In short. Each wear pattern points to a family of causes: both edges worn means under-inflation, the centre worn means over-inflation, one edge only means camber or toe out of the car maker's specification, feathered ribs mean toe, scooped patches (cupping) mean worn shocks, an unbalanced or a bent wheel, and a single flat patch means hard braking or a car left standing too long. Find and fix the cause before fitting new tyres, or they wear the same way. Then check the law where the tyre is most worn: in the UK, 1.6 mm across the central three-quarters of the tread, so an edge may be bald and still pass, but exposed cord anywhere is illegal.
The patterns at a glance
This table is ours: we read five makers' pages side by side on 16 October 2026 and kept, for each pattern, what they say causes it. Where they disagree, the next sections say so.
| What you see | Usual name | Causes the sources give | First check | Sources |
|---|---|---|---|---|
| Both shoulders worn, centre less worn, tread looks rounded | Edge wear, shoulder wear | Under-inflation; load carried on the edges, tyre flexes and runs hot | Pressure, cold, against the car maker's figure; look for a slow leak | Michelin AU; Michelin US; Goodyear US; Monroe |
| Centre worn more than both edges | Centre wear | Over-inflation; a little centre wear on rear tyres can be how the car is set up | Pressure, cold | Michelin AU; Michelin US; Goodyear US; Monroe |
| One edge only, inside or outside | One-sided shoulder wear, camber wear | Camber out of specification (negative wears the inside, positive the outside); worn bushes or dampers; hard cornering | Alignment check; suspension inspection | Michelin AU; Bridgestone US; Goodyear US |
| Tread ribs smooth on one side, sharp on the other | Feathering, sawtooth | Toe out of specification, sometimes with caster | Alignment check (toe) | Bridgestone US; Michelin US; Goodyear US |
| Each tread block worn more on one side, around the tyre | Heel/toe wear | Excessive toe (Bridgestone); hard driving and too little rotation (Goodyear) | Alignment check, then rotation | Bridgestone US; Goodyear US |
| Dips or scoops spaced around the tread, rhythmic noise | Cupping, scalloping | Worn shocks or struts, unbalanced tyre, bent wheel, misalignment, wrong pressure | Shocks, balance, wheel run-out, alignment | Goodyear US; Monroe; Michelin AU; Michelin US |
| One smooth patch in one place | Flat spot | Hard braking; car standing too long | Brakes; the tyre itself | Goodyear US; Monroe |
| Wear running at an angle across the tread | Diagonal wear | Misalignment with worn suspension or bushes | Full alignment and suspension check | Goodyear US |
| Patchy wear in no regular order | Sporadic wear | Worn ball joints, tie rod ends, control arms, bushes or wheel bearings | Steering and suspension inspection | Monroe; Michelin AU |
Two things the table cannot show. A pattern on one tyre points to that corner (its pressure, its wheel, its suspension); the same pattern on both tyres of an axle points to something shared, such as the axle's alignment. And no wear does not mean no problem. Hunter Engineering, which makes alignment equipment, reports a 100,000-vehicle study in which 13% of cars showed irregular tyre wear, while 44% failed the alignment check without showing tyre wear yet (Hunter Engineering, Quick Check).
Both edges worn: the tyre ran soft
Michelin Australia explains the mechanism: when a tyre is under-inflated, the centre of the contact patch is not properly supported and the load moves to the shoulders, which wear faster; the tyre also flexes too much, runs warmer than normal and raises fuel consumption (Michelin AU, irregular wear). Michelin US adds that the extra heat reduces durability and can lead to tyre failure. Monroe adds that a car that tows or carries heavy loads needs the pressure adjusted for the load (Monroe).
Use the car maker's figure, from the door pillar label or the handbook, checked cold at least once a month; our tyre pressure guide explains where to find it. If one tyre alone shows edge wear, suspect a slow leak in that tyre or its valve: see slow punctures.
Centre worn: too much pressure
With too much air, the centre of the tread carries most of the load and wears faster than the edges (Michelin AU, Michelin US, Goodyear US, Monroe). Michelin US asks you to check pressure cold, or at least three hours after driving. Michelin Australia adds a nuance most charts leave out: a small amount of centre wear, on rear tyres for example, can be a characteristic of the way the car maker set the car up. It is still worth a pressure check.
