By Norman Ford · Updated October 2026
Semi truck tires: positions, rules, sizes and cost
Tires are the only part of the truck that touches the road, and one of its largest running costs. They are also among the most common reasons trucks are cited at inspections. Most tire trouble comes down to a few basics: the right tire on the right position, the right pressure for the load, and replacing tires before they become a problem.
Tire positions on a tractor-trailer
Drag the slider to pull a wheel end apart and see what sits behind the tire. Tap each part for what to check.
Tap a numbered balloon for the part's job, check and spec.
| ITEM | PART | WHAT IT DOES | CHECK |
|---|---|---|---|
| 1 | Tire | Carries the load, provides grip and absorbs bumps. Steer, drive and trailer tires are built differently. | Tread depth, pressure, cuts, bulges and uneven wear. |
| 2 | Wheel | Steel or aluminum, mounted to the hub with studs and nuts. | Cracks, damaged stud holes, rust trails from loose nuts. |
| 3 | Brake drum | The braking surface on drum brakes, turning with the wheel. | Cracks, heat checking and wear. |
| 4 | Hub | Carries the wheel and turns on the bearings. | Hub oil level and seal leaks. |
| 5 | Bearings | Let the hub turn smoothly on the spindle. | Excess play or noise. |
| 6 | Spindle | The end of the axle that the hub turns on. | Inspected by a technician when the hub is off. |
- Steer tires sit on the front axle. They are usually rib-tread tires designed for precise handling and even wear. A steer tire failure is the most dangerous kind, so they deserve the most attention.
- Drive tires sit on the tractor's drive axles and put power to the road. They usually have deeper, lugged treads for traction. Our guide to the best drive tires for a semi truck compares what to look for.
- Trailer tires carry the load and get scrubbed in tight turns. They are built for sidewall protection and even wear.
Federal tire rules
Under 49 CFR 393.75, a tire on a commercial motor vehicle may not be used if it has fabric exposed through the tread or sidewall, a tread or sidewall separation, a flat or an audible leak, or a cut that exposes the ply or belt material. Minimum tread depth is 4/32 inch on the steer tires of a truck or truck tractor and 2/32 inch on other positions, measured in a major tread groove.
Source: 49 CFR 393.75, checked October 2026
Tires also must not be loaded beyond the load rating molded on the sidewall for the pressure used.
Sizes and load ranges
Truck tire sizes are molded on the sidewall. A size such as 295/75R22.5 gives the width in millimeters, the sidewall height as a percentage of width, radial construction and the wheel diameter in inches. The load range or ply rating shows how much the tire can carry at a given pressure. Always match the size and load range your truck's maker specifies.
Wheels matter too: steel and aluminum wheels have different weights, and the wheel must match the tire size and the hub. Our guide to semi truck wheels covers wheel types, sizes and care.
Pressure for the load
Tire makers publish load and inflation tables showing the right pressure for the weight each tire carries. Underinflation is the leading cause of tire failures: it builds heat, wears tires faster and burns more fuel. Check pressures cold, with a calibrated gauge, and adjust them for the load you carry and the season.
How many tires does a semi truck have?
A standard five-axle tractor-trailer has 18 tires:
- 2 steer tires
- 8 drive tires in four dual pairs
- 8 trailer tires in four dual pairs
Wide-base single tires replace each dual pair with one wider tire. They save weight and can improve fuel economy, but a single flat leaves no partner tire to carry the load.
Retreads
Retreading puts new tread on a sound used casing. It is common on drive and trailer positions and can lower tire cost per mile a lot. Casing quality decides how many retreads a tire can take. Federal rules restrict regrooved tires on the front wheels of trucks and truck tractors when the tire's load capacity is 4,920 pounds or more, and many owners keep new tires on the steer axle.
Cost and cost per mile
Truck tire prices vary by brand, position and size. What matters more than the price of one tire is the cost per mile over its life, including retreads. The tire cost per mile calculator works it out from your prices and mileages.
Mounting and service
Mounting and inflating truck tires is dangerous work. Shops use tire machines and restraining cages to do it safely; our guide to the semi truck tire machine explains the equipment. Leave mounting to trained technicians.
When a tire fails or a wheel end has problems, our guide to semi truck repair covers when to call a shop and how to choose one.
Daily tire checks
- Look at every tire at each stop: cuts, bulges, objects in the tread, low tires.
- Check pressures cold with a gauge, not by thumping.
- Check that duals are not touching and have no debris between them.
- Watch for oil on the wheel, a sign of a leaking hub seal.
- Look for rust trails around lug nuts, a sign of a loose wheel.
Tires by type of work
The right tire depends as much on the work as on the position:
- Long haul: fuel-efficient steer and drive tires, often low rolling resistance lines, with casings designed for retreading.
- Regional and city work: tires that resist scrubbing from tight turns and curb damage.
- Construction and dump work: tires with cut and chip resistant treads and tough casings for job sites.
- Winter routes: drive tires with strong snow traction, and chains where required.
Our guide to truck tire brands explains how to compare makers on these points.
Tire age and storage
Tires age even when they are not used. Rubber hardens and can crack over time, especially in sun and heat. The DOT code on the sidewall ends with four digits showing the week and year the tire was made. Check it when buying, including on spares and retreads, and inspect older tires closely for cracking in the sidewall and between the tread blocks. Store spare tires out of direct sunlight, away from heat and ozone sources such as electric motors.
Alignment and tire wear
A truck that is out of alignment can wear out steer and drive tires much faster than normal. Signs include wear on one shoulder, feathered edges on the tread ribs, and a truck that pulls to one side. Have alignment checked when you see uneven wear, after replacing steering or suspension parts, and after a hard hit on a curb or pothole.
Where we fit
We are a dispatch desk for 26 ft box trucks and larger, not a tire seller. We plan loads around your service days. Learn more about our dispatch service.