Tyre Outer Edge Wear: Uneven Wear Patterns Chart 2026

Uneven tyre (tire) wear patterns at a glance

Tyre outer edge wear on both shoulders almost always means the tyre has been running underinflated. Wear on only one shoulder points to alignment (camber or toe) or hard cornering. Find and fix the cause before fitting new tyres, or they will wear the same way. If any part of the tread has reached the wear indicators, replace the tyre.

💡 Check yours: Tyre Wear Calculator. Enter your tread readings to see how much usable tread is left.

Why tyres wear unevenly

A tyre wears evenly when its whole contact patch carries the same load. Anything that pushes load onto one part of the tread wears that part faster:

• Pressure changes the shape of the contact patch. With too little air the shoulders carry the load. With too much, the centre does.
• Alignment decides the angle at which the tyre meets the road. Camber tilts the tyre in or out, so one shoulder wears. Toe points the tyre slightly sideways, so it scrubs as it rolls and the blocks feather.
• Suspension and balance decide whether the tyre stays pressed evenly on the road. A worn damper or an unbalanced wheel lets the tyre bounce, and each landing wears a patch. That is how cupping forms.
• Driving style matters too. Fast cornering wears the outer shoulders, and hard braking with locked wheels grinds flat spots. In a 1996 decision, NHTSA said ABS should in theory stop tyres flat-spotting because it prevents wheel lockup.

Tyre outer edge wear: one edge or both?

Start by checking whether the wear is on one shoulder or both, and on how many tyres.

Both outer edges on the same tyre. This is the classic sign of underinflation. A soft tyre sags in the middle, the shoulders take the load, and they wear first. Check pressures cold with a gauge and set them to the vehicle’s figures. NHTSA says to find these on the Tire and Loading Information label on the driver’s door edge or post, or in the owner’s manual. Do not use the maximum printed on the sidewall. The tyre pressure guide explains how to set them.

Only the outer edge, on one or both front tyres. This points to alignment, usually camber or toe, or to cornering hard on winding roads. If only one front tyre is affected, the car may have hit a kerb or pothole and bent a suspension part.

Only the inner edge. This is easy to miss because you cannot see it from outside the car. Run your hand across the full width of the tread, or turn the steering to full lock to look. Inner-edge wear is usually caused by alignment, not pressure.

How worn is too worn?

The limit applies to the most worn part of the tread, not to the average. A tyre with deep grooves in the centre but a bald outer shoulder is worn out.

• US: NHTSA says tyres are not safe and should be replaced when the tread is worn down to 2/32 inch. Its vehicle-in-use standard, 49 CFR 570.9, sets the same minimum for cars and other light vehicles. States apply it through their own laws.
• Wear indicators: under 49 CFR 571.109, every passenger tyre made on or after 1 August 1968 must have tread wear indicators that show when the tread is down to 1/16 inch. That is the same depth as 2/32 inch. NHTSA notes that early research found treads behave like bald tyres at about that depth. When the tread is level with an indicator bar at any point, the tyre is due for replacement.
• UK, Canada and Australia: the legal minimum is set by national, provincial or state rules, so check the local rule. On a tyre with uneven wear, the worn edge is where it will fail first.

Measure in several grooves across the width and at a few points around the tyre. Gauges read in millimetres or in 32nds of an inch. NHTSA’s penny test is quick but rough: put a penny in the groove with Lincoln’s head upside down and facing you. If you can see the top of his head, it is time for new tyres. On a tyre with uneven wear, do this in the shoulder groove, not only the centre.

How often to check

NHTSA says to check the tread at least once a month when you check the pressure. Its maintenance list covers pressure, tread wear, damage, rotation, balancing and alignment. It also says to look at the tread when you rotate the tyres and before long trips. Uneven wear builds up slowly, so a monthly look usually catches it while the tyre can still be saved.

Rotate, align or replace?

Work through these in order:

1. Replace now if any groove has reached the wear indicators, cords or steel show through, or there is a bulge or cut. For sidewall damage, use the sidewall damage guide.
2. Fix the cause before buying tyres. Wear on one edge or feathering needs an alignment check. Cupping needs the dampers and suspension joints checked and the wheels balanced. Wear on both shoulders, or in the centre, needs the pressure corrected and then checked monthly.
3. Rotate if the tyres are worn but still legal. Moving tyres between positions spreads the wear, but only after the fault is fixed. Use the interval in your owner’s manual. Rotation patterns and when to align are covered in the tyre rotation and alignment guide.
4. Keep watching cupped or flat-spotted tyres. These shapes do not even out once formed. If the tyre stays noisy or vibrates after balancing, replace it.
5. Fit new tyres in axle pairs where only two are replaced, so both sides of the axle grip and wear the same way.

Sources

• NHTSA: Tires (TireWise), tread depth, monthly checks and maintenance: https://www.nhtsa.gov/vehicle-safety/tires
• NHTSA: Congratulations on Your New Tire Purchase (pressure label, rotation, penny test): https://www.nhtsa.gov/node/35306
• Federal Register, 30 January 1996, NHTSA decision on treadwear indicators (49 CFR 571.109 and 570.9): https://www.govinfo.gov/content/pkg/FR-1996-01-30/html/96-1654.htm