One edge only: inner or outer tyre wear
When only one shoulder is worn, the makers look first at the alignment. Michelin Australia defines camber as the tilt of the wheel from the vertical seen from the front: positive camber (top of the wheel leaning out) wears the outer edge, negative camber (top leaning in) wears the inner edge, and too much difference between the two front wheels makes the car pull (Michelin AU, alignment and balancing); other causes of a pull are in why a car pulls to one side. Bridgestone calls this "camber wear" and puts it down to excessive positive or negative camber (Bridgestone US). Michelin Australia also names suspension parts, bushes and dampers in poor condition, and Goodyear adds hard cornering.
Inside-edge wear is the one people miss, because it is hidden from view. Michelin Australia says the camber angle is studied and set for each vehicle to keep the tyre as flat as possible in a straight line and in corners; our reading is that a slightly more worn inner edge can therefore come from the car maker's own setting rather than a fault. Only a measurement against the maker's specification for that model tells the two apart; we give no figures for any car here.
The road itself plays a part, and it depends on the country. Michelin Australia explains that the road slopes towards its edge and the driver steers slightly against that slope, which wears one tyre more: in countries that drive on the left, the right tyre; in countries that drive on the right, the left tyre. Applied to our four countries, that means slightly more wear on the right-hand tyres in the UK and Australia, and on the left-hand tyres in the US and Canada. A small difference of that kind is normal; a large one is not.
A kerb strike or a pothole can move the alignment. Michelin Australia lists both among the causes of misalignment, and Hunter Engineering says most car makers recommend an alignment check every 10,000 miles or 12 months, whichever comes first, and whenever you notice irregular tyre wear, handling problems or a crooked steering wheel (Hunter Engineering).
Feathering and sawtooth wear: toe
Run your hand across the tread. If the ribs feel smooth when you slide one way and sharp the other way, the tyre is feathered. Bridgestone describes it as ribs "worn lower/smoother on one side and higher/sharper on the other", often caused by a combination of excessive toe and caster. Michelin US says a misaligned car gives the tread edges a sawtooth or feathered look, caused by erratic scrubbing against the road, and that the car most likely needs a toe correction (Michelin US, sawtooth or feathered edges).
Heel/toe wear is close: each block, around the tyre, is worn more on one side, and it feels like saw teeth. Here the makers do not agree on the cause. Bridgestone says it typically occurs in a shoulder rib and is often caused by excessive positive or negative toe; Goodyear's table puts it down to aggressive driving and poor rotation habits.
Cupping, or scalloping
Cupping is a series of worn patches spaced around the tyre. Goodyear says they often appear three to four inches apart, that the driver may first feel a vibration in the steering wheel, and that in extreme cases the tyre seems to bounce on the road (Goodyear US, tire cupping). Michelin Australia describes a rhythmic growling noise that grows with speed (Michelin AU, scalloping).
The causes the makers give differ, and the difference matters:
| Source | Causes of cupping it names |
|---|---|
| Goodyear US | Misalignment; worn suspension and shocks or struts that let the wheel bounce; unbalanced tyres or bent wheels |
| Monroe | Worn shocks and struts that let the tyre leave the road; unbalanced wheels or worn suspension parts |
| Michelin AU | Misalignment, worn suspension, unbalanced tyres, incorrect pressure |
| Michelin US | Two symptom pages: "Cups" points to worn parts, wheels out of balance or suspension and steering parts needing service; "Scalloped" gives poor alignment |
Our reading: anything that makes the wheel bounce or wobble can produce cupping. A damper that no longer controls the wheel is the cause most sources share; balance and a bent wheel come next. How to tell a worn damper is in worn shock absorbers: symptoms and test. Monroe adds that on many newer cars with advanced suspension geometry, worn dampers may show as faster overall wear rather than classic cupping. Goodyear is clear about the tyre: cupping will not correct itself, the cause must be fixed first, and the tyre may need replacing because the dips have reduced the tread depth in places.
