Chapter 8 Flashcards
List the components of a typical drum brake assembly.
drum, hub, brake shoes, backing plate, hydraulic wheel cylinder, springs, parking brake
Describe the function of a wheel cylinder.
converts hydraulic pressure to mechanical force
Describe brake gas fade.
hot gases get trapped under the shoes and acts as a lubricant
What are the major advantages to using drum brakes?
self energizing & servo action
Since duo-servo brakes supply more braking force than leading-trailing drum brakes, why would engineers use the leading-trailing design?
if duo-servo brakes are used in the rear wheels then the could overpower them and cause the back brakes to lock up
What determines the braking surface area of a drum brake?
What is the function of a self-adjuster?
use the movement of brake shoes to maintain proper clearance
What is a self-energizing brake?
creates its own mechanical leverage
What is the difference between the braking action of leading-trailing and duo-servo brakes?
A duo-servo brake is distinguished from a leading-trailing brake by a single anchor post at the top of the backing plate. The top of each shoe web has a semicircular notch, and the return springs hold the notches tightly against the anchor post.
How are the brake shoes returned to their released position when the brake pedal is released?
The mechanical servo returns the brake shoes
________ are the components that mount the friction material or linings that contact the drums.
brake shoes
The hydraulic and friction components are attached to the _______
backing plate
_________ operation is the action of a drum brake shoe when drum rotation increases the application force of the shoe by wedging it tightly against the drum.
self-energizing
The ________ is usually part of the parking brake strut that is mounted between the two shoes of leading-trailing brakes.
star wheel
A duo-servo brake is distinguished from a leading-trailing brake by a single anchor post at the _______ of the backing plate.
top
_________ brakes, also called partial-servo or non-servo brakes.
Duo-servo brakes commonly have self-adjusters operated by the ________ shoe.
secondary
Cam-type adjusters use cams with an ________ pin that fits in a slot on the shoes.
adjuster
Wheel cylinders convert _________ pressure from the master cylinder to ________ force that applies the brake shoes.
hydraulic, mechanical
The forward shoe of a duo-servo brake is called the ________ shoe.
primary
Technician A says that for the same brake pedal force, duo-servo brakes apply a greater braking force than leading-trailing-shoe brakes.
Technician B says that the servo action of the duo-servo brakes takes place only when the car is moving forward.
Who is correct?
a
Technician A says that the leading shoe lining receives the greatest wear on a leading-trailing shoe brake.
Technician B says that leading-trailing brakes are non-servo brakes.
Who is correct?
c
Technician A says that some leading-trailing-shoe brakes with an adjustable parking brake self-adjust when the service brakes are applied.
Technician B says that some brakes with an adjustable parking brake strut self-adjust when the parking brake is applied.
Who is correct?
b
Technician A says that on a duo-servo brake, the force applied by the drum to the primary shoe aids the force applied by the wheel cylinder.
Technician B says that on a leading-trailing brake, the force applied by the drum to the primary shoe opposes the force applied by the wheel cylinder.
Who is correct?
a
Two technicians are discussing automatic brake adjusters.
Technician A says that self-adjusting brakes were first used in 1947 by Studebaker.
Technician B says that self-adjusting brakes were used on all domestic drum brakes in 1963.
Who is correct?
c
Technician A says that rear brake drums are usually separate assemblies from the rear hubs.
Technician B says that Tinnerman nuts at the wheel studs hold the drum onto many rear hubs.
Who is correct?
While discussing a typical leading-trailing brake installation,
Technician A says the wheel cylinder is mounted at the top of the backing plate, and the cylinder pushrod or shoe links bear against the upper ends of the shoe webs.
Technician B says the lower end of each shoe bears against, or is held onto, an anchor block or anchor post toward the bottom of the backing plate.
Who is correct?
Technician A says that most self-adjusters are the same for both sides of the vehicle.
Technician B says that some technicians service one side of the vehicle at a time and use the other side as a reference while assembling drum brake assemblies.
Who is correct?
b
Technician A says on leading-trailing brakes, the lining on the leading and trailing shoes are usually the same length and positioned in the same location on each shoe.
Technician B says on duo-servo brake, however, the primary shoe lining is shorter than the secondary lining and may even have a different coefficient of friction.
Who is correct?
d
