Repair when the damage is minor and central; replace when it isn't. A small puncture in the middle of the tread on a healthy tyre is usually a safe, cheap repair. Sidewall damage, large holes, perished rubber, low tread or a tyre that's been driven flat all point to replacement. The deciding factor is always safety, not cost, and a proper inspection is what settles it.
Here's the simple way to tell which camp your tyre falls into, what the repair standard actually requires, and how the cost stacks up.
Repair if…
A tyre is usually repairable when all of the following are true, which is why a fitter checks each one:
- The puncture is in the central tread (the minor repair area defined by the British Standard).
- The hole is 6mm or smaller, with no other damage.
- The tyre has plenty of tread and isn't aged out.
- It wasn't driven on while flat, which would damage the casing.
Replace if…
Replacement is the only safe option when the damage falls outside that repair zone or the tyre is past its best:
- There's sidewall or shoulder damage, a bulge or a cut.
- The tread is near the legal limit anyway.
- The rubber is cracked or perished, or the tyre is older than its maker recommends (many advise a yearly check from five years and replacement by ten).
- It's a run-flat that's been driven while deflated.
The repair standard explained
Reputable repairers follow the British Standard BS AU 159, which is the same approach TyreSafe promotes for safe, lasting repairs. The key part most drivers don't realise is that a proper repair can only be judged after the tyre is taken off the wheel and inspected from the inside. That's because a puncture that looks fine from outside can have damaged the inner liner, especially if the tyre ran low. A plug pushed in from outside without that inspection isn't a standard repair, it's a temporary measure, which is why a fitter's internal check is the deciding factor.
The cost angle
A repair is far cheaper than a new tyre, so it's always worth checking whether a repair is possible first. But a marginal repair on a worn or old tyre is false economy, you'll be buying a tyre soon anyway, and the repair won't restore lost safety. The sensible rule is: repair if the tyre has plenty of life left and the damage is in the safe zone; replace if it's worn, old or damaged outside that zone. Compare typical repair costs against new tyre prices before deciding.
Repair zones at a glance
Where the damage sits on the tyre decides more than what caused it: the central three-quarters of the tread is repairable, the shoulders and sidewalls are not. This table covers the common cases.
| Damage | Where | Verdict |
|---|---|---|
| Nail or screw, hole up to 6mm | Central tread | Repair, after internal inspection |
| Hole larger than 6mm, or a tear | Central tread | Replace |
| Any puncture | Shoulder (where tread curves into sidewall) | Replace |
| Cut, bulge or puncture | Sidewall | Replace |
| Two punctures very close together | Central tread | Usually replace; the standard limits how close repairs can be |
| Puncture on a tyre driven while flat | Anywhere | Replace if the inner liner shows creasing or rubber dust |
| Slow leak with no puncture | Valve or wheel rim | Not a tyre repair: new valve or a cleaned and sealed bead |
The "central three-quarters" is measured across the tread width, so the zone is narrower than the size on the sidewall suggests: the 225 in 225/45 R17 is the full section width, and the tread is narrower than that. The shoulders flex more than any other part of the tyre, which is why a patch there will not hold and the standard rules it out. Repairs must not overlap, and some tyre makers restrict repairs on high speed-rated and run-flat ranges, so the fitter checks the maker's policy before repairing a performance tyre. A leak at the valve or bead is a different job entirely.
What a proper repair involves
A repair to the British Standard is done from the inside with the tyre off the wheel, and it takes a fitter with the right kit around half an hour. The steps are what separate a lasting repair from a plug that fails in the rain a month later:
- Deflate the tyre, break the bead and remove it from the wheel.
- Inspect the whole inner liner for creasing, rubber dust or damage that means the tyre was run flat. If it was, the repair stops here.
- Mark the injury and check its position and size against the repair limits.
- Ream or drill the injury channel clean, then buff the liner around it.
- Apply vulcanising cement and fit a combination plug-patch (often called a mushroom) from the inside, so the stem seals the channel and the patch seals the liner.
- Seal the edges, refit the tyre, inflate to the correct pressure and check for leaks.
- Rebalance the wheel, because the repair adds a small amount of weight.
A string plug pushed in from outside skips the inspection and the internal seal. It can hold air for a while, which is why it is sold as a get-you-home measure, but it is not a standard repair and should be replaced with one, see what to do about a nail in a tyre. TyreSafe publishes clear guidance on why the internal inspection is the non-negotiable part.
Sealant, run-flats and foam-lined tyres
Three tyre types change the repair answer: sealant makes a repair harder, run-flats are usually replaced, and foam-lined tyres can be repaired with extra work.
Sealant. The liquid from an emergency kit coats the inside of the tyre and has to be cleaned off before a patch will bond. Some fitters will do that; some will not, and some sealants are effectively permanent. If the car is parked somewhere safe, calling a fitter before using the kit keeps the repair option open.
Run-flats. A run-flat that has been driven on with no air has almost always damaged its reinforced sidewalls internally, and several manufacturers do not approve repairs on their run-flat ranges at all. Treat a run-flat puncture as a replacement unless the fitter can confirm the tyre was never driven deflated.
Foam-lined tyres. The sound-absorbing foam has to be cut back around the injury before the liner can be buffed and patched, after which the repair is standard. Tell the fitter in advance so they bring what they need.
If it's a replacement: one tyre or two?
Replacing one tyre is fine when the other tyre on the same axle has plenty of tread and is the same make and pattern; otherwise replace the pair. Grip should be balanced across an axle, especially in the wet, and a new tyre next to a half-worn one of a different design can make the car feel unsettled under braking.
Two further rules of thumb: many manufacturers recommend putting the newest tyres on the rear axle, because rear grip is what keeps the car stable if it aquaplanes, and on four-wheel-drive cars a large difference in tread depth between tyres can strain the transmission, so check the handbook before replacing a single tyre. Our guide to replacing tyres in pairs walks through the decision. Whatever you fit must be the correct size, with at least the load index and speed rating the car maker specifies; the handbook or tyre placard shows them.
Let us assess it
We'll give you a straight answer. We inspect the tyre where the car is, in London and the Home Counties and further out when the diary allows, and only recommend replacement when it's genuinely needed; otherwise we repair it on the spot.
