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Step 1: measure tread depth
The UK legal minimum is 1.6mm across the central three-quarters of the tyre's width around the full circumference. Most manufacturers recommend replacement at 3mm, and on a heavier SUV that's the threshold worth working to. A tread depth gauge gives you an accurate reading. For a quick check, insert a 20 pence coin into the tread groove: if the outer band of the coin is visible, the tyre is approaching or below the legal limit.
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Step 2: Inspect the sidewalls
Run your eye and your hand around the full circumference of each tyre. Bulges indicate internal structural damage, usually from a sharp impact. A bulging tyre is at immediate risk of failure; take it off the road. Cuts and cracking are also worth acting on, particularly if they're deep or widespread.
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Step 3: Read the wear patterns
Uneven wear is the tyre's way of telling you something's wrong elsewhere on the vehicle. The table below covers the most common patterns and what they indicate.
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Step 4: check the valve caps
A missing or damaged valve cap allows moisture and grit to reach the valve core, which causes slow leaks. Replacement caps cost very little and take seconds to fit.