When the wheel is the culprit
Most wear charts stop at pressure and alignment. Three makers' pages also point at the wheel:
- A bent wheel. Monroe says a pothole can bend or crack a steel or aluminium rim, making the tyre vibrate and wear irregularly; a wheel inspection tells you. Who pays for pothole damage in England and Wales is in our pothole claim guide. Goodyear lists "unbalanced tires or bent wheels" among the causes of cupping.
- Balance. Michelin Australia says an imbalance causes vibrations at certain speeds and accelerates tread wear, that balancing is needed every time a tyre is fitted, and that a wheel hit by a kerb may need rebalancing. Goodyear adds: at the first sign of vibration, and once a year. A balancing weight cannot correct a bent wheel: see our wheel balancing guide.
- Damage after a kerb strike. A bulge on the sidewall or a crack in the rim is a different case from wear. The MOT manual lists a tyre with "a lump, bulge or tear caused by separation or partial failure of its structure" as a dangerous defect (5.2.3 (d)(ii)): do not drive on it, and see sidewall bulges. What can and cannot be repaired on an alloy wheel is in our alloy wheel repair guide.
Changing wheels does not correct the geometry of a car. Onyx Forged does not recommend a size or an offset: the car maker's documents and your tyre fitter decide what goes on the car, and our tyre size calculator only compares the dimensions. How the sidewall markings read is in how to read a tyre size.
Flat spots and patchy wear
A single smooth patch in one place is a flat spot. Goodyear gives two causes, hard braking and a car standing still too long; Monroe links abrupt braking to "flat-spotting", excessive tread loss on a concentrated area. A flat spot is a reason to have the brakes checked, and the tyre too. Patchy, irregular wear may point to the suspension, says Michelin Australia, with bushes or dampers in poor condition; Monroe lists the parts that hold the wheel in position and, once worn, cause uneven wear: ball joints, tie rod ends, control arms, their bushes, wheel bearings.
When uneven wear makes a tyre illegal
Uneven wear reaches the limit in one place first, so read the rule where the tyre is most worn.
| Country | Rule for a car tyre | Text and date |
|---|---|---|
| UK (Great Britain) | At least 1.6 mm "throughout a continuous band comprising the central three-quarters of the breadth of tread and round the entire outer circumference"; no ply or cord exposed; no lump, bulge or tear | Road Vehicles (Construction and Use) Regulations 1986, reg. 27(1) and 27(4)(f), the 1.6 mm rule in force from 1 January 1992 (legislation.gov.uk); MOT inspection manual, 5.2.3, updated 14 October 2026 |
| US | No federal tread rule for private cars; states set it. California: at least 1/32 in (0.79 mm) "in any two adjacent grooves at any location of the tire". Bridgestone says most states use 2/32 in (1.59 mm). Commercial vehicles: 4/32 in (3.18 mm) on the front tyres of buses and trucks, 2/32 in on the others | California Vehicle Code 27465 (text); 49 CFR 393.75 (eCFR) |
| Australia | "Except at the tread wear indicators, tyres must have a minimum tread depth of 1.5mm in all principal grooves"; no tread wear indicator may touch the road; less than 1.5 mm in the shallower secondary grooves does not make the tyre unroadworthy | Victoria, Vehicle Standards Information 16, October 2021 (PDF); other states publish their own notes |
| Canada | Provincial. Ontario: not worn so that, in any two adjacent major grooves at three equally spaced points, the wear indicators touch the road or less than 1.5 mm remains. Quebec: tread "must never be less than" 1.6 mm | Ontario Reg. 625, s. 3(1) (e-Laws); SAAQ, last updated 23 July 2026 (SAAQ) |
What the British rule means for an edge worn bald. The MOT manual says it in so many words: either side of the central three-quarters "can be devoid of tread ('bald')". Our example, with an invented figure: on a tread about 180 mm across, the central three-quarters is 135 mm, which leaves 22.5 mm on each side outside the 1.6 mm rule. An inner shoulder worn by camber sits exactly there. The tyre can be legal on tread depth while that edge is down to nothing, but the moment the cords show, it is illegal (reg. 27(1)(e)) and a dangerous MOT defect. Michelin Australia makes the same point for shoulders without wear guides: there, the requirement is simply that the tread is not slick. If you can see cords or wire on any part of a tyre, do not drive on it: have the wheel changed for the spare or the car recovered, and have the tyre checked before you go back on the road.
