Written by the fitting team at 24/7 Mobile Tyre Services, Glasgow. Last reviewed: July 2026.
“Everyone says it’s illegal to mix tyres.” “My garage says it’s fine.”
Both of those are heard constantly, and both are partly wrong. There is a clear line between what the law prohibits and what is merely a bad idea, and once you know where it sits the whole subject becomes simple.
That line is what this page is for.
Quick answer: Fitting different brands, tread patterns or tread depths to the same axle is legal in the UK. Fitting tyres of different construction types, meaning mixing radial and cross ply, is not. Different sizes on the same axle will fail an MOT. Even where it is legal, matching tyres across an axle gives more predictable braking and handling.
The clear answer: legal, illegal, and unwise
| Same axle | Status |
|---|---|
| Different brands | Legal |
| Different tread patterns | Legal |
| Different tread depths | Legal |
| Different construction types (radial with cross ply) | Illegal |
| Cross ply or bias belted at the rear with radial at the front | Illegal |
| Different sizes | MOT failure |
| Different speed ratings | Legal, but the axle is limited by the lower one, and it may breach the vehicle’s minimum requirement |
| Different load indexes | Legal only if both meet the vehicle’s minimum requirement |
| Run flat mixed with standard | Legal in itself, but usually against the manufacturer’s specification on run flat equipped cars |
| Winter mixed with summer | Legal, and a genuinely bad idea |
| Directional fitted against the arrow | Not a mixing issue but a fitting fault. Check it while you are looking |
| Different tyres across front and rear axles, each axle matched | Legal and common |
Checked against the DVSA MOT Inspection Manual and the Road Vehicles (Construction and Use) Regulations 1986, regulation 26 on mixing of tyres, on the review date shown above.
Why “same size” is not the whole story
This is where most drivers, and quite a few used car sellers, get caught out.
Two tyres can both read 205/55 R16 91V and still be meaningfully different tyres.
Decoding that sidewall (see TyreSafe’s full guide to tyre markings if you want every code explained):
| Marking | Meaning |
|---|---|
| 205 | Section width in millimetres |
| 55 | Aspect ratio, sidewall height as a percentage of width |
| R | Radial construction |
| 16 | Rim diameter in inches |
| 91 | Load index |
| V | Speed rating |
Now, the things that can differ even when the size matches exactly:
Load index. It must meet or exceed the vehicle’s requirement. A lower rated tyre is the one that fails first under load, and it does so with a full car in it.
Speed rating. The axle effectively behaves as its lowest rated tyre, and some vehicles specify a minimum rating.
Construction. Run flat sidewalls are far stiffer than standard ones. Mixing them changes how the axle behaves, and it is generally against the manufacturer’s specification on run flat equipped cars.
Seasonal type. A winter tyre and a summer tyre on the same axle have very different grip characteristics in exactly the conditions where it matters most.
That is not academic in Scotland. A driver can be on an untreated icy side street at eight in the morning and on wet tarmac by three in the afternoon.
Directional or asymmetric pattern. Look for the rotation arrow and the OUTSIDE marking while you are checking.
Why it matters even when it is legal
No scaremongering here, just the mechanics.
Braking. Different compounds and patterns generate different levels of grip. Uneven braking force across an axle affects stability as well as stopping distance.
Wet weather. Different tread designs clear water at different rates. One side of the axle can begin to aquaplane before the other does, which is an unpleasant surprise at speed.
Different tread depths. A deeper tyre and a shallower one on the same axle behave differently in the wet, even when both are perfectly legal.
Electronic systems. ABS, traction control and stability control are calibrated on the assumption that the wheels behave comparably. Mismatched grip makes their job harder and their intervention less predictable.
Pulling and uneven wear. A mismatched axle is one common cause of a pull appearing after tyre work. See why a car pulls to one side after new tyres.
AWD and 4×4. This is the genuinely serious case. Different rolling circumference across an axle can load the drivetrain continuously.
Check your handbook’s permitted variation, because the tolerances are small and vehicle specific. We covered this properly in what to do when a garage says you need four new tyres.
What about the MOT?
Clean and specific:
- Different sizes or different structures on the same axle: failure item
- Different brands or patterns: not a failure on its own
- Tread below 1.6mm across the central three quarters, around the full circumference: failure, regardless of matching
- Advisories may note mismatched tyres. That is advice, not a fail
Check the exact wording against the current inspection manual. If you have already failed, see what to do when your car fails the MOT on tyres, which covers the free retest rule most drivers never hear about — RAC Drive has a clear breakdown of the 10 working day window if you want the general rules.
