CDL Air Brake Brake Adjustment and Maintenance 3

Question 1

What are the signs of worn or damaged brake shoes a driver should look for during inspection?

Accepted Answer

Shiny metal surfaces, no visible lining material, or lining contaminated with oil

Answer

Any discoloration of the outer brake drum surface

Answer

Brake chambers that appear physically larger than normal

Answer

Air supply lines that feel warm to the touch during inspection

Question 2

What is the recommended frequency for professional brake inspections on commercial vehicles under federal regulations?

Accepted Answer

Per manufacturer specs and federal requirements, typically every 12,500 miles or 6 months

Answer

Annually only, regardless of mileage

Answer

Only when the driver notices reduced braking performance

Answer

Every 100,000 miles as a standard interval

Question 3

What is the purpose of brake shoe return springs in a drum brake assembly?

Accepted Answer

To retract brake shoes away from the drum when brakes are released

Answer

To increase braking force when brakes are applied

Answer

To hold slack adjusters in the adjusted position

Answer

To maintain air pressure inside the brake chambers

Question 4

What can happen if brake chambers are not properly sealed and moisture enters the chamber?

Accepted Answer

Moisture causes corrosion of internal components including the diaphragm and push rod, leading to failure

Answer

Air pressure will automatically expel moisture during normal braking

Answer

The push rod will automatically compensate for any corrosion

Answer

The governor will detect moisture and compensate with higher pressure

Question 5

How does very cold weather affect air brake system performance?

Accepted Answer

Moisture in lines can freeze and rubber components can stiffen, potentially affecting brake function

Answer

Cold weather always improves braking performance due to denser air

Answer

Cold weather has no measurable effect on air brake system performance

Answer

Brakes become more effective because denser cold air increases system pressure

Question 6

Why is it important to keep S-cam shafts and slack adjusters properly lubricated?

Accepted Answer

Proper lubrication prevents corrosion, reduces wear, and ensures smooth and consistent brake application

Answer

Lubrication is not required for any air brake mechanical components

Answer

Only the compressor requires lubrication — other components are self-lubricating

Answer

Lubricating mechanical brake components actually increases stopping distance