Considering that the tyre is the vehicle's only contact with the road, and therefore crucial to driver safety, it is amazing that so little attention is paid by the general public to proper tyre maintenance.

Tyre inflation pressures are no exception. In 2005 research carried out by the RAC Foundation found that as many as 7% of drivers checked their tyre pressures only once a year, whilst roadside checks by the Tyre Industry Council (now operating as TyreSafe) have consistently found a high proportion of tyres on the road to be incorrectly inflated.

The same report by the RAC Foundation also points out that 6% of all fatal motorway accidents are caused as a result of blowouts caused by under-inflated tyres.

So let's not underestimate the seriousness of the problem. If you do not check your tyre inflation pressures for months on end, your pressures may be incorrect and, if that is the case, the safety of your vehicle could be seriously compromised.

Let's take a look at the effects of under and over-inflation

Under-Inflation

Under-inflated tyres wear unevenly. In particular under-inflation causes rapid shoulder wear. Even if your tyres are only 20% under-inflated, this will result in a 25% increase in tyre wear, thereby significantly reducing your tyres' product life and increasing your overall tyre costs.

Under-inflation also causes increased flexing of the sidewalls, which results in increased heat build-up within the tyre, which in turn can lead to premature tyre failure. Even if the tyre does not fail, continuous use in an under-inflated state can cause irreversible damage to the tyre.

Handling characteristics can also be more difficult if a vehicle's tyres are under-inflated. Braking distances are also increased, thereby compromising safety.

The vehicle's fuel economy is also decreased if the tyres are run in an under-inflated condition. 20% under-inflation will typically result in a 3% reduction in fuel economy.

Over-Inflation

Over-inflated tyres are typically affected by poor handling, particularly when braking and cornering. This is because when you inflate the tyre above its recommended inflation pressures, you are reducing the size of the tyre's contact patch with the road surface.

Increased tyre wear is also a result of over-inflated tyres. In this case the excessive wear will be found on the crown of the tyre.

Over-inflated tyres are more subject to impact damage, which makes them more susceptible to premature failure.

Reduced comfort is a further result of over-inflation.

Practical Advice

In order to make sure your tyres are correctly inflated it's worth following the following simple rules

• 1. Make sure you know your recommended tyre pressures and adhere to them as closely as possible. The best place to look for your recommended pressures is in the car manufacturers handbook. Alternatively tyre dealers will often also have a tyre pressure chart on their wall which can be consulted. Failing this contact the technical department of your vehicle manufacturers and/or a leading tyre manufacturer, who should be able to provide you with the correct information.
• 2. Check your tyres regularly including the spare. Every two weeks is the recommended norm.
• 3. Check your tyres only when they are cold. Even a relatively short trip will result in the air inside your tyres heating up, which will result in an increase in pressure.
• 4. Overloading has the same effect as under-inflation - so if you are planning a long trip with a full car increase the pressures according to the manufacturers' handbook. Don't forget to reduce the pressures again on your return. On no account overload the vehicle beyond the manufacturer's specification. It is illegal.