Currently in the United Kingdom there is a major campaign from the road safety sector, backed by Independent research performed by the Motor Industry Research Association (MIRA), to increase the minimum tread depth to 3 mm. This is based on research results proving that 3 mm tyres are 25% more effective on wet roads than 1.5 mm tyres.
The salient point here is that 1.5 mm tyres take 7.8 metres longer to stop at 80 kph than 3 mm tyres. This research relates to stopping in a straight line but even more significant is the degradation in cornering ability in wet weather; a factor of great importance on New Zealand’s winding roads.
Bettertyres advocates that the WOF minimum tread be increased to 3 mm which would be a useful buffer given the recent changes to WOF testing.