Chapter 8 Flashcards
1.List the components of a typical drum brake assembly.
backing plate, brake drum, shoe, wheel cylinder, and various springs and pins.
2.Describe the function of a wheel cylinder.
Wheel cylinders convert hydraulic pressure from the master cylinder to mechanical force that applies the brake shoes.
3.Describe brake gas fade.
Gas fade is a condition that occurs under hard braking when hot gases and dust particles are trapped between the brake linings and the drum or rotor and build up pressure that acts against brake force
4.What are the major advantages to using drum brakes?
The major drum brake advantages are self-energizing and servo action, lack of noise, and efficient parking brake operation without complicated linkage.
5.Since duo-servo brakes supply more braking force than leading-trailing drum brakes, why would engineers use the leading-trailing design?
FWD automobiles generate up to 80 percent of their braking force on the front wheels. Overly powerful duo-servo brakes at the rear could easily cause the rear wheels to lock as weight shifts forward and the rear end becomes very light during braking
6.What determines the braking surface area of a drum brake?
The braking surface area of a drum is determined by the diameter and the depth (width) of the drum.
7.What is the function of a self-adjuster?
Brake adjustment compensates for lining wear and maintains correct clearance between
brake linings and the drum.
8.What is a self-energizing brake?
To add its own mechanical leverage to hydraulic force to help apply the brakes
9.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.
10.How are the brake shoes returned to their released position when the brake pedal is released?
Strong return springs retract the shoes when the brakes are released and hold them
against their anchors and the wheel cylinder pushrod.
. _______________ 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 engergizing
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.
leading-trailing
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.
hyrdraulic - mechanical
The forward shoe of a duo-servo brake is called the _______________shoe.
primary
Duo-servo brakes commonly have self-adjusters operated by the secondary shoe.
secondary
1.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 only
2.Technician A says that the leading shoe lining receives the greatest wear on a leading-trailing shoe brake. Technician B says that lead-ing-trailing brakes are non-servo brakes. Who is correct?
both
3.Te c h n i c i a n 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?
both
4.Te c h n i c i a n 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?
neither
5.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?
a only
6.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?
b only
7.While discussing a typical leading-trailing brake installation, Te c h n i c i a n 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?
both
8.Te c h n i c i a n A says that most self-adjusters are the same for both sides of the vehicle. TechnicianB 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 only
9.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?
both
10.Te c h n i c i a n A says that self-adjusters perform lining-to-drum adjustments without driver intervention.Technician B says that self-adjusting duo-servo brakes occur when the vehicle is moving forward and the brakes are applied. Who is correct?
b only
