Truck Tire Wear Patterns: Reading What the Tire Is Telling You

The direct answer: a tire wears unevenly because something other than the tire is wrong — pressure, alignment, a bearing, a brake, a mismatched dual — and replacing the tire without fixing that wears the next one the same way. Federally, steer tires need at least 4/32 inch of tread in a major groove and all other tires at least 2/32 inch (49 CFR 393.75), and no tire may run with cord exposed, a separation, a cut to the cord, or an audible leak.

The patterns and what they usually mean

• Both shoulders worn, center good — under-inflation. The tire flexes on its shoulders. Check for a slow leak and the inflation habit.
• Center worn, shoulders good — over-inflation for the load, common on an empty-running trailer set at loaded pressure.
• One shoulder worn — camber, a bent axle or spindle, or on trailers an axle out of alignment. Fast on steer tires, and usually accompanied by pull or wander.
• Feathering (ribs sharp on one edge, rounded on the other, felt by hand) — toe out of specification. Alignment, tie-rod ends, or a worn drag link.
• Cupping or scalloping (dished patches around the tire) — something letting the tire bounce: shocks, a worn wheel bearing, suspension bushings, or imbalance. Often announced by vibration at speed.
• Diagonal or “river” wear across a trailer tire — a trailer axle out of square with the frame, so the tire scrubs sideways down the road. The fix is trailer alignment, and the dog-tracking is visible from the mirror.
• Flat spots — a brake that locked: an out-of-adjustment or grabbing brake, an ABS fault, or a dragging brake on a trailer with no load.
• One dual worn faster than its partner — mismatched diameters or pressures between duals; the larger or harder tire carries the load and wears, the other scrubs.
• Heel-and-toe on drive tires (each lug worn at an angle) — normal to a degree on drive axles; excessive when pressure is low or the duals are mismatched.
• Rapid, even wear on drives — usually duty: heavy torque, grades and loads. Rotation and pressure management are the levers.

Measuring tread correctly

Measure in a major tread groove, not at a tie bar, hump or fillet — the regulation says so and the readings differ. Measure at several points around the tire, because a tire that averages 5/32 can be at 3/32 in one spot and that spot is what an inspector finds. Steer tires are judged at 4/32 inch at any point on a major groove.

The other legal conditions

Beyond tread depth, 393.75 prohibits operating on any tire with body ply or belt material exposed through tread or sidewall, any tread or sidewall separation, a flat or an audible leak, or a cut deep enough to expose cord. Regrooved tires with a load capacity of 4,920 lb or more are prohibited on the steer axle of a truck or tractor, and tires may not carry more weight than the sidewall rating or be run above a speed restriction marked on them.

What a tire inspection here includes

Depth at several points per tire, pressures cold against the load, a hand pass for feathering, a look at the pattern against this list, and a check of what the pattern accuses — bearing play, alignment, brakes, shocks — before recommending the fix. Full scope under tire inspection, repair and replacement.

Common questions

Can I move a worn steer tire to a drive or trailer position?

If it meets the 2/32 minimum and has no cord, separation or repair in a prohibited area, yes — it is a common practice. It cannot go back to the steer axle once below 4/32, and regrooved tires above the weight rating cannot run on a truck’s steer axle at all.

How much pressure difference between duals is too much?

Even a few psi changes the effective diameter enough for one tire to carry more than its share. Check both duals at every fuel stop and match them; the inner dual is the one nobody checks.

Is irregular trailer tire wear really an alignment problem?

Most of the time. A trailer axle that is out of square by a small amount scrubs every tire on it for every mile, and the diagonal pattern is the signature. Alignment is cheap next to a set of trailer tires.

General guidance citing the Federal Motor Carrier Safety Regulations as published on eCFR, reviewed 2026-10-16. It is not legal advice.