Reading Tire Wear: What the Tread Is Telling You

A tire wears the way it does for a reason, and the reason is almost never the tire. Pressure, alignment, a loose wheel end, a bad shock, a dragging brake. The tread records all of it. A driver who can read that record on a walkaround catches a mechanical problem months before it costs a tire, and a fleet that reads it catches a problem before it costs a set.

Here are the common wear patterns on heavy truck and trailer tires, what each one means, and what to do about it.

Both shoulders worn, center fine

Underinflation. The tire is flexing at the shoulders and the center is not carrying its share. This is the most common pattern on trailer tires because trailer tires get checked least. It is also the pattern that leads to the sidewall blowouts we wrote about in Tire Pressure, Heat, and the Blowouts Nobody Sees Coming. Fix the pressure, find out why it was low, and check the mate on a dual.

Center worn, shoulders fine

Overinflation, or a tire running lighter than its rated load on the correct pressure for a full load. The center is crowned and carrying everything. It is common on empty-running trailers and on drive tires set to the loaded pressure on a truck that mostly runs light. The fix is to set pressure to the load actually being carried, per the tire maker's load and inflation table.

One shoulder worn

On a steer tire, this is camber or, more often on a heavy truck, a bent axle or worn kingpins. On a trailer tire, it is axle alignment, a bent axle, or a spring or hanger problem that is letting the axle sit crooked. On a dual, if only the inner or outer tire has the wear, look at the wheel and the spacing. One-shoulder wear on a trailer axle that has been in a curb or a pothole should send you to an alignment check before you buy tires.

Feathering: sawtooth edges across the tread

Run your hand across the tread. If the tread blocks are sharp on one edge and rounded on the other, the tire is being dragged sideways. That is toe, on a steer axle, or a trailer axle that is not tracking square to the frame. It scrubs tires fast and it is worth fixing quickly. On a tractor, it shows up as a pull or a wheel that is off center.

Cupping and scalloping

Dips worn around the tread in a repeating pattern. The tire is bouncing and hitting the road hard at intervals. Causes are a worn shock absorber, a loose or worn wheel bearing, a bent wheel, a tire out of balance, or a loose wheel end letting the tire wobble. On a steer axle, cupping on one side is a wheel end that needs to be looked at now, not later, because the same looseness that cups a tire is what precedes a wheel-end failure.

Cupping on a steer tire is a wheel end or suspension problem until proven otherwise. Do not just replace the tire and move on.

Flat spots

One patch of tread worn flat, sometimes down to the belts. A brake locked that wheel and the tire skidded. It happens on trailers with a dragging or grabbing brake, on tractors with an ABS fault, and on any wheel with a brake that did not release. A single flat spot means the brake needs to be checked. Multiple flat spots around the tire means the wheel is locking repeatedly. Either way the tire may be ruined; belts that show through are a scrap tire.

Diagonal wear on drive tires

Diagonal or heel-and-toe wear on drive tires, where the tread blocks wear on an angle, often comes from a tandem that is out of alignment with itself or with the frame. It can also come from a worn torque rod bushing that lets the axle walk under power. A tandem alignment check and a look at the suspension bushings is the fix.

Rapid wear on one tire of a dual

If one tire in a dual set is wearing much faster than its mate, they are not the same size. Mismatched tread depth, a different tire model, or a pressure difference between the two. The bigger tire carries more load and wears faster, and the smaller one scrubs. Duals should be matched in size, model, and pressure. We covered the economics in Used vs New Truck Tires, and matching duals is one of the reasons a used tire has to be chosen carefully.

What the crew does on site

Read the wear on every tire, check pressures against the load, and look at the mechanical cause: bearings, kingpins, shocks, brakes, suspension bushings. Tires get replaced or moved as needed on site, and the mechanical fault gets fixed or flagged. The point is not to sell tires. It is to stop the truck from eating them. See tire service for what the truck handles and our fleet tire management post for how to build the walkaround into a routine.

Frequently asked questions

How much tread does a steer tire need?

The federal minimum for steer tires is greater than for drive and trailer tires. Any steer tire close to the minimum, or with uneven wear, should be replaced before an inspection finds it.

Can I rotate tires on a semi?

Yes, and moving tires between positions to even out wear is common, especially flipping trailer tires to reverse shoulder wear. Just never move a worn drive or trailer tire to a steer position.

Does wheel balancing matter on a heavy truck?

On steer tires, yes. An out-of-balance steer tire cups and shakes the whole truck. Drive and trailer positions are more forgiving.

The wear is even but fast. What is that?

Load, heat, and the route. Heavy loads on hot pavement at speed wear tires evenly and quickly, and a soft compound tire on a hard-running truck does the same. That is a tire choice question more than a mechanical one.

If the tires are telling you something and you want a second opinion, call Duckett Roadside Repair at (850) 495-0366. Dispatch is answered 24 hours a day and the crew comes to the truck, in the yard or on the road.