Buying tyres online is easy and affordable. However, finding the right tyre size is downright difficult. Tyre sizing is indicated by a specific formula that is emblazoned onto the sidewall of the tyre. Tyre manufacturers and dealers know the formula and what it indicates and they can pick the right tyre for your car. However, it is necessary for you to understand tyre sizing as well, so that you buy the right tyres for your car.
Read on to resolve the mystery behind the seemingly ‘confusing’ markings on the tyre sidewall, which indicate tyre size.
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| Source: Outreachpanel |
The tyre size notation is prominently visible on the tyre sidewall in the form of a numerical formula. The formula contains information about size, dimensions, composition and capabilities of the tyre. For example, a typical tyre size notation is given like this: 205/65 R 15 95H. In this particular notation, the numbers and their location signify the following information –
- 205 - The first numeral in the notation indicates the width or section width (diameter) of the tyre in millimetres
- 65 – The second number indicates the sidewall profile. This number actually represents a ratio called the aspect ratio. This ratio indicates a comparison of actual tyre section height with its section width. As a result, if the number is 65, it is actually indicates that the height of the tyre is 65% of its width.
- R – This alphabetic notation indicates the construction of the tyre. R indicates a radial ply construction and almost all tyres have this notation as almost 90% of all tyres have radial construction.
- 15 – This number indicates the nominal diameter of the wheel rim. This number is represented in inches (and not millimetres).
- 95 – This is the last numeral in the formula and it indicates the load index. The load index offers information about the amount of weight the tyre can carry. For example, some vehicles have to carry a higher load and hence need tyres with greater load index.
The optimal load index of the tyres for a particular vehicle is indicated in the manufacturer’s manual and this number will be often combined with additional markings like RF that means reinforced and XL that indicates extra load capability.
- H – This last alphabet indicates the car tyre speed rating. For example, in this case, the numeral ‘H’ indicates that the tyre can support speed in the 210km/h or 130mph range. Essentially this parameter indicates the maximum speed of your car, which the tyre will support.
Each tyre manufacturer may have slightly different car tyre speed ratings. Obviously high performance cars demand tyres with higher speed rating as compared to regular day to day city driven cars.
Your local tyre specialist can offer you guidance on the best tyre size for your car, depending on various factors including what kind of car you drive (obviously), your driving style, whether you carry high load and other important factors.
Additional Notations on the Tyre Sidewall
The above-mentioned formula is standard in the tyre industry but manufacturers may and often do add extra notations depending on country and tyre quality.
For example, the letters DSST / RFT / ROF or RunFL indicate a version of run-flat tyres.
The notations TL and TT indicate a tubeless tyre and TL/TTv indicates a tubeless tyre that can be also used as tube tyre.
The world of tyre sizes is vast and can be confusing. But once you are armed with the basic information, reading tyre sizes is no longer a mystery.
About Author:
By Azzam Sheikh
This article has been written by Azzam Sheikh, expert tyre size reader and consultant – Tyre-Shopper UK.
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