What's the legal tyre tread depth for an HGV?

The number most people remember is for a car. Heavy goods vehicles are held to a different one, and it catches drivers out at the roadside.

Where the tread actually has to be

The 1mm isn't measured on one lucky spot. The law asks for a continuous band of at least 1mm of tread covering at least three-quarters of the tyre's breadth, and around its entire circumference. Unlike the car and van rule, the band doesn't have to be the middle three-quarters: any continuous three-quarters counts. The original tread pattern must still be visible across the rest of the tyre too.

In plain terms: a worn shoulder doesn't make the tyre illegal on depth as long as a continuous three-quarters band still has 1mm all the way round, but the original grooves must still be visible on the shoulder too. That's why a proper walkaround means running your eye (and a depth gauge) right across and right round each tyre, not just glancing at it.

Tread isn't the only thing that fails a tyre

Plenty of tyres are pulled at the roadside with legal tread. These are instant prohibitions regardless of how much tread is left:

What it costs if you drive on it

For a single bad tyre, DVSA can issue a fixed penalty: £200 and 3 penalty points for HGV tread under 1mm, £100 and 3 points for exposed cords or a bulge. Two or more bad tyres go to court instead. On a goods vehicle over 3.5 tonnes the maximum fine there is unlimited: it's a level 5 offence, and the £2,500 level 4 cap only applies to vehicles up to 3.5 tonnes. The court fines you per tyre. Endorsement is 3 penalty points, though a court will normally apply one set of points for several tyres found on the same occasion. An examiner will normally also issue an immediate prohibition, so the vehicle isn't going anywhere until it's put right. Four illegal tyres is a very expensive, very bad day.

The practical rule

Don't run a tyre down to the limit. 1mm is where it becomes illegal, not where it becomes worth changing. Uneven wear means part of a tyre can be under 1mm while the rest looks fine, so plan replacement with a margin, and record the check either way, because the paper trail is what protects you at audit.

A tread depth gauge and a tyre pressure gauge turn a borderline tyre into a measurement. What to look for in each is on our walkaround kit page, which contains Amazon affiliate links.