Brake discs are ALWAYS sold per unit and TRW offers a number of options with regard to design.
Standard brake discs are, well, standard. Dry but decent. The design of the RAC brake discs is more varied and playful. They are lighter and the extra cooling provided by the special design makes sure they can withstand the heat better. Ideal for more extreme circumstances.
A fixed or a floating design is not always a choice: the back brake disc is fixed not matter what, only in the front you can opt for both IF your motorcycle is equipped for it. This is the case with a number of BMW models but certainly not all. The benefit of floating brake discs is that they can resist higher temperatures better.
The choice for off-road-specific brake discs is worth mentioning as well: TRW developed EC-brake discs for the advanced gardening and mud works. The steel alloy used here, is built to last. The design looks good but it’s more eminent that controllability and brake reaction approach near-perfection.
General, about TRW brake discs
TRW offers brake pads and braking systems for the aftermarket that allow motorcycles and other vehicles to engage in supple, safe and powerful driving. And braking. Especially the latter is what matters most: as a motorbike rider you want to have a reliable braking solution - something which has been provided by TRW for about a century now.
One element that’s quite important in this phenomenon, is the brake disc. It can be said that the TRW units differ from the others. All the TRW brake discs are homologated, even if they were made for scooters. They have a slower wear and a TRW brake disc will outlast alternative aftermarket brake discs by 30%. The fact that TRW brake discs are made of tempered steel will have something to do with that. It creates brake discs that are resistant to distortion, all the while not giving corrosion the chance to form thanks to a special, new type of alloy. The precision used to grind the TRW brake discs (tolerance of 1/100mm) prevents vibration and ensures that the brake pads wear more evenly.