Brake Systems Lesson Test (40 Questions)

Answer: B

Correct answer: Heat in the pads, shoes, rotors and drums. Stopping means removing kinetic energy. Friction brakes do this by rubbing friction material against a part that turns with the wheel, so the energy leaves as heat in the brake parts and then passes into the air.

• A: Brake fluid only transmits force; it does not store the car's energy.
• B (correct): Friction brakes rub a fixed lining against a turning part, turning motion into heat.
• C: That describes regenerative braking in hybrids and EVs, not ordinary friction brakes.
• D: The booster only helps the driver push the pedal; it does not absorb the car's energy.

Answer: D

Correct answer: The master cylinder. The order is pedal, booster, master cylinder, then lines. The pushrod drives the master-cylinder pistons, seals close the reservoir ports, and the trapped fluid is pressurized for the first time there.

• A: The caliper receives pressure at the wheel; it does not create it.
• B: The reservoir only stores spare fluid at low pressure.
• C: The booster adds push to the pushrod, but the pressure is made in the cylinder after it.
• D (correct): Its pistons trap fluid and force it into the lines, which is where hydraulic pressure begins.

Answer: D

Correct answer: Wheel cylinder. Hydraulic pressure reaches the wheel cylinder, whose pistons push the shoes outward onto the drum. Return springs then pull the shoes back when the pedal is released.

• A: A caliper clamps pads on a disc brake rotor; it is not found in a plain drum brake.
• B: Return springs pull the shoes back toward center after pressure drops.
• C: The backing plate is the fixed mount for the parts; it does not move the shoes.
• D (correct): Its two pistons, one at each end, push the shoes apart when pressure arrives.

Answer: C

Correct answer: The wheel moves with the suspension and, at the front, with steering. Steel tubing is used on the body because it does not swell under pressure. At each wheel the path must bend as the suspension moves and the front wheels steer, so a flexible reinforced hose is used there.

• A: Most of the system is steel tubing, so steel and brake fluid are compatible.
• B: A hose carries pressure; it cannot increase it.
• C (correct): A rigid tube could not follow the wheel's up-and-down and steering motion without breaking.
• D: Air must be removed by bleeding; a hose does not vent it.

Answer: A

Correct answer: It is nearly incompressible. Pascal's principle works because the confined fluid barely compresses. Pedal motion becomes pressure that is passed equally to every piston in the circuit instead of being lost squeezing the fluid.

• A (correct): Because the liquid barely squeezes, pushing the piston raises the pressure throughout the circuit.
• B: Fluid must flow well, even in cold weather, to reach the wheels.
• C: Compressible air or vapor is a fault that causes a spongy pedal.
• D: Brake fluid needs a high boiling point; low boiling causes vapor and a soft pedal.

Answer: D

Correct answer: The anti-lock system found a fault, but normal braking usually remains. The amber ABS lamp means the anti-lock system has detected a fault and may be switched off. Normal braking typically remains without anti-lock help, but the fault should be checked.

• A: An applied parking brake lights the red brake warning, not the amber ABS lamp.
• B: The ABS lamp does not mean total brake loss; the base hydraulic brakes normally remain.
• C: Worn pads usually announce themselves with a squeal or a separate wear lamp, not the amber ABS lamp.
• D (correct): The amber lamp reports an ABS fault; base brakes typically still work, just without anti-lock help.

Answer: A

Correct answer: The pad lining is thin and service is due. Wear indicators are small metal tabs on the pads. When the lining gets thin they rub the rotor and squeal, telling the driver to schedule brake service before metal-to-metal grinding begins.

• A (correct): The metal tab touches the rotor when the lining wears down, as an audible warning.
• B: Lost assist gives a hard pedal, not a squealing noise.
• C: ABS works only in hard stops near wheel lock and is felt as pedal buzzing.
• D: Moisture in the fluid causes vapor and a soft pedal, not a squeal from the pad.

Answer: C

Correct answer: The driver keeps the ability to steer. A locked, skidding tire cannot make useful side force, so steering is lost. ABS reduces, holds and reapplies pressure many times per second to keep each wheel rolling, which preserves steering control.

• A: The driver must still press firmly; ABS only adjusts the pressure at each wheel.
• B: ABS does not guarantee a shorter stop; on gravel or deep snow a locked wheel can stop shorter.
• C (correct): Keeping the wheels rolling near peak grip lets the tires still produce side force for steering.
• D: ABS cannot raise the tire-to-road friction limit.

Answer: D

Correct answer: Air was left in the hydraulic system. Brake fluid is nearly incompressible, but air is not. If air enters during service and is not fully bled out, the bubbles compress and the pedal feels soft and travels farther, so the car should go back for proper bleeding and a leak check.

