Tyre Safety, Fitment and Road Safety
Tyre failure is a vital factor in thousands of road accidents every year. Research by the CSIR indicates that nearly 20% of accidents involving minibuses have tyre failure as a contributing factor. It won't help if you have the best brakes on the market, but your tyres are worn. When braking, the idea is to have sufficient friction between the road surface and tyre to bring the vehicle to a standstill. If the tyres are worn there will not be enough friction and the tyre will slide over the road surface, not stopping the vehicle. This is also true for handling and steerability. Look after your tyres!
Car Magazine online points out some rules for ensuring you have correct, safe tyres on your vehicle:
- Tyres should always be replaced with the same size designation as recommended by the vehicle or tyre manufacturer.
- Guard against used tyre imports, many of which are beyond retreading but are retreaded and sold illicitly. Similarly, watch out for counterfeit tyres - illicit copies of respected brands. The advice is to always look for the SABS stamp of approval.
- All four tyres should be of the same size, speed rating and construction (radial or cross-ply).
- When two radial tyres are used with two cross-ply, put the radials on the rear axle. In some cases (especially commercial vehicles) the manufacturer might recommend different-sized tyres for the front and rear axles.
- Never assume that the tyres on your vehicle are correct, even if you have newly purchased it. Unless you bought new from an authorised dealer your vehicle may already be fitted with potentially lethal tyres.
Overinflation/ Under Inflation and Safe Driving
Over and under-inflation reduces tyre to road contact and shortens tyre life. The tyre responds in the same manner to under inflation as to overloading. The same applies to over inflation / under loading.
- Overinflation / under loading - Reduces cushioning power of a tyre. A tyre is more susceptible to impact, penetrations and abrasion. Reduced road-tyre contact. Negatively affects the handling characteristics of the vehicle. (Excessive centre wear.)
- Under-inflation / Overloading - The biggest single cause of "burst" tyres. Under-inflation causes excessive flexing of the tyre sidewall which leads to overheating and ultimately, casing break-up and treads separation. Reduced tyre-road contact leads to poor handling and faster wear. (Excessive shoulder wear.)
- Check tyre pressure once a week or before undertaking a long journey
- Check tyre pressure early morning (low ambient temperature)
- Only use tyre sizes recommended by the manufacturers at the recommended inflation pressure
- Cuts in the tyre could permit damp to reach the casing plies. This is harmful to both textile and steel casings and will affect safety and tyre life.
- Wheel alignment - misaligned wheels will lead to excessive tyre wear. A worn steering mechanism, ball joints and wheel bearings will also reduce tyre life.
Consult your vehicle manual for the proper size and speed rating. Some tyres are now marked with letters to indicate their speed ratings. Tyre speed ratings do not imply that vehicles can be driven safely at the maximum speed for which the tyre is rated, particularly under adverse road and weather conditions, or if the vehicle has unusual characteristics. No matter how good your car, or its tyres, this is not justification for breaking speed limits. If a tyre burst, do not apply the brakes, rather use the momentum and gears to slow down the vehicle. A sudden change in direction or braking will result in loss of control over the vehicle. Rather lose one rim than your car and probably your life!
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