CDL air brakes practice test 5

C: Powerful springs are held back by air pressure; if the air is removed, the springs put on the brakes. While you drive, air pressure holds back powerful springs. Remove the air, with the parking control or through a leak, and the springs apply the brakes. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.14 Spring Brakes, page 5-3.

B: The brakes being in adjustment. Spring brakes act through the same foundation brakes, so if the brakes are poorly adjusted, both the service brakes and the parking/emergency brakes lose effectiveness. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.14 Spring Brakes, page 5-3.

B: March 1, 1997. ABS is required on air-braked truck tractors built on or after March 1, 1997 (also 49 CFR 393.55(c)(1)). Other air-braked vehicles followed a year later. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

B: March 1, 1998. For air-braked vehicles other than truck tractors (trucks, buses, trailers and converter dollies), ABS is required if built on or after March 1, 1998 (49 CFR 393.55(c)(2)). Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

C: Check the certification label for the date of manufacture. Check the certification label for the date of manufacture to find out whether the vehicle is equipped with ABS. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

C: Keeps your wheels from locking up during hard braking. ABS is a computerized system that keeps the wheels from locking up during hard brake applications. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

A: Yellow. ABS malfunction lamps are yellow. The red light is the low air pressure warning. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

A: On the left side, on either the front or rear corner. Trailers have yellow ABS malfunction lamps on the left side, on either the front or the rear corner. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

B: Until you are driving over 5 mph. On newer vehicles the lamp comes on for a bulb check and goes out quickly. On older systems it may stay on until you are driving over five mph. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

D: You may have lost ABS control at one or more wheels. If the lamp stays on after the bulb check or comes on while driving, you may have lost ABS control at one or more wheels. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

A: Look under the vehicle for the electronic control unit (ECU) and wheel speed sensor wires coming from the back of the brakes. Look under the vehicle for the ECU and for wheel speed sensor wires coming from the back of the brakes. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

C: It neither increases nor decreases it; it is an addition to your normal brakes. ABS is an addition to your normal brakes. It doesn't decrease or increase your normal braking capability, and it only activates when wheels are about to lock. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

A: ABS does not necessarily shorten stopping distance, but it helps you keep control during hard braking. ABS keeps the wheels from locking, which helps you stay in control in a hard stop, but it won't always make the stopping distance shorter. Commercial Driver's License Manual (CDL Driver's Manual): 5.1.16 Antilock Braking Systems (ABS), page 5-4.

C: Two separate air brake systems that use a single set of brake controls. A dual air brake system has two separate air brake systems, each with its own tanks, hoses, and lines, but they share one set of brake controls. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

A: The regular brakes on the rear axle or axles. In the typical layout, the primary system handles the rear axle(s) and the secondary system handles the front axle, sometimes with one rear axle too. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

C: The regular brakes on the front axle, and possibly one rear axle. In the typical layout, the secondary system brakes the front axle and sometimes one rear axle. The primary handles the rear axle(s), and both feed air to any trailer. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

C: 100 psi. Allow time for the compressor to build a minimum of 100 psi in both the primary and secondary systems before driving. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

C: 55 psi. The manufacturer's shut-off value must be greater than 55 psi. Commercial Driver's License Manual (CDL Driver's Manual): 5.2 Dual Air Brake, page 5-5.

A: The basic seven-step inspection, with extra air brake checks. Use the seven-step inspection from Section 2. Vehicles with air brakes have more things to check, and these fit into the seven steps. Commercial Driver's License Manual (CDL Driver's Manual): 5.3 Inspecting Air Brake Systems, page 5-6.

D: The condition and tightness of the drive belt. If the compressor is belt-driven, check that the belt is tight and in good condition during the engine compartment step. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.1 During Step 2 Engine Compartment Checks, page 5-6.

B: Park on level ground, chock the wheels, and release the parking brakes. Park on level ground and chock the wheels so the vehicle can't move. Then release the parking brakes so you can move the slack adjusters. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

C: About one inch. Pull hard on the slack adjuster with gloves on. Free play of more than roughly one inch at the push rod connection usually means it needs adjusting. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

C: Out-of-adjustment brakes. Brakes out of adjustment are the problem inspectors find most often at roadside inspections, which is why checking slack adjusters matters. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

B: 1994. The manual says all vehicles built since 1994 have automatic slack adjusters. 49 CFR 393.53(b) requires them on air-braked CMVs built on or after October 20, 1994. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.

C: Yes; even though they adjust during full brake applications, they must be checked. Even though automatic slack adjusters adjust themselves during full brake applications, they still must be checked. Commercial Driver's License Manual (CDL Driver's Manual): 5.3.2 During Step 5 Walk-around Inspection, page 5-6.