• A: A failed booster gives a hard pedal that needs more force, not a soft, long pedal.
• B: Uneven rotors cause pulsing during light stops, not a soft, sinking pedal.
• C: Friction fade leaves a firm pedal with weaker stopping, not a spongy pedal right after service.
• D (correct): Opening a line can let air in, and air compresses, so part of the pedal stroke is wasted squeezing bubbles.

Answer: C

Correct answer: 1,620 N. Find the pressure, then multiply by the output area.

N/cm²

• A: This multiplies 360 by 18 without first dividing by the master-piston area.
• B: This inverts the area ratio, making the larger piston get less force.
• C (correct): Pressure is 360 ÷ 4 = 90 N/cm², and 90 × 18 = 1,620 N.
• D: This is the pressure in N/cm², not the force on the caliper piston.

Answer: A

Correct answer: 900 N.

The pedal moves five times farther than the pushrod in exchange.

• A (correct): The lever ratio is 30 ÷ 6 = 5, so 180 × 5 = 900 N.
• B: This multiplies 180 by 30, the long distance, instead of by the ratio.
• C: This multiplies 180 by 6, the short distance, instead of by the ratio.
• D: This divides by the lever ratio instead of multiplying, which would make the pedal reduce force.

Answer: B

Correct answer: Absorbed water lowered the fluid's boiling point, so vapor formed. Glycol-based fluid is hygroscopic, so old fluid holds water that lowers its boiling point. Hot brakes boil it, the vapor bubbles compress, and the pedal turns soft. This is why makers set fluid-change intervals.

• A: Friction fade keeps the pedal firm; a soft, sinking pedal points to the hydraulics.
• B (correct): Glycol fluid takes in moisture over time; hot brakes can then boil it, and vapor compresses.
• C: Heat does not block the lines; the problem is vapor bubbles that compress.
• D: Lost assist makes the pedal hard, not soft.

Answer: D

Correct answer: A leaking vacuum hose to the booster. A hard pedal with weak stopping means the booster's help is gone. A leaking vacuum hose, failed check valve, torn diaphragm or no engine vacuum can cause it. Soft pedals point to air, vapor or leaks instead.

• A: Air causes a soft, spongy pedal that travels farther, not a hard one.
• B: A leak lets the pedal sink lower; it does not make it hard.
• C: A sensor fault lights the amber ABS lamp but leaves pedal effort normal.
• D (correct): Without vacuum the booster cannot help, so the brakes still work but need much more leg force.

Answer: C

Correct answer: Check the fluid level and have the hydraulics inspected. The red lamp means parking brake on, low fluid or a hydraulic problem. Once the parking brake is ruled out, check the fluid level and treat it as a real hydraulic issue until a technician proves otherwise.

• A: A leak can worsen without warning, so a red lamp should never be ignored.
• B: Topping up hides the cause; a low level points to a leak or worn linings that needs checking now, not at the next service.
• C (correct): With the parking brake ruled out, low fluid or a hydraulic fault is the likely cause.
• D: Sensor faults usually light the amber ABS lamp, not the red brake lamp, so replacing sensors misses the likely cause.

Answer: D

Correct answer: Uneven rotor thickness or pad deposits. Pulsing in light, ordinary stops points to the rotor, often called a warped rotor, or an out-of-round drum. ABS pulsing is felt only in hard stops when a wheel nears lock.

• A: ABS pulsing happens only in hard stops near wheel lock, not every gentle stop.
• B: Air gives a spongy, long pedal rather than a rhythmic pulse.
• C: Lost assist makes the pedal hard; it does not cause pulsing.
• D (correct): The pads ride over high and low spots, so pressure rises and falls in light stops.

Answer: A

Correct answer: Use only the fluid type named on the cap or in the manual. DOT 3, 4 and 5.1 are glycol-based, while DOT 5 is silicone-based. They should not be mixed, so the owner should use the fluid named on the reservoir cap or in the owner's manual, from a sealed container.

• A (correct): DOT 5 is silicone-based and should not be mixed with glycol DOT 3; seals and ABS are built for one type.
• B: Silicone and glycol fluids do not mix well and can cause poor performance and seal problems.
• C: DOT numbers are not a simple ranking; DOT 5 is a different chemistry.
• D: DOT ratings are not freely interchangeable.

Answer: A

Correct answer: Braking shifts load forward, giving the front tires more grip. During deceleration load moves toward the front axle; the nose dips and the rear rises. The front tires gain grip, so front brakes are made larger and do well over half the work, while a proportioning valve or electronic distribution limits rear pressure.

• A (correct): With more weight on the front tires they can pass more brake force to the road.
• B: Engine location does not cool the brakes; the reason is load transfer during braking.
• C: Rear brakes do share the service braking, just a smaller portion.
• D: Many cars use the same tire size on both axles, yet front brakes still do more work.

Answer: B

Correct answer: Friction fade from overheated pads and rotors. A firm pedal shows the hydraulics are still building pressure. Continuous braking let the pads and rotors heat faster than they could cool, and hot friction material grips poorly. That is friction fade; a lower gear and brief, firm applications help prevent it.