What about insurance?
Fair and measured, because this topic attracts a lot of scare stories.
Insurers expect a vehicle to be roadworthy. The clear risk is an illegal tyre, not a legal but mismatched one.
Where a tyre’s load index or speed rating falls below what the vehicle requires, that is a specification issue and worth avoiding on its own merits.
This is general information rather than insurance advice, and policy wordings vary. Read yours if you are concerned.
How it happens, and how to fix it properly
The usual cause is entirely understandable. One puncture, one tyre replaced, and money was tight that month.
That was probably the right call at the time. Here is how to sort it out sensibly.
In priority order:
- If anything on the axle is illegal or unsafe, replace it now. No debate
- If it is a construction or size mismatch, correct it. That is a failure waiting to happen at your next MOT
- If it is a brand or pattern mismatch with similar tread depths, plan to match the axle at the next replacement. Do not bin good rubber today
That third point is worth saying plainly, given who is saying it. We sell tyres, and we are telling you not to buy any today. If your axle is legal and the depths are close, the right move is to match it when those tyres are due anyway.
When you do replace in pairs, remember new tyres go on the rear axle regardless of which axle drives the car. That may mean all four wheels come off, and TPMS positions and pressures change with them. See when your tyre pressure light stays on.
One practical habit: photograph all four sidewalls and keep them on your phone. It makes every future quote faster and stops anybody selling you the wrong size.
Buying a used car? Read the tyres
Mismatched tyres tell you something about the car well beyond the tyres themselves.
Four different brands often means single tyre replacement over several years. That is a car maintained reactively rather than planned.
Two premium at the front and two budget at the rear, or the reverse, tells its own story about how the last owner made decisions.
Uneven wear across one tyre points at alignment or suspension rather than the tyre. Worth a proper look.
Check the DOT codes. Old tyres with deep tread on a low mileage car is a common combination and a real cost coming your way. See old tyres with good tread.
Check the locking wheel nut key is present. It is the most commonly missing item in any British boot. See what to do when you cannot find it.
Then use it in the negotiation. A set of four tyres is a real, quantifiable cost and a completely legitimate thing to raise before agreeing a price.
A note from the van
Mismatched axles turn up most often on cars bought within the last few months.
Somebody buys privately, everything looks fine, and then an MOT advisory or a slow puncture brings the tyres into focus. That is usually the first time anybody has read all four sidewalls.
The conversation we have most often on those jobs is not “you need four tyres.” It is “these two are fine, this axle needs matching, and here is why.” People remember which of those two answers they were given. Read more about how our team approaches jobs like this on our About Us page.
FAQs
Is it illegal to have different tyres on the same axle? Not usually. Different brands, tread patterns and tread depths are legal. Mixing construction types, meaning radial with cross ply, is illegal, and different sizes on the same axle will fail an MOT.
Can I mix tyre brands on my car? Yes, it is legal. Matching brand and pattern across each axle is better practice because it gives more consistent braking and wet grip.
Will mismatched tyres fail an MOT? Only if the mismatch involves different sizes or different construction types on the same axle, or if a tyre is below 1.6mm. Different brands or patterns alone will not fail, though they may be noted as an advisory.
Can I have different tread patterns front and back? Yes. Different tyres across front and rear axles is legal and common, as long as each axle is matched.
Can I mix winter and summer tyres? It is legal but unwise, particularly on the same axle. The two have very different grip characteristics in the conditions where grip matters most.
Can I mix run flat and normal tyres? Legal in itself, but usually against the manufacturer’s specification on a vehicle designed around run flats. The sidewall stiffness differs substantially, which changes how the axle behaves.
Do different tyres affect insurance? Insurers expect a roadworthy vehicle. Illegal tyres are the clear risk. Legal but mismatched tyres are less so, though a load index or speed rating below the vehicle’s requirement is a specification issue worth avoiding. Check your own policy wording.
Does the speed rating have to match? The axle is effectively limited by its lowest rated tyre, and some vehicles specify a minimum rating. Matching ratings across an axle is the sensible approach.
Not sure whether what is on your car is legal?
Send a photo of each sidewall on WhatsApp and we will tell you what you have got, whether it passes, and whether it actually needs changing yet.
That last part is the useful bit. Sometimes the answer is no.
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