Brakes

Brake System


General
The E38 ABS 5 or optional ASC+T 5 traction control system is identical in operation as introduced on the E34 (9-93). ASC+T 5 system operation information can be found in the E38 Features Handout.

The hydraulic circuits of either system use the Black and White hydraulic: circuit layout. This system differs from the previous dual diagonal system in the way the hydraulic circuits are split.

As shown, one master cylinder bore is connected to both front calipers and the other bore to the rear calipers.

E38 Black and White Hydraulic Layouts:












Master Cylinder

- Closed Loop Hydraulic Control












The ASC+T 5 is a closed loop hydraulic system. "Closed loop" refers to the fluid supply to the hydraulic unit when in regulation.

The closed loop system incorporates a central valve in the forward piston of the master cylinder. This valve allows the hydraulic pump to access the brake fluid directly through the master cylinder when in regulation. In comparison to an open loop system like the E36 TEVES Mark IV system the brake fluid is available to the hydraulic unit through hoses from the master cylinder

Vacuum Booster







A new compact vacuum booster mounted to the driver's side engine compartment bulk-head. The booster receives vacuum from a hose connected to a port at the crankcase ventilation valve located on the back of the intake manifold.

Front Brakes







The 11.9" ventilated rotors of the E32 have been upgraded to 12.8" (324mm) diameter X 30mm thick for the E38.

The large 60mm single piston floating calipers complete the E38 brake system.

Rear Brakes







The E38's 12.8" (324mm) diameter X 12mm thick solid rear rotor is also increased from the E32's 11.8" rotors.

The rear 40mm single piston, floating, cast caliper has also been increased in size from the E32's.