• A: A failed circuit makes the pedal travel farther, not stay firm and normal.
• B (correct): Very hot friction material grips less, so the car slows less even though the pedal stays firm.
• C: Air would make the pedal soft and spongy, not firm.
• D: ABS shutdown does not reduce normal braking power on a firm pedal.

Answer: D

Correct answer: Press firmly, hold the pedal down and steer around the hazard. With ABS, the driver presses firmly and keeps the pedal down. The system modulates pressure many times per second, and the vibrating pedal and noise are normal. The driver looks and steers toward a safe path.

• A: Vibration and buzzing underfoot are normal signs that ABS is working, so the driver should keep pressing.
• B: Pumping interrupts ABS, which already cycles the pressure much faster than a person can to keep the wheels from locking.
• C: Light pressure wastes stopping ability in an emergency.
• D (correct): ABS pulses the brakes itself, so steady firm pressure plus steering gives the best result.

Answer: A

Correct answer: Energy quadruples. (2v)²=4v² at constant mass.

• A (correct): Correct: (2v)²=4v² at constant mass.
• B: This answer ignores that vehicle kinetic energy scales with the square of speed.
• C: Speed is part of the kinetic-energy calculation.
• D: Halving requires reduced speed, not doubling.

Answer: D

Correct answer: 600 kPa. One square meter is 10,000 cm², so 1 N/cm² = 10,000 Pa = 10 kPa. Then 60 N/cm² × 10 = 600 kPa, which is also 6 bar.

• A: This multiplies by 100 instead of 10.
• B: This divides by 10 instead of multiplying.
• C: This assumes 1 N/cm² equals 1 kPa, skipping the area conversion.
• D (correct): Since 1 N/cm² equals 10 kPa, 60 × 10 = 600 kPa.

Answer: D

Correct answer: 2,250 N. Area grows with the square of diameter, so the force ratio is

The output force is

The factor of π/4 cancels in the ratio.

• A: This divides by 9, which would make the larger piston produce less force.
• B: This uses the diameter ratio of 3 without squaring it.
• C: This multiplies 250 by the caliper diameter of 6.
• D (correct): The force ratio is (6/2)² = 9, so 250 × 9 = 2,250 N.

Answer: C

Correct answer: 320,000 J.

All of that energy must leave as heat in the brakes.

• A: This uses mass times speed, which is momentum, not energy.
• B: This uses half of mass times speed and forgets to square the speed.
• C (correct): $\frac{1}{2}\times 1600\times 20^2=320,000$ J.
• D: This squares the speed but leaves out the one-half.

Answer: C

Correct answer: 8,400 N. Newton's second law gives

That force comes from the grip between the tires and the road.

• A: This divides mass by deceleration instead of multiplying.
• B: This adds mass and deceleration instead of multiplying them.
• C (correct): $F=ma=1400\times 6=8400$ N.
• D: This takes half of the correct product, as if using the energy formula.

Answer: A

Correct answer: 40 m. Use the constant-deceleration stopping formula.

• A (correct): d = v² ÷ (2a) = 400 ÷ 10 = 40 m.
• B: This divides speed by deceleration, which gives a time in seconds, not a distance.
• C: This divides v² by a only and forgets the 2 in the denominator.
• D: This divides v by 2a without squaring the speed.

Answer: B

Correct answer: Wheel cylinder and brake shoes. Disc brakes use a caliper, pads and a rotor. Drum brakes use a wheel cylinder, shoes, a drum and return springs. Only the wheel cylinder and shoes come from the same brake type.

• A: Pads are applied by a caliper on a disc brake, not by a wheel cylinder.
• B (correct): Both belong to a drum brake: the wheel cylinder pushes the shoes outward against the drum.
• C: Pads clamp the faces of a rotor; shoes press on the inside of a drum.
• D: Calipers apply pads in disc brakes; shoes belong to drum brakes.

Answer: A

Correct answer: Left front and right rear. In a diagonal split, each circuit serves one front wheel and the opposite rear wheel. The right front pairs with the left rear, so the remaining circuit is the left front and right rear. The pedal travels farther and stopping takes longer, but partial braking remains.

• A (correct): The burst empties the circuit for the right front and its diagonal partner, the left rear.
• B: The left rear shares the failed circuit with the right front, so both rears cannot brake.
• C: A dual-circuit system keeps one circuit working when the other leaks.
• D: The right front is on the failed circuit, so the two front wheels cannot both brake.

Answer: C

Correct answer: Traction control. ABS prevents lock while braking, while traction control prevents spin while accelerating. Both share the wheel-speed sensors and hydraulic modulator, but they solve different problems.

• A: The booster only reduces pedal effort for the driver.
• B: ABS manages wheel lock during braking, not spin during acceleration.
• C (correct): Traction control manages spin during acceleration using the same sensors and modulator as ABS.
• D: A proportioning valve limits rear brake pressure during braking.

