Brake Hydraulics
for your 1981 BMW 633CSi
The arrangement of brake system components that use fluid to transfer controlling pressure to the caliper is called the brake hydraulics. Without this transfer, your BMW 633CSi would be unable to reduce its speed or stop. These actions are important to both your safety on the road and that of other drivers.
A failing brake system is an accident waiting to happen, and you should never ignore early warning signs of malfunction. This might include the feeling of a spongy pedal (that is, the brake pedal compression is soft). Replacing parts immediately can prevent further BMW 633CSi damage. Keep your fluid levels high to avoid a problem, and bleed all air from the lines.