Examiners across all 50 states report a remarkably consistent list of most-missed pre-trip inspection items. Master these dozen and you'll dramatically improve your skills-test pass rate.
1. Slack adjuster pull
You must physically pull on the slack adjuster on each brake to verify free play of less than one inch. Many candidates "show" the inspection without actually pulling. Examiners watch specifically for the physical pull motion.
2. Belt deflection
Belt deflection should be no more than 3/4 inch with normal hand pressure. Candidates frequently say "checking belt tension" without actually pressing on the belt to demonstrate deflection.
3. Air-tank drains
You must identify the location of all air tanks (typically primary, secondary, wet) and explain that drains should be opened to expel water from the system. Many candidates miss the location of the wet tank entirely.
4. Steering linkage components
Pitman arm, drag link, tie rod, kingpin — each must be identified by name and inspected for missing nuts, broken welds, and excessive play. "I'm checking the steering" is not enough; examiners want each component named.
5. Brake chamber and push rod
Brake chambers (typically Type 30) must be checked for cracks, dents, or signs of leaking. The push rod travel should be checked when the brake is applied — typically 1 to 2 inches of travel for standard chambers.
6. Fifth wheel coupling
(Class A only) The fifth wheel must be properly greased; the jaws must be closed around the kingpin; the locking lever must be in the locked position; and the safety latch (where applicable) must be engaged. Many candidates miss the locking lever and safety latch as separate inspection items.
7. Tire tread depth
Steer-axle tires require 4/32" minimum tread; all other axles require 2/32" minimum. Demonstrate measurement with a tread gauge if your state allows; otherwise verbalize the depth requirements explicitly.
8. Tire condition (sidewall)
Sidewall cuts, bulges, or cord exposure are out-of-service violations. Demonstrate that you're inspecting the sidewall, not just the tread.
9. Lug nut torque indicators
Many trucks use rust trails or torque-indicator markers (yellow paint stripes) to show lug-nut tightness. A broken paint line indicates a loose nut. Identify these and verify all lug nuts are properly torqued.
10. Mud flaps and reflectors
Mud flaps must be present and intact; rear reflectors and conspicuity tape must be present and clean. Examiners include these in the walk-around inspection and routinely fail candidates who skip them.
11. Air-line gladhands and electrical connection
(Combination vehicles) The blue (service) and red (emergency) gladhands must be properly connected, supported off the catwalk, and free of cracks or leaks. The electrical pigtail must be connected and supported.
12. Suspension components
Leaf springs, U-bolts, shock absorbers, air bags (on air-suspension vehicles), and torque rods must each be identified and inspected. Many candidates skip the U-bolts and torque rods entirely.
Drill these in your pre-trip checklist practice and on every state-specific practice test.