Answer: B

Correct answer: 90 m. Reaction distance:

Braking distance:

Total:

• A: This adds reaction distance correctly but forgets the 2 in the braking formula.
• B (correct): Reaction distance is 30 m and braking distance is 900 ÷ 15 = 60 m, for 90 m in all.
• C: This is only the braking distance and leaves out the 30 m covered during reaction time.
• D: This divides 900 by 7.5, forgetting the 2 in the formula, and also leaves out reaction distance.

Answer: C

Correct answer: Caliper pistons sit farther out as the pads wear. As pads wear, the caliper pistons move outward and hold more fluid, so a slow drop can be normal. A sudden drop or a level below MIN would instead point to a leak that needs prompt inspection.

• A: Reservoir level shows stored fluid, not system pressure.
• B: Fluid does not evaporate away in normal use; boiling causes a soft pedal.
• C (correct): More fluid stays in the calipers as the pads thin, so the reservoir level falls slowly.
• D: A vacuum booster works with air pressure and does not use brake fluid.

Answer: B

Correct answer: 3,600 kPa. The pedal lever multiplies the foot force:

N at the pushrod. Pressure is force over area,

N/cm². Since 1 N/cm² equals 10 kPa, the pressure is 3,600 kPa.

• A: This skips the pedal lever, using 180 N directly: 180 ÷ 2.5 = 72 N/cm², or 720 kPa.
• B (correct): The pushrod force is 180 × 5 = 900 N; 900 ÷ 2.5 = 360 N/cm², and 360 × 10 = 3,600 kPa.
• C: This converts with a factor of 100 instead of 10 kPa per N/cm².
• D: This finds 360 N/cm² but forgets that 1 N/cm² equals 10 kPa.

Answer: A

Correct answer: A right front caliper piston or guide pin that is sticking applied. One wheel running much hotter than the others means that brake is dragging. A sticking caliper piston or seized guide pin at the right front holds the pad on the rotor, causing the heat, the smell, and a pull toward the right. A weak left brake could also pull right, but it would not explain the hot right wheel.

• A (correct): A caliper that will not release keeps the pad on the rotor, heating that wheel and making it brake harder, so the car pulls toward it.
• B: Air causes a spongy pedal for all wheels; it does not overheat one wheel or cause a pull.
• C: This could cause a pull to the right, but it would not make the right front wheel run hot.
• D: A failed booster gives a hard pedal; it does not heat a single wheel or pull the car to one side.

Answer: C

Correct answer: 2,000 N. Lever:

N at the pushrod.

Pressure:

N/cm².

Caliper force:

• A: This stops at the pushrod force, or skips the pedal lever and applies only the area ratio.
• B: This applies the 4:1 pedal ratio twice.
• C (correct): Pushrod force is 500 N, pressure is 500 ÷ 2.5 = 200 N/cm², and 200 × 10 = 2,000 N.
• D: This is the line pressure in N/cm², not a force.

Answer: B

Correct answer: 5 times. Kinetic energy is proportional to mass and to speed squared.

• A: This squares the mass ratio as well as the speed ratio, but energy is proportional to mass.
• B (correct): The mass ratio is 1.25 and the speed ratio squared is 4, so 1.25 × 4 = 5.
• C: This accounts for the doubled speed but ignores the added load.
• D: This scales energy in a straight line with speed (1.25 × 2) instead of with speed squared.

Answer: C

Correct answer: 28 m. Use

for each surface.

Dry:

Wet:

The wet stop is

m longer, because water lowers the grip ABS has to work with.

• A: This forgets the 2 in the formula for both stops, doubling the difference.
• B: ABS keeps steering control but cannot raise tire grip, so the wet stop is still longer.
• C (correct): Dry: 576 ÷ 16 = 36 m. Wet: 576 ÷ 9 = 64 m. The difference is 28 m.
• D: This is the total wet braking distance, not how much longer it is.

Answer: B

Correct answer: Unequal front braking, such as a sticking caliper piston on one side. A pull only while braking means the two wheels on one axle are not doing equal work. Because the pedal is firm and normal, hydraulic air or leaks are unlikely, and because coasting is straight, alignment and tires are less likely. A sticking caliper piston, contaminated pad or collapsed hose on one side fits best.

• A: An alignment fault such as uneven camber would usually make the car pull while coasting too, not only during braking.
• B (correct): Only braking causes the pull, and a firm pedal rules out air or leaks, so one front brake is working harder or weaker.
• C: Lost assist makes the pedal hard and affects all wheels equally, so a leaking booster hose would not cause a pull.
• D: Air makes the pedal soft and spongy, which does not match the firm pedal.

Answer: D

Correct answer: 50 kJ and 200 kJ.

