A Guide to Car Tyres

Introduction

It would be fair to say that most motorists take car tyres for granted most of the time. Yes, motorists check their tyre pressures regularly, but above and beyond that it is only when they need to be replaced because of wear and tear, or damage, receive their full attention. Even then, it may simply be a question of conveying information from a tyre sidewall to a tyre fitter, or fitters, without necessarily understanding what that information means.

Car Tyre Considerations

The make and model of a tyre is usually written on the sidewall, so it is easy to determine whether you want, say, Goodyear Hydragrip, or Michelin Primary HP (High Performance) tyres, but the actual specification of the tyres may remain a mystery. After all, the only visible difference between one tyre and another is the pattern of the tread and this alone cannot tell you anything about the performance or longevity of a tyre, or its effect on fuel consumption.

Safety is paramount, so you need to choose tyres that are not only the correct size, but also load capacity and speed ratings that correspond to your car and the type of motoring that you want to do. To illustrate these points, let us consider another popular high performance tyre, the Uniroyal Rainsport, with a specification of 245⁄45R18 96W. The 245⁄45 tells us that the tyre is 245mm wide and that its profile is 45%. The R stands for radial, as opposed to cross–ply and the 18 tells us that its inner rim has a diameter of 18". The load capacity rating (96) and speed rating (W) are a little more difficult to decipher, since their values need to be looked up in tables. A load capacity rating of 96 means that this tyre is capable of carrying a payload of 710kg, while a speed rating of W means that it is safe for driving at up to 168 mph.

Whilst it is often true that you get what you pay for when buying car tyres, it is not always the case and even the best tyres while not perform optimally if underinflated. If you are intending to tow, say, a trailer tent, which tent you choose will also have a bearing on the tyres that you choose for the towing vehicle. Trailer tents are typically designed to be towed by an average–sized vehicle, but, even so, an additional weight of several hundred kilograms does place extra stress on tyres. As a word of caution, trailer tent wheels are generally 8" or 10" in diameter and therefore incompatible with standard car tyres.