These are lightweight, no more than 2cm wide and pumped to levels of 150 pounds per square inch compared to approximately 25psi on a family car.

The surface area in contact with the road is as low as possible to cut down on rolling resistance, which means descents of up to 60 miles per hour require total concentration and a lot of guts.

Most tyres are tubular - a one-piece design glued to the wheel, although the inner tube design found on normal bikes is becoming more common as materials become lighter.

The main problem, as with any bike tyre, is the humble puncture - and team mechanics have to be ready to leap out of the following team cars to change a wheel at a moment's notice.