2 types of thumb master cylinder systems
The types of brake master cylinders available for the teams differ in terms of wheelbase, in order to adapt both the race and the “reactivity” of the control as a function of the rider’s feeling. In addition, each motorcycle features the
remote adjuster, used by the rider’s left hand to vary the position of the brake lever even while lapping the circuit. According to Brembo,
more than one-third of MotoGP riders, regularly use
the thumb master cylinder. This technical solution, introduced by Brembo in the 90’s to support Mick Doohan, allows the activation of the rear brake by pressing a special lever placed on the left semi-handlebar and actuated by the riders thumb.
Two variants of the thumb master cylinder systems are in use for the 2020 season: the most widespread features a
unique circuit of thumb master cylinder and pedal, using a rear two-piston caliper. Instead, the alternative, features
two separate circuits, each of which acts on two of the four pistons of the rear caliper. In the first option a system excludes the other, in the second they can act simultaneously. Starting from 2019, the teams can also use
a variant of the classic thumb pump, which is called
push & pull pump. This new design is optimized to guarantee the maximum efficiency, it has a dual function and
can be operated both by the thumb or index, depending on the rider's preference. The use of this pump with the index requires it to be mounted on the lever with a rotation of 180° compared to the use of the thumb: this increases the modulation and the grip on the lever during deceleration.