• A: These do not follow E=½mv² at the stated mass.
• B: Omitting the one-half factor would give 100 kJ and 400 kJ; these values also scale linearly with speed instead of with v².
• C: This treats kinetic energy as linear in speed.
• D (correct): Correct: 0.5×1000×100=50 kJ and 0.5×1000×400=200 kJ.

Answer: B

Correct answer: The friction brakes will handle more of the slowing. Regenerative braking stores energy in the battery. When the battery is already full there is little room for that energy, so the controller relies more on the friction brakes. That is one reason EVs always keep a hydraulic friction system that needs regular inspection.

• A: The battery cannot be charged beyond full, which is exactly why regeneration is reduced.
• B (correct): A full battery cannot accept much regenerated energy, so the controller blends in more friction braking.
• C: The hydraulic friction system is always available, whatever the battery charge.
• D: Regeneration is limited when the battery is full, so it cannot do all the work.

Answer: A

Correct answer: Fitting a larger-diameter rotor with the same pads. Clamping force creates a friction drag at the rotor's rubbing surface, and torque equals that drag times its distance from the axle. A larger rotor diameter moves the drag outward, and higher-friction pads would also help, so the same clamping force gives more torque.

• A (correct): The friction drag then acts farther from the axle, so the same clamping force makes more torque.
• B: Moving the rubbing surface closer to the axle reduces torque.
• C: Lower friction makes less drag force for the same clamping force.
• D: Reservoir level stores spare fluid and does not raise pressure or torque.

Answer: B

Correct answer: An electric actuator can apply a holding brake without manual cable leverage. Electric parking brakes replace the hand lever and cable with a switch that commands an electric motor, often mounted on a rear caliper, to clamp the brake and hold the vehicle. The service brakes used while driving remain hydraulic and are applied with the pedal. Because designs differ, some still use a motor that pulls a cable, so it is safest not to assume one layout. Its job is holding a stopped vehicle, not replacing normal braking.

• A: Incorrect: Service braking is still a separate hydraulic function used for normal stops while driving.
• B (correct): Correct: The holding action may be motor-driven; design varies.
• C: Parking brakes restrain wheel movement, not reverse engine rotation.
• D: Incorrect: Some designs use actuator motors at the wheels instead of a driver-pulled cable.

Answer: B

Correct answer: It reduces the leg effort needed to brake. The booster sits between the pedal and the master cylinder and multiplies the driver's effort, often using engine vacuum acting on a large diaphragm. It lowers the foot force needed but does not create braking by itself.

• A: Spare fluid is held in the reservoir on top of the master cylinder, not in the booster.
• B (correct): The booster adds push to the pushrod so the driver needs less foot force for the same braking.
• C: The booster only assists the driver's push; it does not apply the brakes on its own.
• D: Adjusting pressure at a locking wheel is the job of the ABS modulator.

Answer: D

In a floating caliper, fluid pressure moves the single piston out against the inner pad. When that pad meets the rotor, the caliper body slides on its guide pins in the opposite direction and draws the outer pad onto the other face, so both pads clamp the rotor.

• A: The rotor is bolted to the hub and turns with the wheel; it does not shift sideways to meet a pad.
• B: Wheel cylinders belong to drum brakes and push shoes, not disc pads.
• C: Return springs pull drum shoes away from the drum when pressure drops; they do not apply disc pads.
• D (correct): Once the inner pad meets the rotor, the reaction force shifts the floating body inward so the outer pad is squeezed too.

Answer: B

Correct answer: 3,750 N. First apply the lever: 150 N x 4 = 600 N at the pushrod. Piston area scales with diameter squared, so the force ratio is

• A: This uses the area ratio but skips the 4:1 pedal lever, starting from 150 N instead of 600 N.
• B (correct): Lever force 150 x 4 = 600 N, then the area ratio (5/2) squared = 6.25 gives 600 x 6.25 = 3,750 N.
• C: This multiplies by the diameter ratio 2.5 instead of squaring it; area grows with diameter squared.
• D: This divides the 600 N pushrod force by 2.5, which makes the larger caliper piston give less force, the wrong direction.

Answer: C

Correct answer: 72 m. From

with the same deceleration the distance is proportional to $v^2$. The speed ratio is

so the distance ratio is

and 32 m x 2.25 = 72 m.

• A: This scales distance in a straight line with speed (32 x 1.5), but distance depends on speed squared.
• B: This adds the 8 m/s speed increase to the distance, which mixes unrelated units.
• C (correct): The speed ratio is 24/16 = 1.5, and braking distance grows with the square: 32 x 2.25 = 72 m.
• D: This cubes the speed ratio (32 x 3.375); braking distance grows with the square of speed, not the cube.

Answer: A

Correct answer: Rotor. Friction brakes rub a stationary part against a part that turns with the wheel. In a disc brake the turning part is the rotor, while the caliper and its pads stay fixed and clamp it.

