The tire requirements in 49 CFR 393.75 set the minimum condition every tire on a commercial motor vehicle must meet to operate legally in interstate commerce. The rule prohibits four specific defects outright, fixes minimum tread depths for steering and non-steering positions, requires tires to be inflated and loaded within their marked ratings, restricts certain regrooved and speed-rated tires, and applies to every bus, truck, truck tractor, and trailer covered by the Federal Motor Carrier Safety Regulations. A single violation can place the vehicle out of service on the spot and carries a civil penalty ceiling of $19,246.
Four Tire Defects That Put a Vehicle Out of Service
The regulation prohibits operating a commercial motor vehicle on any tire that has:
- Body ply or belt material exposed through the tread or sidewall
- Tread or sidewall separation
- A flat tire or an audible air leak
- A cut deep enough to expose the ply or belt material
Any one of these conditions fails a North American Standard Level I roadside inspection and puts the vehicle out of service until the tire is replaced or repaired.1eCFR. 49 CFR 393.75 – Tires2Commercial Vehicle Safety Alliance. All Inspection Levels Each of these four defects carries a severity weight of 8 out of 10 under FMCSA’s Safety Measurement System, among the highest weights assigned to any vehicle maintenance violation.
Minimum Tread Depth
Tread depth minimums depend on where the tire sits on the vehicle:
- Front wheels of any bus, truck, or truck tractor: at least 4/32 of an inch in every major tread groove
- All other tire positions, including drive and trailer axles: at least 2/32 of an inch in every major tread groove
The stricter front-axle number reflects the greater tread depth steering tires need to keep directional control, especially on wet pavement.1eCFR. 49 CFR 393.75 – Tires
How the Measurement Has to Be Taken
Readings must come from a major tread groove, and the regulation specifically excludes measurements taken at tie bars, humps, or fillets. Those are the small molded features inside the groove that would give an artificially high reading. Press a standard tread depth gauge into the deepest part of the groove, away from those features.1eCFR. 49 CFR 393.75 – Tires
Inspectors do not average readings. The worst single reading in any major groove controls, and both the 4/32″ front-position and 2/32″ other-position violations carry a severity weight of 8.
Load Rating and Inflation
A commercial vehicle cannot run on tires loaded beyond the weight rating marked on the sidewall. Where a sidewall marking is missing, the limit comes from the tire load tables under Federal Motor Vehicle Safety Standard No. 119. States may issue a special permit that allows overloaded tires, but the vehicle’s speed under that permit can never exceed 50 mph.3eCFR. 49 CFR 393.75 – Tires
Load ratings differ between single and dual configurations, so a tire’s rating in a dual pair may not match its single-position rating. Check both the sidewall marking and the actual axle weight before a trip.
Cold Inflation Pressure and the Roadside Correction
Every tire must carry a cold inflation pressure at or above the pressure specified for the load it is carrying. Because roadside checks happen with warm tires, the regulation lets inspectors estimate the cold pressure by subtracting a heat buildup factor from the measured pressure. For a vehicle that averaged 41–55 mph in the hour before the check:
- Tires rated at 4,000 pounds or less: subtract 5 psi from the measured pressure
- Tires rated above 4,000 pounds: subtract 15 psi from the measured pressure
If the estimated cold pressure still falls below the required minimum for the load, the tire is in violation.1eCFR. 49 CFR 393.75 – Tires The 15 psi correction for heavy-rated tires is wider than most drivers expect, so pressures are best checked before the truck moves for the day.
Speed-Restricted Tires
Some commercial tires are rated for a maximum speed of 55 mph or less. Those tires must carry a sidewall label in the FMVSS No. 119 format, reading “Max speed ____km/h (____mph).”4eCFR. 49 CFR 571.119 – Standard No. 119; New Pneumatic Tires for Motor Vehicles A vehicle equipped with speed-restricted tires cannot legally exceed that printed speed, even where the posted road speed is higher.3eCFR. 49 CFR 393.75 – Tires The speed limit follows the tire, not the road, and exceeding it carries a severity weight of 8.
