Brakes and Traction Control: Description and Operation

Brake System

The brake system has the following components:

- Brake master cylinder and fluid reservoir
- Cable/caliper actuated parking brake system
- Clevis pin
- Electric vacuum pump (hybrid vehicles)
- Fixed position brake pedal (non-hybrid vehicles)
- Fixed position brake pedal with integrated brake-by-wire system (hybrid vehicles)
- Four-wheel ABS
- Front and rear disc brake systems
- Vacuum-assisted power brake booster (non-hybrid vehicles)
- Vacuum-assisted active booster (hybrid vehicles)
- Red brake light indicator


Conventional Brake System (Non-Hybrid Vehicles)

The brake pedal is connected to the vacuum power brake booster, which is connected to the brake master cylinder. When the brake pedal is applied, brake fluid is pushed through the double-walled steel tubes and flexible hoses to the disc brake calipers. The brake fluid enters the disc brake calipers, forcing the caliper pistons and brake pads outward against the brake disc friction surfaces, slowing or stopping wheel rotation. When the brake pedal is released, brake fluid pressure is relieved, returning the disc brake systems to the unapplied position.

Regenerative Braking System (Hybrid Vehicles)

During braking, the regenerative brake system utilizes the electric motor portion of the hybrid electric power train as a generator to create electrical current. This recharges the High Voltage Traction Battery (HVTB) in combination with the vehicle's conventional friction brakes while slowing the vehicle. The amount of brake torque provided by the electric motor is dependent upon the state of charge of the HVTB. When the HVTB is almost fully charged, the amount of regenerative braking is limited to avoid overcharging, and the requested deceleration is produced by conventional friction braking alone.

For information on the following components:

- Front disc brakes, refer to Front Disc Brake Front Disc Brake
- Rear disc brakes, refer to Rear Disc Brake Rear Disc Brake
- Parking brake actuation, refer to Parking Brake and Actuation Description and Operation
- Hydraulic brake actuation, refer to Hydraulic Brake Actuation Description and Operation
- Vacuum-assisted power brake booster, refer to Power Brake Actuation Description and Operation
- ABS, refer to Vehicle Dynamic Systems Antilock Brakes / Traction Control Systems
- Vacuum-assisted active brake booster, refer to Vehicle Dynamic Systems Antilock Brakes / Traction Control Systems
- Electric vacuum pump, refer to Vehicle Dynamic Systems Antilock Brakes / Traction Control Systems