Lexus SC300 / Lexus SC400. Service manual - part 245

BRAKE SYSTEM

BR–1

GENERAL DESCRIPTION

BR03E–06

1. 

Care must be taken to replace each part properly as it could affect the performance of the brake
system and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.

2. 

It is very important to keep parts and the area clean when repairing the brake system.

3. 

If the vehicle is equipped with a mobile communication system, refer to the precaution in the IN
section.

DESCRIPTION

BR03F–03

The service brakes consist of a foot brake which changes rotational energy to thermal energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from moving while it is parked.

OPERATION

FOOT BRAKE

BR03G–06

When the brake pedal is depressed, a vacuum builds up in the booster which amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylinder, and acts to press the
brake pads against the rotating discs. The resulting friction converts the rotational energy to thermal ener-
gy, stopping the vehicle.

BR–2

–

BRAKE SYSTEM

OPERATION

GENERAL DESCRIPTION

BR03E–06

1. 

Care must be taken to replace each part properly as it could affect the performance of the brake
system and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.

2. 

It is very important to keep parts and the area clean when repairing the brake system.

3. 

If the vehicle is equipped with a mobile communication system, refer to the precaution in the IN
section.

DESCRIPTION

BR03F–03

The service brakes consist of a foot brake which changes rotational energy to thermal energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from moving while it is parked.

OPERATION

FOOT BRAKE

BR03G–06

When the brake pedal is depressed, a vacuum builds up in the booster which amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylinder, and acts to press the
brake pads against the rotating discs. The resulting friction converts the rotational energy to thermal ener-
gy, stopping the vehicle.

BR–2

–

BRAKE SYSTEM

OPERATION

PARKING BRAKE

BR03H–04

When the parking brake lever is pulled up, the parking brake shoe lever is pulled via the parking brake wire.
This causes the shoe strut to push the front shoe, which expands and is pressed against the disc. If the
parking brake lever continues to be pulled up, the contact point of the parking brake shoe lever and shoe
strut then becomes the fulcrum so that the parking brake shoe lever causes the rear shoe to expand. This
results in the disc being locked by the front shoe and rear shoe.

–

BRAKE SYSTEM

OPERATION

BR–3