A commercial truck maintenance checklist built on pass-fail limits
Most checklists say "check the brakes." Federal rules say exactly when a brake, tire, or steering part fails. Check against those limits, and the truck fails in your yard instead of at the roadside.
Written by Gabriel Gonzalez
The checklist in numbers
A commercial truck maintenance checklist should follow the minimum periodic inspection standards in Appendix A to 49 CFR Part 396: brakes, coupling devices, exhaust, fuel, lights, steering, suspension, frame, tires, wheels, windshield, wipers, and rear impact guard, each checked against the measurable limit where it fails.
Every truck placed out of service is a load that doesn't deliver and a customer who waits. Most of those stops come from items a shop could have measured the week before: brake stroke, tread depth, a leaking hose.
I have spent more than 22 years at Simplex, nearly 16 of them as COO, and I now lead revenue strategy. This checklist is organized the way inspectors look at a truck, system by system, with the number that decides pass or fail, so your maintenance dollars go to what keeps the truck earning.
The full briefing, read aloud
8 chapters. Select one to jump to it.
Generated with AI text-to-speech from this article's key insights, in order, rather than reading it word for word. Chapter times come from a transcript of the audio. The article itself was written and reviewed by Gabriel Gonzalez.
Key takeaways
One federal standard sets the limits
Appendix A to Part 396 lists what fails a periodic inspection, and carriers must keep parts at, or promptly repaired to, that standard all year.
Brakes and tires lead roadside stops
At CVSA's 2026 International Roadcheck, brake problems made up 39.1% of vehicle out-of-service violations and tires 20.9%.
Measure, don't eyeball
Pushrod stroke, lining thickness, tread depth, steering lash, and air suspension leakage all have numeric limits.
Every unit gets its own inspection
Tractor, trailer, and converter dolly each need a periodic inspection at least once every 12 months, with proof on the vehicle.
Engine service intervals are yours to set
Oil, filters, and coolant follow the manufacturer's schedule. Federal rules require lubrication and no leaks, but set no interval.
In this articleContents
What should a commercial truck maintenance checklist cover?
A commercial truck maintenance checklist should cover every system in Appendix A to 49 CFR Part 396, the federal minimum periodic inspection standards. A vehicle with any defect on that list does not pass.
Appendix A is more than the annual inspection form. Under 49 CFR 396.17(g), carriers must keep parts maintained at, or promptly repaired to, those standards. That makes it the pass-fail list for every service visit, not just the yearly one. It covers:
- Brakes: service and parking brakes, drums and rotors, hoses and tubing, warning devices, ABS, and the air compressor
- Tires, wheels, and rims
- Steering, suspension, and frame
- Coupling devices: fifth wheels, pintle hooks, drawbars, and safety devices
- Lights, exhaust, and the fuel system
- Windshield, wipers, the rear impact guard, and safe loading
The sections below take them in the order most likely to put a truck out of service.
What the federal list leaves out
Engine oil, filters, coolant, and aftertreatment service don't appear in Appendix A. Federal rules require only that each vehicle be properly lubricated and free of oil and grease leaks (49 CFR 396.5), and they set no service interval.
Those intervals come from your manufacturer's schedule and your duty cycle. Our guide to truck preventive maintenance covers how to set them and keep the records.
What fails on brakes and the air system?
Brakes fail on stroke, lining, leaks, and warning devices, and they stop more trucks than anything else. At CVSA's 2026 International Roadcheck, brake problems made up 39.1% of vehicle out-of-service violations.
| Check | Fails when | Rule |
|---|---|---|
| Pushrod stroke | Over the readjustment limit for the chamber, such as 2 in. on a standard Type 30 clamp chamber or 2 1/2 in. on a long-stroke one. Measure with the engine off, 80 to 90 psi, brakes fully applied | 393.47(e); App. A 1.a(5) |
| Linings and pads, non-steering axles | Under 1/4 in. at the shoe center on air drum brakes, under 1/8 in. on air disc brakes, or soaked with oil or grease | 393.47(d); App. A 1.a(6) |
| Drums and rotors | An external crack that opens when the brake is applied, a piece missing, or thinner than the manufacturer's limit | 393.47(g); App. A 1.c |
| Hoses and tubing | Damage through the outer reinforcement ply, bulging under pressure, an audible leak, or an improper splice | 393.45; App. A 1.d and 1.e |
| Low-pressure warning | Missing, or doesn't warn at 55 psi or half the governor cut-out pressure, whichever is less | 393.51(c); App. A 1.f |
| ABS malfunction lamps | Doesn't light at power-up, or stays lit | App. A 1.l |
| Air compressor | A drive belt close to failure, loose mounting bolts, or a cracked pulley | App. A 1.h |
Automatic slack adjusters get a rule of their own. Under Appendix A, a brake found out of adjustment must be checked for the reason, and manually adjusting an automatic adjuster without fixing the cause is not acceptable.