Regrooved, Recapped, and Retreaded Tires
The rules differ sharply between buses and other vehicles.
On the front wheels of a bus, no regrooved, recapped, or retreaded tire may be used at all. That is a total ban on refurbished rubber in the steering position of any passenger-carrying vehicle.1eCFR. 49 CFR 393.75 – Tires
On the front wheels of a truck or truck tractor, only regrooved tires with a load rating of 4,920 pounds (2,232 kg) or more are prohibited. A regrooved tire with a lower load rating may go on the front axle. Section 393.75 does not specifically ban recapped or retreaded tires from truck front axles, though many carriers ban the practice by company policy.1eCFR. 49 CFR 393.75 – Tires Retreads on drive and trailer axles are common and legal.
A regrooved tire has had new tread channels cut into its existing rubber. A recapped or retreaded tire has a new layer of rubber bonded onto the old casing.
Manufactured Homes: A Separate Rule
Tires used to transport manufactured homes follow their own loading rules. Homes built and labeled before January 1, 2002 may move on tires overloaded by up to 18 percent above the sidewall rating, but any overload above 9 percent caps transport speed at 50 mph. Homes built on or after that date get no overload allowance.3eCFR. 49 CFR 393.75 – Tires The allowance applies only during the transport move itself.
What a Violation Costs
Three consequences stack on a single tire violation.
First, the out-of-service order. Any of the four prohibited defects, or a tread depth reading below the minimum, keeps the vehicle where it sits until the tire is fixed.
Second, the Safety Measurement System hit. Violations feed into the Vehicle Maintenance BASIC with a severity weight assigned to each type:
- Severity 8: exposed cord, tread or sidewall separation, flat or audible leak, cuts exposing belt material, front tread below 4/32″, other tread below 2/32″, regrooved or recapped tires on a bus front axle, and exceeding a speed-restricted tire’s rated limit
- Severity 3: regrooved tire on a truck front axle, overloaded tires, and underinflated tires
A violation that also triggers an out-of-service order adds 2 points on top of the base weight, so a single serious tire defect can hit the maximum of 10. Accumulated points push the carrier’s Vehicle Maintenance percentile toward FMCSA’s intervention thresholds and can lead to warning letters, targeted inspections, or a compliance investigation.
Third, the civil penalty. Each violation of FMCSA safety regulations can carry a penalty of up to $19,246 after inflation adjustments.5Federal Register. Revisions to Civil Penalty Amounts, 2025 That ceiling comes from the $10,000 statutory base at 49 U.S.C. § 521(b)(2)(A), adjusted annually.6Office of the Law Revision Counsel. 49 USC 521 – Civil Penalties Actual assessments vary with the severity of the violation, the carrier’s history, and whether the defect contributed to a crash. Multiple bad tires on the same vehicle generate multiple violations.
Driver Reporting Ties to the Tires
Tires are one of the eleven components a driver must cover in the daily vehicle inspection report under 49 CFR 396.11. At the end of each day, the driver must document any defect that could affect safe operation; if none exist, no report is required.7eCFR. 49 CFR 396.11 – Driver Vehicle Inspection Reports The next driver must review the most recent report and sign to acknowledge that any listed defects have been repaired.8eCFR. 49 CFR 396.13 – Driver Inspection
That paperwork trail matters after a crash. If a post-trip report flagged a bulging sidewall that was never repaired, both the driver who signed off the next morning and the carrier that failed to act are exposed.
Challenging a Tire Violation
A carrier that believes a roadside tire violation was recorded in error can file a Request for Data Review through FMCSA’s DataQs system. A successful challenge removes the violation from the carrier’s SMS record and drops the Vehicle Maintenance score accordingly. The realistic openings are factual errors, such as a tread depth reading taken at a tie bar or a violation coded to the wrong axle position. Disagreement with the inspector’s judgment, on its own, rarely wins, because inspectors document defects with photographs and measurements.