It is recommended that you change your tyres when the tread depth is 3mm

Independent research performed by the Motor Industry Research Association (MIRA) has provided convincing new evidence that worn tyres significantly increase the chances of having an accident on wet roads by increasing the stopping distance.

The test results showed that significant increases in stopping distance began to appear when the tyre was worn down to 3mm. Although the legal minimum UK tread depth is only 1.6mm, this new research showed that tyres with a 3mm tread had a 25% better performance than those at 1.6mm in wet conditions.

In terms of stopping distance this represents an extra 8 metres (25ft). In one test, where a new tyre with a tread depth of 8mm was compared to one with only 1.6mm the stopping distance increased by 13 metres (42.25ft) - the equivalent to double the length of a typical living room.

In short, when you let your tyres wear down to the legal minimum of 1.6mm, it will take you nearly a bus length extra to stop from 50mph. Don't chance it.

The recommendation to change tyres at 3mm is currently supported by road safety organisations, including Roadsafe and RoPSA and leading European car manufacturers.