How to Tell If a Tyre Is Worn: Tread Depth, DOT Code and Cracks

The legal minimum tread depth in Switzerland and across the EU is 1.6 mm. Below that, a tyre is illegal and genuinely dangerous — on wet roads, grip drops sharply because the tread can no longer channel water away (aquaplaning). Industry tests consistently show braking distances on wet surfaces already increase noticeably once tread falls below 3 mm.

Every tyre has built-in wear indicators (TWI) — small bars inside the tread grooves, marked by a triangle on the sidewall. When the tread surface levels with these bars, the tyre has reached the 1.6 mm limit. A quick home test: slide a 5-franc coin into the groove — if the coin's rim shows above the rubber across most of the tyre, it's time to replace it.

Also check the DOT code moulded into the sidewall: the last four digits show the week and year of manufacture, for example 2419 means week 24 of 2019. Rubber ages chemically regardless of mileage — tyres older than 6 years need a thorough check, and after 10 years should be replaced regardless of appearance.

Cracks on the sidewall (a spider-web pattern) signal rubber ageing. A localized bulge (hernia), caused by hitting a kerb or pothole, means immediate replacement — the tyre can blow out without warning.

Wear in the centre of the tread usually points to overinflation, wear at the edges to underinflation, and uneven, one-sided wear usually signals a suspension or alignment problem.

Not sure about the state of your tyres? Stop by — we'll check them for free in 10 minutes and give you an honest answer.