Key takeaways
- A car tyre puncture can usually be repaired if the hole is no more than 6mm across after it is cleaned out, sits in the central repair area of the tread, and the tyre is sound when inspected from the inside.
- BS AU 159 is a British Standard, not an Act. The law for your own car sets the condition a tyre must be in; it does not say how a repair must be done.
- The repair area is 60 to 70% of the tyre's width depending on its size: about 144mm across the middle of a 205 tyre. Punctures in the shoulder or sidewall cannot be repaired.
- Plugs pushed in from outside, sealant and an inner tube in a tubeless tyre are not recognised as repairs under the standard. Treat them as temporary.
A punctured car tyre can usually be repaired when the hole is small, sits in the middle of the tread and the tyre is sound inside. It cannot be repaired when the puncture is in the shoulder or sidewall, the tyre has been damaged by being driven while flat, or the tread is worn to the 1.6mm legal minimum. Those cases mean a new tyre.
Those rules come from BS AU 159, the British Standard for tyre repairs, which every reputable fitter works to. It is not the same thing as the law, and it is not the same as a tyre maker's or a chain's own policy. Most of the confusion about whether a tyre "can" be repaired comes from mixing those three up. The sections below separate them, then take each repair rule in turn.
Is BS AU 159 the law?
No. BS AU 159 is a British Standard published by BSI. It sets out which damage can be repaired and how. The law for the car you drive is regulation 27 of the Road Vehicles (Construction and Use) Regulations 1986, and it covers the tyre's condition, not the repair method. For example, it allows no cut longer than 25mm or 10% of the section width, whichever is greater, that is deep enough to reach the cords. We found nothing in it about how a puncture must be repaired.
The one place UK law writes the standard in is the Motor Vehicle Tyres (Safety) Regulations 1994, which say a repaired part-worn tyre supplied for road use must meet BS AU 159. Those regulations still name the 1990 edition; trading standards guidance notes that the current edition is BS AU 159G.
| Layer | What it decides | Where it comes from |
|---|---|---|
| The law for your car | Whether the tyre is fit to use: no deep cuts to the cords, no bulges, no exposed cords, at least 1.6mm of tread | Regulation 27, Construction and Use Regulations 1986 |
| The law for part-worn tyres sold | A repaired part-worn tyre sold for road use must meet BS AU 159 | Tyres (Safety) Regulations 1994, regulation 7 |
| The British Standard | Where a repair can go, how big the hole can be, what rules a tyre out, how it is done | BS AU 159, summarised by the BTMA |
| Maker and fitter policy | Extra limits, such as no run-flat repairs or one repair per tyre | Each tyre maker and each fitter |
So when a fitter says a tyre "cannot legally be repaired", what they usually mean is that it falls outside the standard, or outside their own policy. Both are good reasons not to repair it. Neither is the same as the law.
The four repair rules in BS AU 159
A tyre has to pass all four of these, and the tyre maker's own policy, before a fitter can repair it.
Rule 1: where the hole is
A repair can only go in what the standard calls area T, a band across the middle of the tread. The British Tyre Manufacturers' Association's summary of BS AU 159 sets its width as a share of the tyre's nominal section width, which is the first number of the size on the sidewall (the 205 in 205/55 R16):
| Tyre width | Repair area (area T) | Example |
|---|---|---|
| Up to 155mm | Central 60% of the width | 155 tyre: 93mm |
| Over 155mm, up to 200mm | Central 65% | 195 tyre: 127mm |
| Over 200mm | Central 70% | 205 tyre: 144mm. 225 tyre: 158mm. 255 tyre: 179mm |
All widths in this table are from the BTMA's own calculated table.
Tread law measures three-quarters of the tread; area T is a share of the full section width. You will often read that repairs are allowed in "the central three-quarters", but that phrase comes from the tread depth law and the 1.6mm legal minimum. Check the figure for your tyre size rather than the shorthand.
