Five free practice questions on drum brakes: content area B of the ASE A5 Brakes test, 5 of its 45 scored questions (11.1%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A brake drum's service information lists a maximum refinish diameter of 9.030 in.; the discard diameter cast in the drum is 9.060 in. The drum measures 9.018 in., and its deepest score is 0.010 in. deep, so the cleanup cut must remove that much metal from the braking surface. What should the technician do?
- Reuse it; 9.018 in. is under 9.030 in.
- Machine it; it will finish at 9.028 in.
- Machine it; 9.038 in. is under 9.060 in.
- Replace it; it would finish at 9.038 in.
Show the answer
D. Correct. Removing 0.010 in. from the surface all the way around adds twice that to the diameter: 9.018 + (2 x 0.010) = 9.038 in., which is over the 9.030 in. maximum refinish diameter. The gap between refinish and discard diameters is left for wear in service, so the drum is replaced.
Why not the others
A. The drum is under the 9.030 in. refinish limit now, but a drum scored 0.010 in. deep is not reused as is; the scoring wears new linings and reduces contact. Cleaning it up would take it to 9.038 in., over the 9.030 in. refinish limit, so the drum is replaced.
B. This adds the 0.010 in. score depth to the diameter once (9.018 + 0.010 = 9.028 in.), but the cut removes metal on both sides of the diameter, so the finished size is 9.018 + 0.020 = 9.038 in., over the 9.030 in. refinish limit. Replace the drum.
C. The arithmetic is right but the reference is wrong: 9.060 in. is the discard diameter, a wear limit for a drum in service. A machined drum must finish at or under the 9.030 in. refinish limit, and 9.038 in. does not, so it is replaced.
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When a brake drum is machined on a lathe, what is the purpose of the silencer band wrapped around the outside of the drum?
- To center the drum on the lathe's arbor shaft
- To damp the vibration that causes chatter
- To keep cutting heat from distorting the drum
- To balance the drum while the lathe turns it
Show the answer
B. Correct. A drum rings like a bell under the cutting bit, and that vibration leaves a rough, chattered finish. The band damps the vibration so the bit cuts a smooth, even surface.
Why not the others
A. Centering is done by the cones and adapters that clamp the drum on the arbor at its bearing races or center hole. The silencer band only damps vibration during the cut.
C. A lathe cut does not heat a drum enough to distort it, and the band is not a heat sink. It presses on the outside of the drum to damp the vibration that makes the bit chatter.
D. The band does not add or remove weight to balance the drum. It presses on the outside of the drum to damp the ringing vibration that causes chatter marks.
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Rear brake shoes have just been replaced with no hydraulic part opened, the drums and wheels are back on, and the lug nuts are torqued. What should the technician do before moving the vehicle?
- Back off each star wheel two notches
- Drive slowly so that the self-adjusters take up clearance
- Bleed both rear wheel cylinders again
- Pump the brake pedal until it is high and firm
Show the answer
D. Correct. Shoe service pushes the wheel cylinder pistons in and leaves running clearance, so the first pedal stroke can go far down. Pumping brings the shoes out to the drums and confirms a firm pedal before the vehicle moves.
Why not the others
A. Backing off the star wheels adds clearance and lowers the pedal further. The shoes are preadjusted to the drums, and the pedal is then pumped until it is high and firm.
B. The self-adjusters fine-tune clearance as the vehicle is driven and braked, but the vehicle must not be moved until pumping the pedal has given a high, firm pedal.
C. Bleeding removes air, and no hydraulic part was opened, so no air was let in. The low first pedal comes from the pistons and shoes being retracted, which pumping the pedal takes up.
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A brake drum is measured with a drum micrometer at the open edge of the braking surface and again at the inner edge, near the drum's closed face. What condition does a difference between those two readings show?
- Out-of-round wear
- Tapered wear
- Thickness variation
- Radial runout
Show the answer
B. Correct. Comparing the diameter at the open edge with the diameter at the inner edge shows whether the braking surface is tapered; a bell-mouthed drum is larger at the open edge. Taper reduces lining contact, so the drum is machined or replaced per the manufacturer's limits.
