Guides
Puncture repair or replacement — can your tyre be saved?
A nail in the middle of the tread is usually fixable; damage in the sidewall never is. Here is how BS AU 159 — the British Standard every reputable repairer works to — decides which punctures can be repaired and which tyres must be replaced.
Last reviewed: September 2026 · LCDrive editorial team
The quick answer
Most punctures can be fixed. A nail or screw in the middle band of the tread, leaving a hole under 6mm across in a tyre that is otherwise sound, is usually a permanent repair for a fraction of the price of a new tyre. Damage in the sidewall or at the shoulder, a tyre that has been driven flat, or a tyre with cords showing means replacement — no reputable repairer will patch any of those.
The referee is BS AU 159 — in full, BS AU 159g:2013 — the British Standard for repairs to tyres used on the public highway. It defines where a tyre may be repaired, how large the damage may be, and the inspection every tyre must pass first. Reputable fitters work to it, including our own mobile puncture repair service, and the rest of this guide walks through what it actually says.
The repairable zone — area T
BS AU 159 confines minor repairs to a central band of tread it calls area T, and the width of that band scales with the tyre. It is set as a percentage of the nominal section width — the first number in the tyre size, so 205 in 205/55 R16: 60% of that width for tyres up to 155mm wide, 65% over 155mm and up to 200mm, and 70% above 200mm. In everyday terms, roughly the central three-quarters of the tread. Outside area T — the shoulder and the sidewall — repair is not an option at any price: a repair there may not preserve the structural integrity of the tyre, and the standard does not approve it.
Within area T there is a size limit too. The hole may be no more than 6mm across — about the diameter of a pencil — measured at the base of the injury after the hole has been cleaned out and prepared. That last part matters: a puncture that looks tiny from outside can measure over the limit once the damaged rubber around it is removed, so the deciding measurement is the one the fitter takes after preparation, not the thickness of the nail.
What rules a tyre out entirely
Before any repair, the standard requires the tyre to come off the wheel for a thorough inspection, inside and out — and it lists the findings that end a repair on the spot, however small and well-placed the puncture is.
| What the inspection finds | Why it ends the repair |
|---|---|
| Tread at or below the 1.6mm legal minimum | The tyre is at the end of its life anyway — the standard will not put a new repair into a worn-out casing |
| Damage in the sidewall or on the shoulder | Outside the repairable zone; a sidewall repair may not hold the structure of the tyre together and is not approved |
| Signs of running flat or badly under-inflated | Running deflated grinds the casing and inner liner apart from within — damage no repair can undo |
| Splits, cuts or cracking reaching the casing | The damage has gone past the rubber into the load-bearing skeleton of the tyre |
| Exposed cords, or tread, sidewall or belt separation | The layers of the tyre are already coming apart |
| Bead damage, including a broken bead core | The tyre can no longer be trusted to seal and stay seated on the wheel |
| A previous repair not made to the standard | An unknown repair underneath makes the whole casing suspect |
| Significant contamination — oil, solvent or sealant residue | Contaminated rubber will not bond, so a permanent repair cannot take |
Two rows deserve a closing note. The first: a tyre already at the legal minimum fails before the puncture is even examined — if yours is close, read the tread depth law guide and put the repair money toward the replacement instead. The second: aerosol sealants. They are get-you-moving measures, nothing more, and many repairers will refuse to attempt a permanent repair on a tyre that has had sealant in it, because the residue stops the repair bonding. Space-saver spares, finally, sit outside the standard altogether — a punctured temporary spare is replaced, not repaired.
Plug, patch or both — what a proper repair looks like
A repair to BS AU 159 always begins with the tyre coming off the wheel, because internal damage cannot be seen from outside — which is why a repair done with the tyre still mounted cannot comply, whatever it costs. Once the casing passes inspection, the repairer seals the injury from the inside in one of two approved ways: a one-piece rubber combination repair — the “mushroom” plug-patch, whose stem fills the hole while its cap bonds to the inner liner — or a separate rubber patch over the injury plus filling material through it. Either way the repair is bonded to the tyre from within and becomes part of it.
That rules out the two shortcuts you may have met. String plugs pushed in from outside a fitted tyre, and liquid sealants, sit explicitly outside the scope of the standard, and the British tyre industry trade body lists both as not acceptable. Neither involves looking inside the tyre, so neither can say what the nail did on its way in. They are not illegal — BS AU 159 is a standard, not legislation — but they are not recognised under the British Standard. A tyre plugged that way carries a previous repair outside the standard, which fails the pre-repair inspection next time it is in front of a professional; sealant residue is commonly treated the same way, as contamination. Work done properly is traceable, too: the standard says major repairs should be marked “BS AU 159” inside the casing along with the identification of the repairer.
Run-flats, speed ratings and other special cases
Run-flat tyres sit outside BS AU 159 altogether — the foreword of the standard says so in as many words — so there is no British Standard method for repairing one, and most fitters will not. Manufacturer policies vary from there: Pirelli says a punctured run-flat should be replaced rather than repaired, several other makers rule repairs out entirely, and a few allow a professional repair in narrow circumstances — check the guidance from your tyre maker and your car maker. A run-flat that has been driven while deflated is generally beyond saving in any case: the reinforced sidewall is stiff enough to hide internal damage that a conventional tyre would show plainly.
One persistent myth is that a repaired tyre must be downgraded — treated as slower-rated than it was. It must not: a tyre repaired to BS AU 159 keeps its original speed and load rating, which is the whole point of the inspection regime. Nor does the trade body’s published summary of the standard set any cap on the number of minor repairs, provided the repairs do not overlap — though in practice many fitters impose their own limits, commonly a single repair in the lifetime of a V-rated or faster tyre. Since it is their name inside your tyre, that is their call to make.
Repair or replace — the money question
A puncture repair is one of the cheapest jobs in the tyre trade. At a garage or fast-fit chain a repair typically runs £20 to £40 — one national chain advertises £30 including a new valve and a wheel balance — and mobile repair, where the work comes to you, typically costs somewhat more. A new tyre runs roughly £50 to £200 or beyond depending on size and brand, so where a repair is safe it wins on price by a distance.
There are times when a repair is false economy all the same. A tyre with tread already near 3mm is at the point where industry guidance says to plan its replacement — the repair money is better added to the new tyre. The same logic applies to a second or third puncture in a budget tyre.
There is a legal edge to the decision as well: driving on a defective tyre can reach a £2,500 fine and three penalty points per tyre, so a tyre that fails the inspection is not one to nurse along. If the answer is replacement, you can find the right sizes by registration or browse tyres by size.
Found a nail? Do this now
Leave the nail in. It is often part-sealing the hole it made, and pulling it out can turn a slow leak into a flat tyre in minutes. Check the pressure instead — with a gauge if you have one. If the tyre is holding air, drive gently and get it inspected soon; if it is losing pressure quickly, or the object is in the sidewall, stop — driving on can destroy a tyre that might have been saved.
Better still, stay where you are and let the workshop come to you. LCDrive operates 24/7, UK-wide, with emergency dispatch within 30 minutes when you need it now — call or WhatsApp 07904 781880. The tyre comes off the wheel, is inspected inside and out, and is repaired to BS AU 159 when a repair is safe — or replaced honestly, backed by the 6-month guarantee, when it is not.