| ody"> | | | | tyres your car was wearing at the time. Speed |
| âWeâre on your side.â This | | | | ratings run from âLâ (75 mph) to |
| sounds like the tag line in an advertisement but here | | | | âZâ (150 + mph). Currently, H-rated |
| it refers to the codes on a car tyreâs | | | | tyres (130 mph) hold the largest percentage of new |
| sidewall. Most of us know the obvious ones like | | | | tyre sales. |
| those referring to wheel diameter and tyre section. | | | | So much for speed, what about load? Yes, car tyres |
| There are, however, many other pieces of vital | | | | tell you about the load they are capable of carrying, |
| information to be found, moulded into the sidewall. | | | | They have a marked load index (LI), which is valid |
| Letâs consider some of the more important | | | | for sub-130 mph speeds. Load indices range from 50 |
| ones. | | | | (190 Kg) to 169 (5,800 Kg) but the calculations are a |
| Did you know that some car tyres have a marked | | | | touch complex. Letâs say you have a car |
| rating that indicates how well they handle heat build | | | | that weighs 2 tonnes, or 2,000Kg. Divide this by four |
| up? If you see a mysterious âAâ | | | | to get the weight on each wheel; this equals 500Kg. |
| on a tyre, it has the highest rating. A | | | | So far so good, but, do you know that all four |
| âCâ denotes the lowest. | | | | wheels carry 500Kg or is one end of the car heavier |
| The traction rating shows how well a tyre can stop | | | | than the other? In practice, itâs usual to add |
| you on a wet road. This rating goes from | | | | a percentage to cover such factors. |
| âAAâ to âCCâ. No | | | | In our example, then, the car needs tyres with a load |
| prizes for guessing which is the best. | | | | index of 84. We can add 20 percent, giving a weight |
| Now for some numbers. Tread wear ratings go from | | | | bearing capacity of 600Kg. Therefore tyres with a |
| 60 to 600 in increments of 20 and the figure shows | | | | load index of 90 will do very nicely. In reality, a car |
| how long the tyre is expected to last. In theory, a | | | | tyreâs load rating will exceed its actual |
| tyre marked â200â³ should last twice | | | | needs by a long way. However, when speeds reach |
| as long as one marked â100â³. This is, | | | | 130 mph or more, the load index calculations change |
| however, a relative rating. The actual tyre life will | | | | dramatically. For reasons far to technical to explain |
| depend on many factors, including your driving style, | | | | here, the theoretical load rating decreases as road |
| the road surfaces encountered, correct wheel | | | | speed rises. In the event you run a very, very fast |
| alignment and the right tyre pressure. Think | | | | and heavy car where the speed cameras |
| âbenchmark.â | | | | donât work, there are experts in such |
| The speed rating a tyre carries is extremely | | | | matters. Find one! |
| important. Using over-specified tyres is a (very | | | | Lastly, you should never use a tyre more than 6 |
| expensive) upside here; tyres for high-speed use can | | | | years old. The date of manufacture is part of the |
| be used at lower speeds. On the other hand, if the | | | | DOT code marked on one sidewall. For example, a |
| speed rating is too low and you have an accident, | | | | tyre marked â2709â³ was made in |
| your insurance company may take a dim view of the | | | | the 27th week of 2009. |