• A (correct): The rotor, or disc, is fastened to the hub and spins with the wheel while the pads squeeze it.
• B: The caliper straddles the rotor and holds the pistons, but it does not rotate with the wheel.
• C: Pads are held by the caliper and stay stationary while rubbing on the turning rotor.
• D: A backing plate is the fixed mounting for the shoes in a drum brake, and it does not turn.

Answer: B

Correct answer: The modulator briefly reduces, holds and reapplies pressure at that wheel. Wheel-speed sensors report each wheel's speed to the controller. When one wheel slows far faster than the car, the controller commands the hydraulic modulator to cut, hold and reapply pressure at that wheel rapidly, so the tire keeps rolling and the driver can still steer.

• A: ABS acts on the circuit of the affected wheel and keeps braking the car; it does not cut all braking.
• B (correct): ABS cycles pressure to the wheel that is about to lock many times per second, keeping it rolling near peak grip.
• C: Adding pressure to a wheel that is already near lock would make it lock and skid.
• D: The amber lamp signals a detected fault; a wheel nearing lock is the normal situation ABS is built to handle.

Answer: B

Correct answer: Electronic stability control. The clues are steering angle, yaw rate and sideways acceleration, used to keep the car pointed where the driver steers. That describes electronic stability control, which shares wheel-speed sensors and the modulator with ABS and traction control but solves a different problem.

• A: ABS prevents wheel lock during braking; it does not use yaw rate to correct a skid in a curve.
• B (correct): Stability control compares where the driver is steering with how the car is actually turning and brakes individual wheels to correct it.
• C: Traction control limits wheel spin during acceleration by braking the spinning wheel or cutting engine power.
• D: A proportioning valve limits rear brake pressure during stops; it has no steering or yaw sensors.

Answer: C

Correct answer: To serve as the parking brake, applied mechanically by cable. Some rear disc brakes hide a small drum inside the rotor hat just for parking. The caliper and rotor are the hydraulic service brake, while the cable-applied shoes in the small drum hold the stopped vehicle in place.

• A: The hydraulic caliper on the outer rotor is the service brake; the inner drum is not used to slow a moving truck.
• B: Cooling vanes are part of a ventilated rotor; the small drum is a holding brake, not a cooling device.
• C (correct): The inner drum and small shoes only hold the parked vehicle; the outer rotor and caliper do the service braking.
• D: Backup braking comes from the second hydraulic circuit of the tandem master cylinder, not from the parking drum.

Answer: A

Correct answer: Engine braking holds back the truck, so the service brakes are used less and stay cooler. Engine braking comes from the engine's internal resistance when the driver lifts off the throttle in gear, and a lower gear makes it stronger. Because it carries part of the slowing load on a long descent, the pads and rotors heat up less and are less likely to fade.

• A (correct): A lower gear increases engine braking, sharing the work and leaving the friction brakes cooler and less prone to fade.
• B: Gear choice does not change hydraulic line pressure or clamping force; that comes from the pedal, booster and master cylinder.
• C: ABS acts only when a wheel nears lock; gear choice is about sharing the slowing work, not triggering ABS.
• D: Engine braking adds to the service brakes but does not replace them; even on a steep grade the driver still brakes when needed.

Answer: D

Correct answer: 45 bar. Pressure is force over area: 1,800 N ÷ 4 cm² = 450 N/cm². Since 1 N/cm² equals 10 kPa, that is 4,500 kPa. One bar is 100 kPa, so

bar.

• A: This divides by 100 directly from N/cm², skipping the step that 1 N/cm² equals 10 kPa.
• B: This treats 1 N/cm² as equal to 1 bar, but 1 bar is 10 N/cm².
• C: This is the value in kilopascals; it still has to be divided by 100 to get bar.
• D (correct): 1,800 ÷ 4 = 450 N/cm², which is 4,500 kPa, and 4,500 ÷ 100 = 45 bar.

Answer: A

Correct answer: 6 m/s². Newton's second law says F = ma, so

• A (correct): From F = ma, a = 7,200 N ÷ 1,200 kg = 6 m/s².
• B: This slips a decimal place; 7,200 divided by 1,200 is 6, not 0.6.
• C: This divides mass by force (1,200 ÷ 7,200) instead of force by mass.
• D: This is ten times too large; check the division 7,200 ÷ 1,200 again.

Answer: D

Correct answer: 5,400 N. The brakes must do work equal to the kinetic energy:

Since W = F x d,

Check:

• A: This leaves out the one-half in the kinetic energy formula, doubling the energy and the force.
• B: This uses m x v ÷ d without squaring the speed or using the energy formula.
• C: This applies the one-half but forgets to square the speed, so the energy is far too small.
• D (correct): KE = 0.5 x 1,500 x 18² = 243,000 J, and dividing by 45 m gives 5,400 N.