Why not the others
A. Out-of-round is found by comparing diameters measured at several points around the drum at the same depth. Readings at the open and inner edges show taper.
C. Thickness variation is a rotor measurement taken with a micrometer across the two braking faces. A drum's open-edge and inner-edge diameters show taper.
D. Radial runout is read with a dial indicator against the braking surface while the drum turns. Two diameters at different depths show taper.
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A technician is reassembling a drum brake with new shoes. Technician A says the shoe contact pads on the backing plate get a thin film of high-temperature brake lubricant. Technician B says the star wheel adjuster threads are cleaned and lubricated so the adjuster can turn. Who is right?
- A only
- B only
- Both A and B
- Neither A nor B
Show the answer
C. Correct. Technician A is right: the shoes slide on the backing plate contact pads, and a thin film of high-temperature brake lubricant keeps them from sticking and squeaking. Technician B is right: the adjuster screw must turn freely for the self-adjuster to work, so its threads are cleaned and lubricated; keep lubricant off the linings.
Why not the others
A. Not A only. Technician A is right: the shoes slide on the contact pads and need a thin film of high-temperature brake lubricant to move without sticking or squeaking. Technician B is right as well: a dry or corroded adjuster screw will not turn, and the self-adjuster cannot take up lining wear.
B. Not B only. Technician B is right that the adjuster threads are cleaned and lubricated so the screw turns freely. Technician A is right too: the shoe contact pads on the backing plate get a thin film of high-temperature brake lubricant so the shoes slide.
D. Both technicians are right. Technician A describes lubricating the backing plate contact pads, and Technician B describes cleaning and lubricating the adjuster threads; both are part of reassembling a drum brake.
02Answer key
| Question | Answer |
|---|---|
| Q1 | D |
| Q2 | B |
| Q3 | D |
| Q4 | B |
| Q5 | C |
03What area B covers
This content area covers drum brakes from the wheel cylinder out to the drum: shoes, springs, self-adjusters and other hardware, wheel cylinders, measuring and machining drums, and preadjusting the shoes and parking brake before the drum goes back on. It also takes in the wheel bearings that sit in many drum hubs, from bearing noise to repacking and adjustment.
The ASE test specification calls this content area “Drum Brake Diagnosis and Repair”. It carries 5 of the 45 scored questions, 11.1% of the test.
- Trace pulls, drag and low pedal to drum faults
- Measure drums and decide to machine or replace
- Machine drums to the manufacturer's procedure
- Clean and inspect shoes, springs and self-adjusters
- Lubricate backing plate pads and adjuster threads
- Inspect, replace and bleed wheel cylinders
- Preadjust shoes and parking brake before fitting drums
- Diagnose, repack and adjust wheel bearings and seals
04What the questions turn on
Refinish limit versus discard
A drum's maximum refinish diameter is smaller than its discard diameter, which leaves room for wear in service. A cut removes metal all the way around, so the diameter grows by twice the depth of the cut. Past the refinish limit, the drum is replaced.
Parts made for one side
Star wheel adjusters and wheel cylinders are often made for one side. Swapped adjusters back the shoes off with each stroke, so the pedal keeps dropping. A cylinder from the other side mounts with its bleeder low and traps air above it.
Heat-blued springs and soaked linings
Return springs discolored blue by heat are weakened and are replaced, because a weak spring can let the shoes drag. Linings soaked with brake fluid cannot be cleaned, and shoes are replaced in axle sets so both brakes grip alike.
Finding a rear pulsation
The parking brake applies only the rear shoes. If gently applying it reproduces the pulsation, the rear drums are the source. An out-of-round drum changes the shoe force once every turn, so it is measured at several points around the surface.
05The other content areas
The A5 test has four content areas. Each has its own page of free questions:
The ASE A5 Brakes practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.