112.75 mm. R16: is the diameter of the wheel rim measured in inches – the wheel rim is 16″ in this case. 91: This is the ‘load rating’ of the tyre, it’s a measure of the maximum weight it can support, 91 denotes a load rating of 615kg.
V: The speed rating of the tyre, the maximum speed at which the tyre can support maximum load. This should be higher than the maximum speed of the car. In this case ‘V’ means a speed rating of up to 149 mph.
And there’s more!
E4: This is a European type approval indicating it has meet tyre safety standards set by the European Regulatory Authorities. In this case the 4 = Holland, the country where homologation has been obtained. Tyres cannot be sold in the European market without this European type approval mark and number.
Additionally all tyres manufactured for sale must bear a D.O.T code. This stands for Department of Transport. Originally this was mainly for tyres sold in the North American market but is now widely used all around the globe. This code more importantly denotes the date of manufacture.
On passenger car, motorcycle & truck tyres, the DOT code is made up of 4 parts and is a combination of numbers and letters. (For example: 7G 8K P5Y 4514).
This is what the unique letters and numbers mean:
7G: Manufacturer & factory where tyre was produced.
8K: Tyre size code.
P5Y: Denotes pattern / version (optional code).
4514: Refers to week and year the tyre was produced (date of manufacture).
Additional markings on the tyre will be the max load rating, in the case of this tyre it will look like this: MAX LOAD 615 kg (1355 Ibs). The maximum inflation pressure displayed as: MAX INFLA.PRESS. 300 KPa (44 PSI).
What if you’re driving on a run-flat tyre?
If the tyre is a run flat (self-supporting tyre), the tyre will have one of the following markings on the sidewall:
FT – Run Flat Technology.
RSC – Run Flat System Component.
BSR – Bridgestone Support Ring.
As Bridgestone offers a wide range of OEM tyres, depending upon the vehicle manufacturer and requirements, you may also see the following (homologation) markings on the tyre sidewall:
NO, N1, N2, N3 & N4 = Porsche Fitment
* (Star marked) = BMW approved
MO = Mercedes Original
MOE = Mercedes Only Extended
AO = Audi Original