What else the MOT looks at. Section 5.3.2 rejects a shock absorber with "negligible damping effect" (major). The tyre defects in 5.2.3 cover depth and damage, not "uneven wear" as such, so a cupped or feathered tyre can pass and still need attention.
What to do, in order
- Look at all four tyres, and the spare. Note where the wear sits and whether the pair on the axle matches. Turn the steering to full lock to see the inside shoulder; to get under the car, raise it and rest it on axle stands, never on the jack alone.
- Measure the depth in the main grooves, inside, centre and outside, with a gauge. A difference between inside and outside on one tyre is the clearest sign of a camber or toe problem.
- Check the pressure cold against the car maker's figure. Two of the nine patterns in our table are pressure alone.
- Run your hand across the tread for feathering, and listen for a rhythmic growl at speed for cupping.
- Have the cause found: an alignment check for one-sided wear and feathering; dampers, balance and the wheel itself for cupping; brakes for a flat spot; steering and suspension joints for patchy wear.
- Then deal with the tyres. Replace any that are at the legal limit, damaged or badly cupped. Rotating helps even out wear only after the cause is fixed: Goodyear asks for misalignment and imbalance to be corrected before rotation, and our rotation guide shows what each tyre allows.
Frequently asked questions
What causes tyres to wear on the inside edge?
Mostly negative camber or toe out of specification, and worn suspension parts. Camber is set for each car by its maker, so a slightly more worn inner edge is not always a fault; an alignment measurement against the maker's figures decides.
What causes wear on the outside edge of a tyre?
Both shoulders worn means under-inflation; the outer edge alone points to positive camber or hard cornering. The road's slope also wears the right-hand tyres a little more in the UK and Australia, the left-hand ones in the US and Canada.
What does cupping on a tyre mean?
Dips spaced around the tread, usually with a rhythmic noise and some vibration. Goodyear and Monroe name worn shocks or struts first, with an unbalanced tyre or a bent wheel next; Michelin adds misalignment and pressure. The tyre will not recover once cupped.
Can a wheel cause uneven tyre wear?
Yes. A wheel bent by a pothole can make the tyre vibrate and wear irregularly (Monroe), and Goodyear lists bent wheels among the causes of cupping. An unbalanced wheel and tyre assembly also speeds up wear (Michelin). A balancing weight does not fix a bent wheel.
Can I keep driving on unevenly worn tyres?
Only while the tyre is within the legal limit, with no cord showing and no bulge; the wear continues until the cause is fixed. With visible cords or a bulge, do not drive on it: fit the spare or have the car recovered, and have the tyre and wheel checked before you go back on the road. A steering vibration or a growl that grows with speed is also a reason to have the car checked soon.
Is a bald edge an MOT failure?
Not by itself. The 1.6 mm rule applies to the central three-quarters of the tread, and the MOT manual says the sides outside it can be bald. Exposed ply or cord anywhere is a dangerous defect.
Will rotating my tyres fix uneven wear?
No. Goodyear says to correct misalignment, imbalance or other mechanical problems before rotating.
Where to go next
Onyx Forged is a French brand of made-to-order forged wheels, designed to JWL/VIA standards; the tyres, their fitting, balancing and the alignment stay with your tyre fitter. See how to customise a set.
Sources
- Tyre makers: Michelin Australia, irregular tyre wear, wheel alignment and balancing and tyre scalloping; Michelin US, sawtooth or feathered edges, cups and the related symptom pages; Bridgestone US, tire tread wear causes; Goodyear US, tire wear patterns and tire cupping.
- Suspension and alignment: Monroe, why do tires wear unevenly?; Hunter Engineering, Quick Check and benefits of wheel alignment.
- UK: Road Vehicles (Construction and Use) Regulations 1986, regulation 27; GOV.UK, MOT inspection manual, section 5.
- US: California Vehicle Code 27465; 49 CFR 393.75.
- Australia: Victoria, Vehicle Standards Information 16.
- Canada: Ontario Reg. 625; SAAQ, winter tires.
All pages were read on 16 October 2026.
The Onyx Forged design office.