Florida CDL — Air Brakes: Safe Driving Practices Practice Test

Question 1

Why must air storage tanks be drained regularly if they only have manual drain valves?

Accepted Answer

To remove the water and compressor oil that collect inside them — Compressed air carries water and compressor oil into the tanks. That sludge can freeze in cold weather and cause brake failure, so tanks with manual drains should be drained at the end of each day of driving.

Answer

To keep the tanks from over-pressurizing the governor

Answer

To recharge the spring brake chambers

Answer

To test the low air pressure warning device

Question 2

While inspecting a manual slack adjuster on an s-cam brake, you pull hard on it with the wheels chocked and parking brakes released. When does it need adjustment?

Accepted Answer

If it travels more than about one inch at the point where the push rod connects — A manual slack adjuster that travels more than about an inch at the push rod connection probably needs adjusting. Brakes out of adjustment are the problem roadside inspectors find most often, and too much slack makes a vehicle hard to stop.

Answer

If it moves at all

Answer

Only if it cannot be moved by hand

Answer

If it moves less than about one inch

Question 3

During a static leakage test on a straight truck — engine off, service brakes released — what is the most air pressure loss allowed in one minute?

Accepted Answer

2 psi — With a fully charged system, engine off and brakes released, a single vehicle may lose no more than 2 psi in one minute. A combination vehicle is allowed up to 3 psi per minute.

Answer

4 psi

Answer

6 psi

Answer

No loss at all is permitted

Question 4

Heading down a grade, you see the application pressure gauge creeping higher because you must press harder just to hold the same speed. What does this tell you, and what should you do?

Accepted Answer

The brakes are fading; slow down and shift to a lower gear — Needing more application pressure to keep a steady speed is a warning sign of brake fade, so reduce your speed and select a lower gear. Air leaks, mechanical faults, or poorly adjusted brakes can produce the same symptom.

Answer

The governor has cut in; keep the same gear and pedal pressure

Answer

The tanks are overfilled; open the drain valves at the bottom

Answer

The ABS is engaging; release the pedal fully and coast

Question 5

In the s-cam drum brake found on most heavy vehicles, pressing the brake pedal ultimately causes the s-shaped camshaft to:

Accepted Answer

Turn and force the brake shoes apart against the inside of the drum — Air pressure moves the push rod and slack adjuster, twisting the brake camshaft. The turning s-cam forces the brake shoes apart and presses them against the inside of the brake drum to create stopping friction.

Answer

Pull the brake shoes away from the drum

Answer

Compress the return springs so the wheel spins freely

Answer

Squeeze a caliper against a rotor

Question 6

The governor on an air brake system will usually stop the compressor from pumping once tank pressure climbs to about:

Accepted Answer

125 psi — The governor's cut-out point is around 125 psi. When the tanks reach that level, the governor stops the compressor from pumping more air.

Answer

60 psi

Answer

100 psi

Answer

150 psi

Question 7

Before pulling out in a truck with a dual air brake system, how much pressure should you let the compressor build in the primary and secondary systems?

Accepted Answer

At least 100 psi in both systems — With a dual air system, give the compressor time to bring the primary and the secondary system each up to at least 100 psi before you drive, keeping an eye on both gauges (or both needles on a two-needle gauge).

Answer

At least 55 psi in the primary system only

Answer

At least 85 psi in whichever system reads lower

Answer

At least 125 psi in the secondary system only

Question 8

Your truck has automatic slack adjusters, and on your walk-around you find a brake whose pushrod stroke is past the legal adjustment limit. What does the handbook recommend?

Accepted Answer

Take it to a repair shop promptly so the real fault gets fixed — On an automatic adjuster, a stroke beyond the limit points to a mechanical fault in the adjuster, the foundation brake parts, or the installation. Adjusting it by hand usually hides that fault instead of curing it, so get it repaired promptly; a manual adjustment is only a stopgap for an emergency.

Answer

Adjust it by hand and keep running the truck as usual

Answer

Make a few hard stops so the adjuster resets itself, then drive on

Answer

Back off the other slack adjusters so every brake matches

Question 9

Your older tractor has a front brake limiting valve with 'normal' and 'slippery' settings. According to the handbook, how should you use it?

Accepted Answer

Keep it in the normal position, because front-wheel braking skids are unlikely even on ice — Tests have shown that front wheel skids from braking are not likely even on ice, so limiting front brake pressure just reduces stopping power. Leave the valve in the normal position.

Answer

Switch it to slippery whenever it rains to prevent jackknifing

Answer

Alternate between settings every few miles to keep the valve from sticking

Answer

Use slippery mode in town and normal mode on the highway

Question 10

You hold the brake pedal fully applied on a tractor-trailer with the engine off during the applied leakage test. The air loss rate that means the system fails the check is more than:

Accepted Answer

4 psi per minute — With the brakes held applied, air loss must not exceed 3 psi per minute for a single vehicle or 4 psi per minute for a combination vehicle. A faster leak must be fixed before driving.

Answer

1 psi per minute

Answer

2 psi per minute

Answer

8 psi per minute

Question 11

An air brake setup is really three braking systems in one. Which of them borrows components from the other two to bring the vehicle to a halt when the brakes fail?

Accepted Answer

The emergency brake system — The handbook splits air brakes into service, parking, and emergency systems. The emergency system relies on pieces of the service and parking systems to halt the vehicle if the brake system breaks down.

Answer

The service brake system

Answer

The parking brake system

Answer

The antilock braking system

Question 12

What information does the supply pressure gauge on the dash give you?

Accepted Answer

How much air pressure is in the air tanks — The supply pressure gauge shows how much air pressure is stored in the air tanks. Vehicles with dual air systems either have two gauges or one gauge with two needles.

Answer

How much pressure you are sending to the brake chambers right now

Answer

How worn the brake linings are

Answer

The temperature of the brake drums

Florida CDL — Air Brakes: Safe Driving Practices practice test

Study questions with answers

1. Why must air storage tanks be drained regularly if they only have manual drain valves?

2. While inspecting a manual slack adjuster on an s-cam brake, you pull hard on it with the wheels chocked and parking brakes released. When does it need adjustment?

3. During a static leakage test on a straight truck — engine off, service brakes released — what is the most air pressure loss allowed in one minute?

4. Heading down a grade, you see the application pressure gauge creeping higher because you must press harder just to hold the same speed. What does this tell you, and what should you do?

5. In the s-cam drum brake found on most heavy vehicles, pressing the brake pedal ultimately causes the s-shaped camshaft to:

6. The governor on an air brake system will usually stop the compressor from pumping once tank pressure climbs to about:

7. Before pulling out in a truck with a dual air brake system, how much pressure should you let the compressor build in the primary and secondary systems?

8. Your truck has automatic slack adjusters, and on your walk-around you find a brake whose pushrod stroke is past the legal adjustment limit. What does the handbook recommend?

9. Your older tractor has a front brake limiting valve with 'normal' and 'slippery' settings. According to the handbook, how should you use it?

10. You hold the brake pedal fully applied on a tractor-trailer with the engine off during the applied leakage test. The air loss rate that means the system fails the check is more than:

11. An air brake setup is really three braking systems in one. Which of them borrows components from the other two to bring the vehicle to a halt when the brakes fail?

12. What information does the supply pressure gauge on the dash give you?

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