A puncture anywhere outside area T, in the shoulder or on the sidewall, cannot be repaired as a minor repair. That part of the tyre flexes every time the wheel turns, and a patch there is working against the tyre the whole time. Any puncture through the sidewall, a cut deep enough to reach the cords, or a bulge rules the tyre out, as our guide to tyre sidewall damage explains.
Rule 2: the 6mm limit
In area T, the BTMA summary gives a maximum of 6mm for the diameter of the damage, measured at the base of the injury after the hole has been prepared. Two details matter:
- It is measured after cleaning out. The hole is reamed to take the repair, so a fitter cannot judge it properly from outside the tyre.
- Treat 6mm as the edge, not the target. Continental's repair guidance says a hole of 6mm or more is not repairable, so a hole right at 6mm may be refused.
An ordinary nail or screw is usually well inside the limit. A slash from glass or metal, a hole torn by a bolt, or a puncture made bigger by driving on the object usually is not. The BTMA summary sends larger damage in an otherwise sound tyre to an approved major repairer, not a roadside minor repair. In practice, fitters usually replace a car tyre rather than send it away for a major repair.
If you have just found a nail in the tread, our nail in tyre guide covers what to do. Leave it where it is: pulling it out lets the air go and makes the hole harder to assess.
Rule 3: more than one repair
The standard does not cap the number of repairs. The BTMA summary says there is no limit to the number of minor repairs in area T, provided the repair patches do not overlap. Two nails well apart in the middle of the tread can often both be repaired. A new hole close to an old repair usually cannot, because the new patch would sit on top of the old one.
Tyre makers can be stricter. Goodyear, for example, says its run-flat tyres may only have one repair in their lifetime. An earlier repair that was not done to the standard, such as an old plug pushed in from outside, also counts against the tyre. The exception is a specialist repair by the original tyre maker.
Rule 4: the inside has to be sound
This is the rule a driver cannot check, and the one that turns most "it is only a small nail" jobs into a new tyre. The standard requires the tyre to be removed from the wheel and inspected inside and out. The BTMA summary lists conditions that rule a repair out:
- Tread at the legal minimum of 1.6mm.
- Damage from running flat or badly under-inflated, or the inside torn up by the point of the object.
- Splits, cuts or cracking that reach the casing, or the casing breaking up.
- Bead damage, including a broken bead wire.
- The inner liner deteriorating.
- Cords showing through worn tread or a scuffed sidewall.
- The tread, sidewall rubber or belts separating.
- An earlier repair that was not done to the standard, unless it was a specialist repair by the original tyre maker.
- Heavy contamination from solvents or similar.
Running flat is the one that catches most people out. Nothing shows from outside. Fitters spot it on the inside as rubber dust, a crease or a scuffed band around the inner sidewall where it was pinched against the rim. The BTMA summary does not set a distance that is too far. What matters is whether the inside is damaged, and Kwik Fit's advice is not to drive on a flat tyre so that it has the best chance of being repairable. That is why we say not to drive on a flat tyre, even to a garage.
Does a repair lower the speed rating?
Not if it is done to the standard. The BTMA summary states that tyres repaired to BS AU 159 can operate at their original speed and load capabilities. A properly repaired tyre is not a downgrade, and you do not need to drive it differently.
Two honest limits. That statement comes from the BTMA's extract of the 1997 edition of the standard, and the current G edition may differ in detail. And for some high-performance and run-flat tyres, the maker's own guidance sits on top of the standard. Where a maker says a particular tyre should not be repaired, a fitter should follow that.
Run-flat tyres
Run-flats are the hardest case, for two reasons. They are built to keep going after losing pressure, and Kwik Fit points out that the added strength of a run-flat can mask damage from being driven on too far or too fast. And the makers do not agree on repairs. TyreSafe notes that several industry associations do not recommend repairing a run-flat.
