In a message dated 24/07/2007 04:58:06 GMT Daylight Time, bones@xxxxxxx writes: The formula is 9 x SQRT(Tyre Pressure). That means for the average car with 30psi the aquaplaning speed is 50mph. Slower than that you just lose a bit of traction but at that speed enough of a bow wave is created ahead of the tyre to effectively start the vehicle surfing on the water. Once that happens there's not a lot you can do except sit back and enjoy the ride. Er.....Doesn't the tread have an effect here, as its a channel to disperse the water "cushion"? I understood that's why they have "wet" tyres. Frank T.