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Repair 1 > Brake Repair > Flashcards

Brake Repair Flashcards

1
Q

What things effect kinetic energy?

A

Kinetic energy is a mix of mass and speed squared.

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2
Q

What things effect friction?

A

Pressure between two surfaces, composition of materials, and condition of surfaces.

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3
Q

What is the equation of the coefficient of friction?

A

Force to move an object / weight of object.

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4
Q

How does brake fade occur?

A

The brake rotor or drum absorbs heat faster than it dissipates it, the drum or rotor will reach a point where it can’t absorb anymore heat.

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5
Q

What is mechanical fade?

A

When the brake drums expand so much that the shoes no longer reach the drum.

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6
Q

What is lining fade?

A

When friction material overheats, its COF drops due to “thermal saturation”.

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7
Q

What is hydraulic fade?

A

When brake fluid reaches boiling point, fluid starts to vaporise and bubble, the vapour compresses rather than transferring pressure.

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8
Q

What is Pascal’s law?

A

It states that fluid pressure is applied in a uniform manner.

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9
Q

How does Pascal’s law effect brake pistons?

A

If the master cylinder has a 10cm2 piston, and the front brakes have a 20cm2 piston. 10N on the master cylinder piston would equal 20N on the brake piston.

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10
Q

What characteristics does brake fluid need?

A

Remain viscous at high/low temps, have a high boiling point, and act as a lubricant.

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11
Q

What is the most common brake fluid chemical used?

A

Polyglycol.

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12
Q

What are the advantages/disadvantages of silicone brake fluid, and what DOT type is it found in?

A

It is good because it is not hygroscopic, it has a high boiling point, and doesn’t ruin paint. Although it is hard to bleed air from it. It is found in DOT 5 fluid.

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13
Q

What metals are in brake tubing?

A

Copper-plated steel sheets, then plated with tin and zinc for corrosion protection.

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14
Q

What are the main components in a brake drum assembly?

A

Backing plate, brake shoes, return/anchor/hold-down springs, wheel cylinder, and adjuster.

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15
Q

What happens when a leading edge shoe is pressed against the brake drum?

A

Friction is increased through a reactive force known as self-energising or servo action.

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16
Q

How does a duo-servo drum setup work?

A

Both shoes are anchored at the top, the primary shoe gets wedged into the drum, then the motion is transferred to the secondary shoe through the shoe-adjusting screw assembly.

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17
Q

How does a leading-trailing drum setup work?

A

When the leading shoe is pressed against the drum, the drum pushes the shoe into the anchor which wedges the top of the shoe harder into the drum.

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18
Q

What does the compression spring do in a wheel cylinder?

A

When the master cylinder draws fluid back from the wheel cylinder, the inertia could cause a vacuum and allow air to enter through the system past the piston cup, the compression spring holds the piston cups in contact with the cylinder wall.

19
Q

What is a brake drum normally made of?

A

Cast iron with a mild steel centre.

20
Q

How high can friction heat reach in a brake drum?

A

Up to 315 degrees.

21
Q

What characteristics does a brake drum need?

A

Accurately balanced, sufficiently rigid, resistant to wear, highly heat conductive, lightweight, correct COF.

22
Q

How does the brake pad move back after the brake pedal has been pressed?

A

The seal of the caliper piston flexes when the piston pushes out, when the pedal is released the seal flexes back to the original position which brings the pad back.

23
Q

What are the main components of the brake booster?

A

The body, booster piston and diaphragm, piston return spring, and control valve assembly.

24
Q

What are the two vacuum booster designs?

A

Single diaphragm and tandem diaphragm.

25
Q

What is the importance of a reservoir cap on a master cylinder?

A

It is vented to atmosphere so that if fluid drops it doesn’t create a vacuum.

26
Q

How does a proportioning valve work?

A

Up to the “split point”, fluid passes the p.valve’s cylinder cup, as pressure from the rear brakes increases, it pushes the p.valve’s piston to the left, closing off the gap in the cylinder cup and stopping flow to the brakes.

27
Q

How does the vacuum booster work?

A

There are two pressure chambers, one with vacuum and one that can have vacuum or atmospheric pressure, when the brake are pressed, the valve which allows atmospheric pressure to enter the variable chamber opens and the atmospheric pressure pushes against a diaphragm between the two chambers, assisting in brake force.

28
Q

How does a master cylinder work?

A

There are two pistons in the cylinder, when the brakes are pressed, the first piston is activated, when it pushes out far enough, it pushes against the second piston which opens up the second brake circuit.

29
Q

What are the main types of proportioning valves?

A

Single p.valve, p and bypass valve, dual p.valve, load sensing p.valve, load sensing and bypass valve.

30
Q

What does the bypass circuit do in a proportioning valve?

A

If the front wheel circuit fails, it stops the function on the proportioning valve, allowing full pressure to the rear wheels.

31
Q

What does a dual p.valve do?

A

They are in FF cars, as there are two circuits which run to the rear wheels, as FF cars have front and rear brakes activated on each circuit, there is no need for a bypass function.

32
Q

What does a LSPV do?

A

It senses how much weight is over the rear tyres and adjusts what the “split point” would be, varying at what point the proportioning valve starts to operate.

33
Q

What is slip ratio, and what is the ideal level of slip?

A

Slip ratio is the difference between vehicle speed and the speed of the wheels. Ideal ratio is between 10-30%

34
Q

What components does the ABS system include?

A

Skid control ECU, brake actuator, wheel speed sensor, combination meter, stop light switch, and deceleration sensor.

35
Q

What does a typical ABS brake actuator generally consist of?

A

Pressure holding solenoid valve, pressure reduction solenoid valve, pump motor, and resevoir.

36
Q

What is the initial check function on an ABS module?

A

Each time the vehicle is turned on and travelling faster than 6km/h, the skid control ECU operates the solenoid valves in sequence in order to check the electrical system of the ABS.

37
Q

What is the diagnostic function on an ABS module?

A

If a fault is found in the ABS system, the ABS light will come on the combination meter and a DTC will be stored.

38
Q

What is the fail-safe function on an ABS module?

A

If the skid control ECU detects a fault in the system electrical current from the ECU to the actuator is turned off, making the car act as if there is no ABS, but still functioning.

39
Q

How does EBD work when travelling in a straight line?

A

The skid control ECU senses wheel speeds between front and rear wheels, which can vary depending on loads, and will distribute brake force accordingly.

40
Q

How does EBD work when cornering?

A

When cornering, the inside wheels have less load than the outside wheels, the skid control ECU receives signals from speed sensors and applies more brake force to the to the wheels with more traction.

41
Q

What does brake assist do?

A

In emergency braking situations, a driver may not press hard enough on the pedal for the full braking force to be achieved. The BA system uses a pressure sensor in the ABS actuator to detect the speed and force of the pedal being depressed.

42
Q

What does TRC do?

A

If too much throttle is applied during take off or while driving on slippery surfaces and the wheels start to slip, the ABS actuator will apply brake force to the drive wheels and the motor output will be reduced.

43
Q

What does VSC do?

A

The vehicle stability control system is used to help stabilise the car through cornering, the system detects steering slip and applies brake force according to each wheel to help stabilise the vehicle.

44
Q

How does a hydraulic brake booster work?

A

The booster uses a pump, pump motor, pressure relief valve, accumulator pressure sensor, and accumulator to build pressure inside the accumulator and uses that pressurised fluid to assist in brake force.

Repair 1 (6 decks)

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