Goodyear says its own run-flats can be repaired by a qualified professional after a thorough inspection and a check of the tyre's history, once only. Some large chains do not repair run-flats at all: Kwik Fit, for one, says it cannot carry out minor repairs on them. Our guide to whether a run-flat can be repaired covers how far you can drive on one and how to tell if you have them.
How long can you drive on a punctured run-flat? Only as far and as fast as the car and tyre maker allow, so follow the run-flat distance and speed limits in your handbook and keep the trip short. Goodyear lists a tyre driven at low or zero pressure for a substantial distance as one that cannot be repaired.
Plugs, sealant and tubes: are they legal, and are they repairs?
The BTMA summary lists these as not acceptable repair methods under BS AU 159:
- Plugs applied from outside to a tyre still on the wheel: string plugs and other plugs pushed in from outside, as sold in roadside kits.
- Liquid sealants.
- An inner tube fitted inside a tubeless tyre.
- Any temporary repair.
On whether a plug is legal: we have not found a UK law that makes driving a private car on a plugged tyre an offence in itself. So we will not tell you it is illegal. What is clear is that it is not a repair under the standard, nobody has looked inside the tyre, and the tyre still has to meet the condition rules in regulation 27. TyreSafe describes kits and sealant as temporary measures until you can get professional help. Our tyre repair kit guide covers using one safely. After any of them, have the tyre taken off and checked, and tell the fitter if you have used sealant.
Why one fitter says yes and another says no
Two fitters can look at the same nail and give different answers, and both can be right. The usual reasons:
- One looked inside and one did not. A quick look at the tread cannot show running-flat damage, the true size of the hole once cleaned out, or an old repair on the liner.
- The hole is on the edge of area T. On a 205 tyre the repair area is a 144mm band across the middle, so a screw in the outer tread blocks can sit just outside it.
- Policy is stricter than the standard. A chain that never repairs run-flats, or a maker that allows one repair per tyre, will refuse jobs the standard alone would allow.
- The tread is close to the limit. The standard rules out a tyre at 1.6mm. A tyre just above it is still repairable, but it will need replacing soon anyway, and a good fitter will say so.
It is fair to ask a fitter to show you why a tyre cannot be repaired. With the tyre off the wheel, the reason is usually something you can see.
What a proper repair involves
- The tyre is taken off the wheel. A repair to the standard cannot be done with the tyre still on the car.
- The tyre is inspected inside and out for the conditions listed above, and the object is found and removed.
- The injury is cleaned out and measured, and the inner liner around it is prepared.
- The repair is fitted from inside: either a one-piece rubber plug and patch, or a patch with a separate filler for the hole. The BTMA summary notes that a hole running through the tyre at more than 25 degrees may need the two-piece method.
- The tyre is refitted, inflated to the pressure on the car's placard and the wheel balanced.
Done this way, the repair is permanent. The tyre can then be used for the rest of its life, until it wears to the legal limit or something else damages it.
What to tell us when you call
Five details let us say on the phone whether it is likely to be a repair or a replacement, and bring the right tyre either way:
- Where the object is. Middle of the tread, near the edge, or on the side. A photo on WhatsApp is ideal.
- The tyre size from the sidewall, for example 205/55 R16 91V, plus any run-flat marking such as RFT, ROF, SSR or ZP.
- Whether it went flat and was driven on, and roughly how far.
- Whether you have the locking wheel nut key. If it is lost, say so, because we can remove a locking wheel nut without the key.
- Where the car is: driveway, car park or street, and whether there is room to work beside the wheel.
If the tyre has been going soft over days with nothing in the tread, the cause may be the valve or a corroded rim rather than a puncture. Our slow puncture guide covers those.
Getting the tyre inspected where it is parked
Whether a puncture can be repaired is only settled once the tyre is off the wheel. Our mobile puncture repair brings that inspection to the car: we check the damage against BS AU 159 and repair it if the standard allows. If it does not, we fit a new tyre where the car is parked the same day, or fit one you have already bought.
