Smooth Tyres

by Susan Mottram

“Considering that smooth and damaged tyres cause tyre blow outs and impair a vehicle’s braking system, leading to road accidents, injuries and death, and that an insurance company may reject an accident claim as a result of unroadworthy tyres, it is vital that drivers ensure that the tyres on their vehicles are in good order,” urges Garth Johnson, CEO of DEKRA Automotive.

DEKRA is South Africa’s largest roadworthy testing and vehicle inspection company with 42 branches nationwide.

“Although you may be fortunate to walk away from a crashed vehicle that has unroadworthy tyres, you are likely to be severely financially set back if your insurer finds your vehicle to have defective tyres, disputes the roadworthiness of your vehicle and refuses to pay out for the accident damage. Add that to injury to you, your family and other road users that smooth tyres can cause, and it’s not worth cutting costs by neglecting to replace damaged tyres.”

What the law says

It is illegal to drive on a tyre that could pose a danger to other road users or has been fitted to the rim incorrectly.

In terms of the law, the tread on tyres must be at least 1 mm deep across the tyre’s entire width over the full circumference of the tyre – this is the legal limit, but 1.6 mm is safer. The canvas cord or steel belting must not be visible on the tyre’s surface and the sidewalls must be free of deep cuts, lumps or bulges. Motorcycles may not use retreaded tyres. On motorcycles 50 cc or less, the tread pattern must be visible on 80% of the tyre’s width.

What Arrive Alive says

Studies of tyre safety show that maintaining proper tyre pressure, observing tyre and vehicle load limits, and inspecting tyres for cuts, slashes and other irregularities are the most important things you can do to avoid tyre failure, such as tread separation or blow out and flat tyres. These actions, along with other care and maintenance activities, can also:

• Improve vehicle handling
• Help protect you and others from avoidable breakdowns and accidents
• Improve fuel economy
• Increase the life of your tyres

Non-roadworthy tyres

A tyre that has insufficient tread or has a cut or is damaged in other ways decreases the tyre’s ability to hold the road, thereby both compromising the vehicles braking system and raising the risk of the tyre bursting while the vehicle is in motion. A common and extremely dangerous defect is an internal cut, sometimes caused when a tyre strikes a pothole, which leaks air into the sidewall of the tyre causing it to bulge. If the bulge bursts, the tyre will fail catastrophically.

While minor damage to a tyre may be able to be repaired, there is no safe and roadworthy solution for bald or bulging tyres except replacement. It won't help if you have the best brakes on the market, but your tyres are worn or badly fitted.

The dangers of driving with smooth tyres:

• Smooth tyres have an impact on braking distances. This means that you will have to travel further before your vehicle brakes to a full stop.
• Smooth tyres affect the road holding of your vehicle, as a result the tyres cannot grip the road as they should, which can cause your car to skid or slide on the road and crash into obstacles.
• Smooth tyres do not displace enough water on wet roads, which drastically impedes your vehicle’s ability to safely navigate in wet weather.
• Smooth tyres can damage your car’s suspension. This means that your vehicle’s ability to stick to the road and brake is affected even after you have replaced the defective tyres with roadworthy ones.

What DEKRA says

Johnson advises motorists to check their tyres at least once a week for tyre tread, cuts, bulges and bruises. Motorists should also check for nails and other articles that may have penetrated the tread. “If you are unsure of your tyres, contact your nearest DEKRA branch for assistance,” says Johnson.

DEKRA: No Mobility without Safety

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Research references for this article:

• Road Safety / Tyre Safety
• The Official K53 manual