B - Hydraulic Brake System (Drum and Disc) Flashcards
Brake drums used on medium duty trucks are usually made from the following material:
Cast iron or centrefuse.
List three functions of the drum brake backing plate.
Mounting points for: the anchor(s); the wheel cylinder(s). Inspection holes for lining-to-drum clearance. Service access holes for brake adjustment; brake bleeder screw(s).
Brake shoe assemblies could be classed as servo acting or non-servo acting. Explain the differences.
Servo action occurs when one shoe is positioned so it can move the other shoe during brake application. Non-servo action both brake shoes act independently of each other.
Explain the purpose of brake shoe return springs.
Returns brake shoes to release position. Prevents brake drag. Indirectly forces brake fluid back to the master cylinder.
List two functions of a disc brake calliper.
Provides cylinder bore(s) for calliper piston(s) and holds inner and outside disc brake pads.
Disc brake pad lining material is generally described as:
Non-asbestos organic (NAO) and semi-metallic.
Explain the main purpose of vented disc brake rotors.
Vents provide increased cooling air flow during vehicle operation. This helps to dissipate rotor heat faster.
True or False: Disc brakes have both servo and self-energizing action.
False; Discs brakes have neither. They rely on a clamping force.
Explain why master cylinders generally have two separate reservoirs.
Safety is the prime reason. Two independent systems exist. Failure in one system does not affect the other system.
The master cylinder has two small ports leading into the cylinder bore from each reservoir. Name and explain the purpose(s) of the small port.
Compensating port. Allows brake fluid into the cylinder bore as the brakes are being released. Allows heated brake fluid to expand into the reservoir to prevent brake drag. Allows cooled fluid to return to the cylinder bore.
True or False: A horizontally mounted master cylinder has a primary and secondary piston. The primary piston is the first one activated by the brake pedal pushrod.
True.
Explain how the secondary piston in the master cylinder is moved during normal braking operation.
The primary piston moves; the compensating port is closed; brake fluid is trapped between the primary and secondary piston; the trapped fluid moves the secondary piston; the trapped fluid moves the secondary piston.
True or False: Double flares and ISO flares used on steel brake tubing.
True.
Steel tubing with double flares can be used with fittings that are designed for ISO flares.
False; Double flares and fittings must never be interchanged with ISO flares and fittings.
Explain why flexible hoses are used as brake lines.
To prevent line breakage as components move.