We work 24/7, typically reach you within 30 to 60 minutes across London and the surrounding counties, and fitting takes 20 to 30 minutes once we are there. There is no out-of-hours surcharge, and the price is quoted on the phone before anyone sets off. If the tyre is already flat and you need someone now, use our 24/7 emergency tyre call-out.
Tell us where the object is and the size on the sidewall. We inspect the tyre off the wheel, repair it if the standard allows, and fit a replacement the same day if it does not.
Sources
Checked on 2 October 2026. The full text of BS AU 159 is a paid BSI publication and was not read for this guide. The repair rules here come from the BTMA's licensed summary of the 1997 edition, last reviewed in 2014; the current edition is G and may differ in detail. The tyre maker and fitter pages are quoted as they stood on 2 October 2026, and their policies can change. What a fitter looks for inside the tyre is described as the job is done, not quoted from the standard.
- Minor repairs to passenger car and light van tyres (British Tyre Manufacturers' Association, PDF)
- Road Vehicles (Construction and Use) Regulations 1986, regulation 27 (legislation.gov.uk)
- Motor Vehicle Tyres (Safety) Regulations 1994, regulation 7 (legislation.gov.uk)
- Part-worn tyres: trading standards guidance (Isle of Anglesey County Council)
- The Highway Code, Annex 6: vehicle maintenance, safety and security (GOV.UK)
- The Highway Code, rules 274 to 287: breakdowns and incidents (GOV.UK)
- Driving on motorways (National Highways)
- The complete guide to punctures and repairs (TyreSafe)
- Can run flat tyres be repaired? (Goodyear)
- Tyre repair (Continental Tyres)
- Can my tyre be repaired? (Kwik Fit)
Photo: Gustavo Fring on Pexels
Frequently asked questions
We have not found a UK law that makes driving a private car on a string-plugged tyre an offence in itself. But the BTMA summary of BS AU 159 lists plugs applied from outside as not an acceptable repair method, and nobody has inspected the tyre inside. Treat a string plug as temporary and have the tyre taken off and checked.
Often, yes. If the nail is in the central repair area of the tread, the hole is no more than 6mm once cleaned out, and the tyre has not been damaged inside by running flat, it can be permanently repaired. Leave the nail in until a fitter removes it.
When the puncture is in the shoulder or sidewall, the hole is over 6mm once cleaned out, the inside shows damage from running flat, the tread is at the 1.6mm legal minimum, a new patch would overlap an old repair, or there is bead damage, exposed cords or separation. Some makers also rule out repairs on certain tyres.
No. The sidewall is outside the BS AU 159 repair area. It flexes constantly, which is why a patch there would not hold, so a puncture through the sidewall, a cut deep enough to reach the cords, or a bulge means a new tyre.
Yes, under BS AU 159. The BTMA summary says there is no limit to the number of repairs in the central repair area, as long as the patches do not overlap. Some makers are stricter: Goodyear allows one repair in the lifetime of its run-flat tyres.
A repair done to BS AU 159 is permanent. The BTMA summary says a repaired tyre keeps its original speed and load capability, so you can use it until it wears to the legal limit or is damaged again. A plug or sealant from a kit is different: that is temporary until the tyre is inspected.
Yes, if the tyre is repairable. The BTMA summary says a tyre repaired to BS AU 159 keeps its original speed and load capability, so a proper repair puts it back to full use for the rest of its tread life. If the tyre fails any of the repair rules, a new tyre is the only safe answer.
Usually because the hole is outside the central repair area, it is too big once cleaned out, the inside is damaged from running flat, or the tread is at the limit. A shop may also have its own policy, such as not repairing run-flats, which can be stricter than the standard.
It depends first on whether the tyre can be repaired, which needs it off the wheel. We quote on the phone before anyone sets off, and there is no out-of-hours surcharge for nights, weekends or bank holidays.