The UK legal minimum tyre tread depth is 1.6mm across the central three-quarters of the tyre. Driving below this limit in Cardiff carries a fine of up to £2,500 per tyre and three penalty points. But on Cardiff's frequently wet roads, experts recommend replacing tyres at 3mm tread — the difference in wet-weather stopping distance between 3mm and 1.6mm can be several car lengths.
The quickest check at home is the 20p coin test. Insert a 20p coin into the tyre's main tread groove. If the outer band of the coin is hidden, your tread is above the legal minimum. If you can see the outer band, your tyre may be illegal and needs replacing immediately. Repeat this in multiple locations across the tyre width and around the circumference, as tyre wear is often uneven — particularly if wheel alignment is off.
Uneven tread wear is one of the most useful indicators of underlying problems. Edge wear on both sides suggests under-inflation; centre wear points to over-inflation; wear on one edge only usually means wheel alignment is out. If you spot any of these patterns on your Cardiff vehicle, contact Royal Mobile Tyres on 029 22714889 for a free mobile tyre inspection at your home or workplace.