The 20p test is the fastest free way to check whether your tyres are road-legal. Place a 20p coin into the main tread grooves of your tyre. If the outer band of the coin is hidden, your tread is likely above the legal minimum. If you can see that outer band, your tyre may be illegal and needs checking.
Why the 20p coin works
The raised outer rim of a UK 20p coin sits roughly 3mm from the edge. Because the legal minimum is 1.6mm, a coin that disappears into the groove gives you a comfortable safety margin. It's an indicator, not a legal measurement, but it's a reliable early warning.
How to do the 20p test step by step
- Park safely and make sure the tyre is cool and clean.
- Insert a 20p coin into a main groove around the centre of the tyre.
- Check whether the outer band of the coin is visible. If it is, get the tyre inspected.
- Repeat at the inner edge, centre and outer edge, and at three points around the tyre.
Test every tyre, in several places
Tyres rarely wear evenly. Worn shoulders often point to under-inflation or alignment problems, while a worn centre strip suggests over-inflation. Checking multiple points catches a tyre that's legal in the middle but bald at the edge. While you're there, look for cracks, bulges and embedded nails.
Failed the test? Don't risk it
If any tyre is borderline, replace it. Our mobile fitters bring budget and premium tyres to you anywhere across London and Birmingham, so you can swap a worn tyre on your driveway. Book online or call us for same-day help.
