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Dry, wet and extreme-wet tyres 11 September 2005

Conditions at Spa threw tyres into the spotlight. This drawing illustrates the two extremes. Dry tyres have four longitudinal, parallel grooves. These grooves are 2.5mm deep, 14mm wide at the top of the groove and 10mm wide at the bottom. Extreme wets, only usable under instruction from the clerk of the course, have 50 percent less tread surface, grooves twice as deep as dries, and they can dissipate water at a rate of 35 litres per second at 300km/h. Between these two are wet tyres - 30 percent of dry tyre tread, grooves 3 to 3.5mm deep, and able to dissipate water at 15 litres per second.