This weekend, the Japanese Motegi facility will host the 15th MotoGP World Championship. Built by Honda in 1997, this facility is composed of a 2.4 km oval track and a 4.8 km road circuit known as the Twin Ring, where the riders in the queen class are scheduled to compete.
The Twin Ring introduces very few fast curves and a lot of slow curves that are spaced out with medium-length straightaways. Every lap, the MotoGP riders face 5 curves (1, 5, 9, 10, and 11) at a speed below 100 km/h.
The abundance of curves taken in second gear requires the riders to apply the brakes for an extended period of time: four seconds and four-tenths in curve 11, four seconds and one-tenth in curve 3, and four seconds in curve 1, just to name the most significant.
As a result,
it is difficult to cool the discs between one cut away and another.
A good grip level is added to all of this, improving the possibility of efficiently unloading braking torque to the ground and, as a consequence, increasing the stress that the brakes are under.
That is why the Twin Ring at Motegi is the World Championship circuit that puts the greatest amount of stress on the braking system. So, the Federation of International Motorcycling (FIM) has established regulations for this circuit that require MotoGP bikes to be equipped with 340mm discs. On the other tracks, however, the teams are still able to choose between 320mm and 340mm discs.
Brembo introduced the larger-sized, 340mm diameter discs in 2013. Last year, FIM made the 340mm discs obligatory at Motegi and optional at Montmelo and Sepang. Then, in May, it heeded the request of the Safety Commission and modified the regulations, permitting the use of 340mm discs on all of the tracks.
The exception remains Motegi where 340mm discs are still a requirement.