AP Racing, has developed the CP5898, a new differential bore master cylinder, which enhances performance in racing applications. The cylinder is already in use in the NASCAR Sprint Cup Series, and will be available to other categories, such as F1, sportscars, touring cars and rallying in due course.
Its advanced design improves braking consistency by reducing unwanted, low pressure, pedal travel and operating at high pressure throughout brake actuation.
Low-pressure pedal travel is minimized thanks to the use of two bores connected by the same piston, with an external valve controlling the changeover between the two. The larger bore controls the initial brake travel by supplying a greater volume of fluid at lower pedal pressures, which eliminates any losses in the brake system. As the braking pressure in the system rises, the external valve switches from the larger to the smaller bore at a predetermined pressure level.
This allows the high-pressure side of the master cylinder to operate for the remainder of the brake actuation. Once pressurized the system continues to operate on the smaller bore without the external value switching in and out, allowing progressive braking.