Tread wear is a serious matter. Incorrect thickness significantly influences stopping distances of the car and crash speed in the event of an accident. Worn tyres substantially increase the risk of aquaplaning and drastically reduce braking performance on wet roads. Not by chance, a legal limit has been defined - specifically, 1.6 mm of minimum thickness – which, if not respected, can lead to fines or points being deducted from your driving license in Italy. However, as inspections are not that frequent, it is first and foremost a matter of common sense. In short, never drive with worn tyres.
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WHEN SHOULD YOU CHANGE YOUR TYRES?
Ideally, you should replace them when the thickness drops to 3 mm for summer tyres or 4 mm for the winter ones. In any case, you should never risk reaching the legal limit for your own safety and for that of your passengers. Wear is natural for the only component with which your vehicle has contact with the road surface. Tyres are made using an increasingly sophisticated blend of chemical ingredients, which provide apparently contradictory functions like road holding and rolling resistance on asphalt thatmay not always be in the best state of repair. This difficult balance between the elements is naturally disrupted over time. Exposure to sunlight - in the case of summer tyres - accelerates ageing, whilst rain and snow do not make the life of winter tyres any better. Over time, tyres tend to harden, especially in the tread area. With this loss of elasticity, the compound becomes less reactive to changes of temperature and to wet conditions. Remember also that incorrect wheel geometries and failure to swap the tyres can make the situation worse.
HOW DO YOU CHECK TYRE WEAR?
So, how do you check tyre wear before it is too late? A visual and tactile check of the surface is certainly an effective starting point to identify any irregularities. Pay particular attention to any signs of swelling and cuts, however small - they can deteriorate and cause serious problems at speed. Then measure the tread, going beyond the correct but not precise coin method (one Euro or two Euro coin, for summer and winter tyres, respectively) placed in the central groove. To make the check more scientific, you can look for the tread wear indicator. It is a small, 1.6 mm high block positioned inside one of the main grooves of the tyre. To find it, look for the letters TWI on the sidewall of the tyre. If the tread has worn down to a point of grazing the indicator, the tyres must be replaced as soon as possible. Another effective method is to use an instrument bought for just a few Euros called a tread depth gauge. Positioned in the tyre groove, it very precisely measures the tread and will tell you if it is time to go to a tyre fitter. It is worth repeating that, when it comes down to tyres, sensible choices are determined by common sense, not by the legal limit.