That is a cost question as much as a safety one: re-adjusting can hide a worn bushing or a cracked drum until it fails on the road. For what inspectors focus on during enforcement week, see our Brake Safety Week guide.
What fails on tires and wheels?
A steer tire fails under 4/32 inch of tread and any other tire under 2/32 inch, along with any tire that is flat, leaking, cut to the ply, or separating. Tires were 20.9% of vehicle out-of-service violations at Roadcheck 2026, second only to brake systems.
| Check | Fails when | Rule |
|---|---|---|
| Steer tire tread | Under 4/32 in. at any point on a major tread groove | 393.75(b) |
| All other tires | Under 2/32 in. in a major tread groove | 393.75(c) |
| Tire condition | Ply or belt exposed, tread or sidewall separation, flat or audibly leaking, or cut to the ply | 393.75(a) |
| Inflation and load | Cold pressure below what the load requires, or a load above the sidewall rating | 393.75(g) and (i) |
| Steer axle only | A boot or blowout patch, bias and radial tires mixed on the axle, or a regrooved tire rated 4,920 lb or more | 393.75(e); App. A 10.a |
| Wheels and rims | A crack, elongated bolt holes, loose or missing nuts, a bent or cracked lock ring, or a welded repair on a steer-axle aluminum wheel | 393.205; App. A 11 |
Check pressure cold. The rule judges cold inflation pressure against the load being carried, and a tire overloaded because of low pressure fails Appendix A too.
Tread depth is the number most worth trending. Logging it at every service shows which positions wear fastest, so tires get replaced on your schedule rather than at a roadside stop.
What fails on steering, suspension, frame, and coupling?
These systems fail on play, cracks, and anything loose or missing. Most of the limits can be checked with a tape measure and the dash air gauge.
| Check | Fails when | Rule |
|---|---|---|
| Steering wheel lash | Over the limit for the wheel size. On a 20-inch wheel: 2 1/2 in. with manual steering, 5 1/4 in. with power steering, engine running | 393.209(b); App. A 7.a |
| Steering linkage | A loose pitman arm, loose or missing nuts on tie rods or the drag link, more than 1/4 in. of play at a ball joint, or a welded repair | 393.209(d); App. A 7 |
| Suspension | A cracked, broken, loose, or missing U-bolt or axle positioning part, a broken leaf, or an air suspension losing more than 3 psi in 5 minutes | 393.207; App. A 8 |
| Frame | A cracked, broken, loose, or sagging member, loose or missing fasteners, or the body or frame touching a tire | 393.201; App. A 9 |
| Sliding subframe | Locking pins missing or not engaged | 393.207(b); App. A 9.c |
| Fifth wheel | More than 1/2 in. of horizontal movement between the upper and lower halves, a cracked plate, or locking parts missing or deformed | App. A 2.a |
| Pintle hooks and chains | Any crack or welded repair in the hook, or safety chains worn to a measurable loss in link cross section | App. A 2.b and 2.e |
Power steering adds its own items: belts that aren't frayed, cracked, or slipping, no leaks, and enough fluid in the reservoir (393.209(e)).
What fails on lights, exhaust, fuel, and the cab?
Every required lamp must work and stay visible, and that simple rule still accounted for 11.9% of vehicle out-of-service violations at Roadcheck 2026. The rest of this group is mostly about leaks and visibility.
- Lights and reflectors. Every required lamp works, and none is hidden by the load, dirt, or added equipment (393.9).
- Exhaust. No leak forward of or directly below the driver or sleeper compartment, no wrap or patch repairs, securely fastened, and nothing placed where it can burn wiring or the fuel supply (393.83).
- Fuel system. No visible leak, the filler cap in place, and the tank held with no loose, broken, or missing bolts or brackets (Appendix A, item 4).
- Windshield. Above the top of the steering wheel, outside a 2-inch top border and 1-inch side borders, damage is allowed only as a crack no other crack crosses, or a spot a 3/4-inch disc covers at least 3 inches from other damage (393.60).
- Wipers, horn, and mirrors. Working wipers and washers, a horn that gives a reliable warning, and an outside mirror on each side (393.78, 393.80, 393.81).
- Emergency equipment. A fire extinguisher rated 5 B:C or more, or two rated 4 B:C, plus three reflective triangles or at least six fusees (393.95). Our DOT fire extinguisher guide covers the details.
- Rear impact guard. On trailers rated 10,001 pounds or more and built on or after January 26, 1998, the guard must be secure, no more than 22 inches above the ground, and within 4 inches of each side (Appendix A, item 15).