Answer: A

A tandem master cylinder feeds two separate circuits, so one leak still leaves partial braking. During a stop, load transfers to the front axle, which is why front brakes are larger and do most of the work. With only the rear circuit left, the truck has much less stopping power than with only the front circuit left.

• A (correct): Weight shifts forward when braking, so the front brakes carry well over half the load; losing them leaves only the weaker rears.
• B: A tandem master cylinder keeps the other circuit working, so partial braking remains with either leak.
• C: Which wheels are driven does not decide braking share; weight transfer makes the fronts do most of the stopping.
• D: Pressure may be similar, but the front brakes are larger and their tires carry more load while stopping, so they matter more.

Answer: C

Correct answer: 8.0 m/s². Reaction distance: 20 m/s x 1.5 s = 30 m at full speed, so only

m remain for braking.

Rearranging

• A: This uses the whole 55 m as braking distance, forgetting the 30 m covered during the reaction time.
• B: This subtracts the reaction distance but leaves out the 2 in a = v²/2d.
• C (correct): Reaction distance is 20 x 1.5 = 30 m, leaving 25 m to brake, so a = 20² ÷ (2 x 25) = 8.0 m/s².
• D: This divides 20² by 55, ignoring both the reaction distance and the 2 in the formula.

Answer: C

Correct answer: The inner surface of the drum. In a drum brake the shoes are mounted on a fixed backing plate inside a drum that turns with the wheel. The wheel cylinder pushes the shoes outward so their lining rubs the inner surface of the drum.

• A: Clamping both faces of a rotor is how disc brake pads work, not drum shoes.
• B: The shoes sit inside the drum and push outward; they do not wrap around the outside.
• C (correct): Drum brake shoes are pushed outward by the wheel cylinder against the inside of the turning drum.
• D: The backing plate is the fixed mount the shoes ride on; rubbing it would not slow the wheel.

Answer: D

Correct answer: The pad lining is worn away and metal is rubbing on the rotor. The earlier squeal was the wear indicator warning that the pads were thin. Grinding is more serious: the lining is gone and metal is rubbing on metal, which damages the rotor quickly and reduces braking, so service is needed right away.

• A: ABS pulsing happens only in hard stops near wheel lock and feels like buzzing, not grinding on every stop.
• B: The wear tab produces a squeal as an early warning; the grinding came after that warning was ignored.
• C: Fluid level does not cause a grinding noise at the wheel; worn-out lining does.
• D (correct): Grinding usually means the friction material is gone, so the backing metal is cutting into the rotor.

Answer: D

Correct answer: The fluid absorbs moisture, which lowers its boiling point and promotes rust. Glycol-based fluids such as DOT 3, 4 and 5.1 slowly absorb moisture through seals, hoses and the reservoir vent. Water lowers the boiling point, so hot brakes can form vapor and give a soft pedal, and it also promotes internal rust. Replacing the fluid at set intervals removes that moisture.

• A: Healthy fluid stays nearly incompressible as it ages; the problem is absorbed water, not the fluid thickening or turning gas-like.
• B: Brake fluid is not burned or consumed during braking; a falling level points to pad wear or a leak.
• C: DOT 5 is a separate silicone-based chemistry; glycol fluid never converts into it with age.
• D (correct): Glycol fluid is hygroscopic; the water it collects makes it easier to boil and corrodes internal parts.

Answer: A

Correct answer: The stop-lamp switch near the pedal arm. The brake lights are turned on by a switch near the brake pedal arm that closes the circuit when the pedal moves. If that switch fails or is out of adjustment, the lights can stay dark or stay on constantly.

• A (correct): This switch closes the brake-light circuit when the pedal moves; a failed or misadjusted one can leave the lights stuck on.
• B: The reservoir stores spare brake fluid and has no role in switching the brake lights on or off.
• C: Wheel-speed sensors feed the ABS controller; they do not control the brake lights.
• D: A torn booster diaphragm makes the pedal hard to push and may cause a hiss, but it does not keep the brake lights on.

Answer: B

Correct answer: It acts as a generator, recharging the battery while its drag slows the car. In regenerative braking the wheels drive the traction motor, which works as a generator and recharges the battery. The resistance of making electricity slows the car, and a controller blends this with the normal friction brakes.

• A: The motor is not part of the hydraulic system; regeneration slows the car electrically, not by adding fluid pressure.
• B (correct): The wheels turn the motor, which produces electricity, and that electrical load creates drag that slows the vehicle.
• C: Regeneration does not reverse the wheels; it resists their turning by producing electricity.
• D: Friction brakes are still needed for hard stops, low speeds, a full battery and faults, so the motor cannot replace them.

Answer: D

Correct answer: 225,000 J. Convert speed first: 54 km/

• A: This plugs 54 straight into the formula without converting km/h to m/s first.
• B: This converts the speed correctly but leaves out the one-half in the energy formula.
• C: This converts the speed but forgets to square it.
• D (correct): 54 ÷ 3.6 = 15 m/s, and KE = 0.5 x 2,000 x 15² = 225,000 J.

