To match the new GP4 caliper, Brembo gives riders a choice of eight carbon fiber discs. There are four disc diameters, ranging from 320 to 340mm. Among those four choices, each disc is available in Low Mass and High Mass carbon compositions. Beyond that, there are two different carbon compounds for the brake pads. All of these choices allow the discriminating rider to customize the brake response to his preference and needs.A Brembo spokesman outlined the advantages of carbon fiber for brake discs, saying, “Carbon ensures a triple advantage—a reduction of unsprung mass, an identical friction coefficient from the start to the finish line, and an absence of residual torque issues that can come from the use of steel discs.”Many fans may not know that one-third of the MotoGP grid uses a thumb rear brake—a technology that dates back to Mick Doohan in the 1990s. The MotoGP racers have a choice of two thumb master cylinder braking systems. The standard system uses the thumb and pedal together to actuate the two-piston caliper. In the other, there are two separate circuits, each working on its own pair of pistons in the caliper. Further, there is an option that allows the rider to use either his thumb or index finger to actuate the rear brake.Although Brembo doesn’t have quite the braking dominance in Moto2 and Moto3, it has a strong presence. Ninety percent of Moto2 and Moto3 teams use Brembo calipers and master cylinders, with 75 percent using Brembo pads, and about half using Brembo’s steel discs.