Appendix A also fails a vehicle when the spare tire, load, or dunnage could fall onto the road, or when a required front-end structure is missing.
How do you run the checklist to avoid out-of-service stops?
Split it between the driver and the shop, measure the numbers, and fix before dispatch. Of 44,047 vehicle inspections at Roadcheck 2026, 23.5% ended with the vehicle placed out of service.
Each of those stops costs more than the repair. A vehicle declared out of service can't be driven until the repairs are done, and it can only be towed away by a vehicle using a crane or hoist (49 CFR 396.9). Wear and mechanical breakdown are maintenance costs, not insurance claims, as our physical damage insurance page explains.
Repairs are also getting more expensive. ATRI's 2026 Analysis of the Operational Costs of Trucking found repair and maintenance costs up 8.6% in 2025, while average truck age and annual mileage increased.
Step 1: Give the driver the daily part
Before driving, the driver must be satisfied that 11 items work, from service brakes to emergency equipment (49 CFR 392.7). At the end of each day, the driver reports any defect in writing (396.11). A carrier operating only one commercial motor vehicle is exempt from the written report, not from the check.
Step 2: Give the shop the measured part
Stroke, lining thickness, tread depth, steering lash, and air leakage need tools and a trained technician. Record the measurement, not just a check mark, so you see wear before a part reaches its limit.
Step 3: Fix before dispatch
Repair any reported defect likely to affect safety before the truck runs again, and certify the repair on the report (396.11). A vehicle may not be operated in a condition likely to cause an accident or a breakdown (396.7).
Step 4: Inspect every unit at least once a year
Tractor, trailer, and converter dolly each need a periodic inspection covering Appendix A at least once every 12 months, with proof on the vehicle (396.17). SimplexHub tracks the date each vehicle's next one is due.
Step 5: Feed roadside findings back into the checklist
Certify roadside violations as corrected within 15 days and keep the report for 12 months (396.9). When the same finding repeats, tighten the check or the interval. Repeat violations also build your Vehicle Maintenance BASIC, which can follow you into renewal; see how CSA scores affect truck insurance premiums.
How Simplex helps you keep trucks in service
A checklist is only as good as the records and follow-up behind it. We help with both.
Maintenance records and mock audits
Our compliance programs include maintenance records and a DOT mock audit, with monthly safety reviews in the Managed Program.
Repairs tracked in your ELD
Our ELD service includes electronic DVIRs, and the Premium plan adds repair and maintenance tracking with a mechanic app and portal.
A maintenance program that holds up
Our DOT safety compliance team sets up and maintains the documented vehicle maintenance program an FMCSA auditor samples.
Frequently asked questions
What should be on a commercial truck maintenance checklist?+
How often does a commercial truck need to be inspected?+
Is there a required commercial vehicle maintenance schedule?+
What is the minimum tread depth on a semi truck?+
Is there an official truck maintenance checklist form?+
Where this information comes from
The limits below come from federal regulations and from CVSA and ATRI data, checked on October 16, 2026.
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1
eCFR — Appendix A to 49 CFR Part 396
The minimum periodic inspection standards: what fails for each system.
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2
eCFR — 49 CFR 396.17
Annual inspection of each vehicle, and the duty to maintain parts to Appendix A.
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3
eCFR — 49 CFR Part 396
Lubrication, unsafe operation, out-of-service orders, DVIRs, and inspection reports.
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4
eCFR — 49 CFR Part 393
Equipment standards for brakes, lights, exhaust, fuel, glazing, steering, suspension, and frames.
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5
eCFR — 49 CFR 393.47
Brake readjustment limits and lining thickness.
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6
eCFR — 49 CFR 393.75
Tire tread depth, condition, load, and inflation rules.
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7
CVSA — 2026 International Roadcheck Results
Vehicle out-of-service rate and the leading violation categories.
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8
ATRI — 2026 Operational Costs of Trucking
The 8.6% rise in repair and maintenance costs in 2025.
Written by
Gabriel Gonzalez
Chief Revenue Officer, Simplex Group
Chief Revenue Officer at Simplex Group, with more than 22 years at the company, including nearly 16 years as Chief Operating Officer. His background combines revenue strategy with deep operational experience, giving him a strong perspective on how compliance, risk, permits, cash flow, and operational readiness affect a carrier's ability to grow profitably.
Published · Updated
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Catch it in your yard, not at the roadside
Every limit on this checklist is published. Measuring against them at each service turns a roadside out-of-service order into a scheduled repair.
If you want help setting up the checklist, the vehicle files, or the annual inspection tracking behind it, talk to our team.