Answer: C

Correct answer: Seized rear self-adjusters, leaving a growing gap between shoes and drums. When drum lining wears, the gap between shoes and drum grows, so the wheel cylinder needs more fluid and more pedal travel to reach the drum. A self-adjuster normally takes up that gap; if it seizes, the pedal gets low and the parking brake, which uses the same rear shoes, needs more lever travel. A firm pedal and no leaks rule out air and fluid loss.

• A: Air would compress and make the pedal spongy, but this pedal is firm, and air would not affect the cable-worked parking brake.
• B: Lost booster assist makes the pedal hard to push; it does not make the pedal low or the parking lever travel farther.
• C (correct): As the lining wears and the adjuster no longer takes up the gap, the shoes travel farther, lowering the pedal and lengthening parking lever travel.
• D: Front pad wear may cause a squeal but would not change parking lever travel, and disc calipers adjust for wear on their own.

Answer: C

Correct answer: Pressure applied to a confined fluid is transmitted equally throughout the fluid. Pascal's principle says pressure applied to a confined fluid is passed equally to every part of that fluid. Because

a caliper piston with more area than the master piston receives more force at the same pressure.

• A: Pressure is equal, not force; a larger piston receives more force from the same pressure.
• B: The pressure is the same throughout the confined fluid, not highest at the input piston.
• C (correct): This is why every piston in one brake circuit sees the same pressure.
• D: Brake fluid is treated as nearly incompressible; that is what lets it transmit pressure.

Answer: B

Correct answer: 20 cm². Find the line pressure:

N ÷ 2.5 cm² = 100 N/cm². The same pressure acts on the caliper piston, so

eight times the master area for eight times the force.

• A: This is only the force ratio, 2,000 ÷ 250; it must still be multiplied by the 2.5 cm² master area.
• B (correct): Pressure is 250 ÷ 2.5 = 100 N/cm², so the needed area is 2,000 ÷ 100 = 20 cm².
• C: This divides 2,000 by 250 x 2.5, multiplying force by area instead of finding pressure as force divided by area.
• D: This squares the force ratio as if it were a diameter ratio; force scales directly with area.

Answer: A

Correct answer: To keep the rear wheels from locking before the fronts as weight shifts forward. When a car decelerates, load shifts toward the front axle, so the front tires grip better and the rear tires lose some grip. Limiting rear pressure keeps the lightly loaded rear wheels from locking first, which could make the car spin.

• A (correct): Braking unloads the rear tires, so they have less grip and would lock first if they got full pressure.
• B: Weight transfer moves load to the front, so the front tires gain grip and the rears lose some.
• C: Limiting rear pressure is about wheel lock and grip, not fluid boiling point.
• D: The parking brake is applied mechanically or by electric motors; it is not what the proportioning valve controls.

Answer: C

Correct answer: About 6.7 m/s. Rearrange

to

Ice cuts grip to one fifth, so speed must drop by a factor of

ABS keeps steering control but cannot change this limit.

• A: This cuts the speed by the full factor of 5, but distance depends on speed squared, so speed only drops by the square root of 5.
• B: ABS cannot raise tire grip, so the car cannot stop from the dry-road speed in the same distance on ice.
• C (correct): Solving $v^2=2ad=2\times 1.5\times 15=45$ gives v of about 6.7 m/s.
• D: This multiplies the speed by the square root of 5 instead of dividing, which would need a far longer distance.

Answer: B

Correct answer: DOT 5. DOT 3, DOT 4 and DOT 5.1 are all glycol-based fluids with different boiling points. DOT 5 is silicone-based and should not be mixed with them, so always use the type named on the reservoir cap or in the owner's manual.

• A: Despite the similar number, DOT 5.1 is glycol-based like DOT 3 and DOT 4.
• B (correct): DOT 5 is silicone-based, a different chemistry from the glycol-based DOT 3, 4 and 5.1.
• C: DOT 4 is a glycol-based fluid with a higher boiling point than DOT 3.
• D: DOT 3 is a common glycol-based fluid, not silicone.

Answer: D

Correct answer: A thinner rotor has less mass to absorb heat, so it overheats and fades sooner. Rotors and drums store the heat of each stop in their mass and then shed it to the air. Wear or machining removes metal and reduces that heat capacity, so a rotor below minimum thickness gets too hot faster and is more likely to fade or be damaged.

• A: Rotor thickness has nothing to do with fluid compressibility; air or vapor in the fluid causes a soft, spongy pedal.
• B: The red lamp responds to the parking brake, fluid level or hydraulic faults, not rotor thickness.
• C: Wheel-speed sensors read a toothed or magnetic ring, not the rotor faces, so rotor thickness does not affect them in any stop.
• D (correct): Rotors act as heat sinks; less metal means less heat capacity during a stop.