When we talk about the diameter of a brake disc we come from the fact that each disc is designed to be able to stand the pressure of the brake calipers, the weight of the motorbike and the speed of moving when braking.
Summing up what’s above, a designer thinks about the material, the thickness and the diameters according to each model of motorbike and exponentially the limit that the physics suggests to guarantee a correct functioning of the disc is exceeded.
That’s why it draws our attention that sometimes we are asked if the bigger diameter of the disc, the better braking. The simple answer is yes, obviously if the surface is bigger and the surface attrition path is higher physically it must brake better, but…
We must remember that in a braking system other components intervene. Direct from the system itself, discs, pads, calipers, hoses, handles and/or pedal, or indirect to the system like the tires and the shock absorbers.
Each and every one of these components are extremely important when braking, almost as important as the touch and the ability of the rider. Many of them decide to give an order of merit putting the tires first and the pads after. The order is not determining, we must have all the system in perfect conditions. In what way is it useful to have new tires if the hoses don’t have rigidity and they don’t action the calipers enough? We definitely need to consider the whole system.
A disc with a bigger diameter, as long as the motorbike model can have it, gives us a better surface and due to laws of physics a bigger surface path of the disc so the pads bite strongly (clamping force) at the moment of braking, anyway a double disc will give us a better braking but not exponentially the double of it.
Another important detail has been the adding of radial clamps that have allowed a reduction of the disc diameter with the same safety. The difference with the axial clamps is the given rigidity. The radial ones are mounted directly to the pin and with screws perpendicular to the disc, something that’s translated to a certain flexibility with regard to the radial ones.
Opportunely we already talked about how to improve the braking system of your motorbike, you can remember this issue here.
All these improvements come from the competition world and NG Brakes directly participates on this progression constantly giving test pieces to the riders that give their opinion, which is translated to the street models in favor of a bigger security.