CDL Pre-Trip Inspection

What the pre-trip inspection test covers, the parts you check before every trip, and the numbers for the air brake check.

Air Brakes Practice Test · General Knowledge Test

What You Check

A fifth wheel coupling seen from above, with its slot and locking jaws
The coupling On a tractor-trailer, the fifth wheel’s jaws locked around the kingpin. Photohelp13, CC BY-SA 4.0
The backs of two tractors, with their coiled air and electrical lines
Air lines Air and electrical lines secure, with no leaks, tangles or rubbing. MobiusDaXter, CC BY-SA 3.0
A truck hauling a wide load, seen in a side mirror on a curving highway
Mirrors Mirrors clean, secure and set to see along both sides. born1945, CC BY 2.0

Some photos cropped or edited.

What’s on the pre-trip inspection test?

You point out each safety part and say what you’re checking it for. The test covers the engine compartment, the cab and engine start, steering, suspension, brakes, wheels, the sides and rear of the vehicle, and the special parts of a tractor-trailer, school bus or coach if you test in one.

Test in a vehicle with air brakes and you add the air brake check.

49 CFR 383.113(a).

What must I check before every trip?

That these work: service brakes and the trailer’s brake connections, parking brake, steering, lights and reflectors, tires, horn, wipers, mirrors, coupling devices, wheels and rims, and emergency equipment.

If the last inspection report lists defects, read it and sign that the repairs were made. At the end of the day, report any defect you found.

49 CFR 392.7(a), 396.11 and 396.13.

How much tire tread do I need?

At least 4/32 inch on the front tires of a truck, tractor or bus, and 2/32 inch on the rest. No tire may be flat, leaking, or cut or worn through to the ply or belt.

49 CFR 393.75.

What are the numbers for the air brake check?

The figures most state CDL manuals use. Where the vehicle maker’s differ, follow the maker’s.

CheckWhat you should see
GovernorThe compressor stops near 125 psi and starts again near 100 psi
Air buildupRises from 85 to 100 psi in 45 seconds or less (dual system)
Leaks, brakes releasedUnder 2 psi a minute (3 on a combination)
Leaks, foot brake heldNo more than 3 psi in a minute (4 on a combination)
Low air warningOn before pressure falls below 55 psi
Spring brakesCome on between 20 and 45 psi
Parking brakeHolds when you pull gently against it in a low gear
Service brakeStops you straight from about 5 mph

49 CFR 383.113(a)(2); the state CDL manuals’ air brake section.

More Guides

How to Get a CDL · CDL Rules · CDL Classes and Endorsements · ELDT