Otto Explains — Tyres
When Should You Replace Your Car Tyres?
Short Answer
Replace a tyre when the tread is worn to its wear indicators, when it is about ten years old, or straight away if the sidewall is damaged. Tyre makers put the wear indicators at 1.6 mm, count the ten years from the date of manufacture even if the tyre still looks fine, and treat a bulge, a deep crack, a cut or a puncture in the sidewall as reasons to replace it. Tyre makers also advise a yearly professional check once a tyre has been in service for five years. A tyre with a bulge or serious sidewall damage should not be driven on: stop somewhere safe and use the spare or call for roadside assistance.
How can you tell the tread is worn out?
Tyres have small bars, called tread wear indicators, moulded into the grooves of the tread. When the surface of the tread has worn down to the level of these bars, the tyre has reached its minimum tread depth and needs replacing. Michelin and Continental both put that point at 1.6 mm. Look at several places across the width of each tyre, because tyres don't always wear evenly. Otto hasn't found an official Omani source that sets a legal minimum tread depth, so this article doesn't state one; 1.6 mm is the tyre makers' replacement point.
Why does a tyre's age matter, even with plenty of tread left?
Tyre rubber slowly degrades with heat cycles, sunlight (UV) and ozone, and how long a tyre lasts depends partly on the climate and how the car is driven, so heat and strong sun are worth taking seriously in Oman. Ageing can't be judged reliably by eye: a tyre can look usable and still be due for replacement. Michelin advises a thorough check by a tyre professional every year once a tyre has been in service for five years, and Michelin and Continental both recommend replacing a tyre ten years after it was made, whatever its tread or appearance, including the spare. Some vehicle manufacturers set a different age, and their guidance comes first. A tyre's age is shown by the four-digit date code on its sidewall: the first two digits are the week and the last two the year.
Which kinds of damage mean a tyre must be replaced?
A bulge or bubble on the sidewall means the tyre's internal structure is damaged. It can lose pressure suddenly or blow out, so the tyre has to be replaced. A cut or puncture in the sidewall can't be repaired either, because the sidewall flexes constantly. Fine cracks in the rubber are a sign that the tyre is nearing the end of its life; cracks that are deep, numerous or open up as the tyre flexes mean it should be replaced. Hitting a kerb or a pothole hard can cause a bulge, so have the tyres checked after an impact like that.
When should you stop driving on a tyre?
Stop somewhere safe as soon as practicable, and don't continue on that tyre, if you see a bulge, a deep cut or exposed cords in the sidewall, if a tyre is visibly losing air, or if the car suddenly starts to vibrate, pull or handle differently. A bulge often causes an unusual vibration, and a damaged tyre can fail without further warning. Use the spare if it is safe to do so, or call for roadside assistance; don't drive on to a workshop on a damaged tyre. Vibration and pulling can also come from wheel balance, alignment or other parts of the car, which the article on steering wheel vibration explains.
Who should check and replace your tyres?
Tyre replacement is a job for a tyre specialist; AutoTronix offers no tyre services. Checking tyre condition is still part of owning a car: look over the tread and sidewalls regularly, and before a long journey make tyres, including the spare, part of the pre-trip checks Otto recommends.
Common Questions
- Can a tyre with plenty of tread still need replacing? Yes. Michelin and Continental recommend replacing a tyre ten years after it was made, whatever its tread, and age-related deterioration can't be judged reliably by eye. Sidewall damage such as a bulge, a cut or a puncture also means replacement, however much tread is left.
- Can a puncture in the sidewall be repaired? No. A cut or puncture in the sidewall can't be repaired, so the tyre has to be replaced.
- Does the spare tyre need replacing too? It ages like the other tyres, whether or not it has been used. The ten-year recommendation from Michelin and Continental includes the spare.
- Is 1.6 mm the legal tread limit in Oman? Otto hasn't found an official Omani source that confirms a legal minimum tread depth, so check the current rules with the Royal Oman Police. The 1.6 mm figure is the point at which Michelin and Continental say a tyre must be replaced.