Thumb Brake in Racing Competition

The thumb brake in the world of racing is not a recent invention. On June 26th, 1992, during the Dutch Grand Prix at Assen, Mike Doohan suffered a serious crash that severely injured his right leg.

This incident led to a modification of his braking system: an additional lever was installed on the handlebar grip, allowing him to operate the rear brake with his thumb, replacing the traditional foot pedal.

This system has been tested and used by several riders both in the MotoGP World Championship and in World Superbikes . While it does not provide a direct technical advantage, it does offer certain benefits in terms of riding control.

Some riders use it out of necessity after suffering injuries or discomfort in their right leg, which prevents them from operating the rear brake pedal normally.

Others adopt it for comfort in certain corners on specific circuits, especially those where a rider’s foot may scrape the asphalt or limit the lean angle.

And some riders — such as Andrea Dovizioso — use it as an additional tool for bike control, helping them manage rear-wheel slides without compromising foot position.

Another reason to install a thumb brake is to control excess power output, preventing the front wheel from lifting during acceleration (a wheelie).

With the left hand, pressure can be applied to the rear brake, helping the electronics keep the front end planted while the rider is fully opening the throttle with the right hand.

The thumb brake lever can be designed either as a push-type system (operated with the thumb) or as a pull-type system, in which case the rider uses the index finger.

Motorcycles may also include two separate braking circuits, allowing the rear caliper to be operated either by thumb/index finger or by foot.

This setup is used on certain tracks where right-hand corners with extreme lean angles make thumb braking more effective than using the foot pedal.

In the World Superbike Championship, motorcycles in this category are not allowed to use any disc material other than steel. The official disc diameters are 328 mm or 336 mm, depending on the braking demands of each circuit.

Currently, the circuit that puts the greatest strain on braking systems is the Chang International Circuit (Thailand), even more so than Monza (Italy), which ranks second in terms of braking intensity.