In a test performed at our test location called Contidrom, the braking distance was increased by 6.9 metres on tyres with the legal minimum tread depth of 1.6mm, compared to the full tread depth of 8mm. Tyres with a 3mm tread only took 2.7 metres longer to come to a full stop.
Tyre tread depth Indicators
Tyres have tread across their entire circumference. Tread depth measurements must be taken (for example using a depth gauge) in the main grooves that feature Tread Wear Indicators (TWI) on modern tyres.
In most European countries, the legal minimum tread depth for car safety is 1.6mm; that's when tyres are due for replacement.
To ensure that tyres offer the best possible performance, check your tyres regularly and consider replacing in good time. Furthermore, fit all four wheel positions with tyres of the same tread pattern design. At a minimum, each axle should have tyres with the same tread depth.
To better help determine the remaining tread depth, we have fitted “wet indicators” between the grooves of the tyre tread. These indicator ribs stand 3mm high, located between the tyre tread blocks.
If the surrounding tread has worn down to the level of the indicators, then it's time to consider fitting the wheels with new tyres as a preventative safety measure.
What to do in the event of aquaplaning
Whether your tyres are new or old, drivers should always slow down on wet road surfaces to reduce the risk of aquaplaning.
If aquaplaning should occur – which is still possible depending on weather and road conditions that a driver cannot prevent – drivers are advised to immediately take their foot off the accelerator pedal and depress the clutch. Avoid moving the steering wheel or braking suddenly.
However, if there is a danger of a collision or severe accident, the emergency brake should be initiated at once. In most cases, the rear wheels will still have enough grip to slow the vehicle.
As soon as the tyres are back in contact with the road and traction is regained, it should be safe to continue driving at reduced speed.