Not all tyre repairs are equal. There are three methods in common use, and only one of them is recognised as a permanent, compliant repair in the UK. Knowing the difference makes it easy to tell a proper repair from a temporary bodge.
The three methods
- Patch: a rubber patch bonded to the inside of the tyre. It seals the inner liner over the injury but does not fill the hole through the tread.
- Plug: a rubber or leather plug pushed into the hole itself, filling the puncture channel. On its own it does not seal the inner liner.
- Combination plug-and-patch: both together, applied from inside the demounted tyre. The plug fills the channel and the patch seals the liner.
Why combination is the proper repair
Each of the first two leaves a weakness. A patch alone seals the inside but leaves the puncture channel open, letting water and road dirt reach the steel belts and cords, where it can cause corrosion. A plug alone, especially one pushed in from outside without removing the tyre, cannot be relied on to seal the liner properly.
The combination repair does both jobs: it fills the hole and seals the liner, applied from inside the tyre after a full internal inspection. This is the only method recognised under British Standard BS AU 159 as a permanent repair, which is why a proper repair always involves taking the tyre off the wheel.
Emergency fixes are not repairs
Several products are sold for roadside use, and they have their place, but only as a way to reach a garage:
- External string or "gun" plugs inserted without removing the tyre
- Sealant foam or tyre-weld cans
- Patches applied from the outside
None of these is a compliant permanent repair. After using one, the tyre should be taken to a fitting centre for a proper inspection and either a correct repair or replacement; some online tyre shops, Tyres.co.uk among them, will even send a fitter to your door to do it. Sealant foam in particular coats the inside of the tyre and has to be cleaned out before any repair, so it is worth telling the fitter it has been used.
The foam-lined tyre myth
Some modern tyres have a layer of acoustic foam inside to cut road noise. There is a common belief that these cannot be repaired, but that is not so: the foam is extra work to peel back and replace around the repair, not a barrier to it. A foam-lined tyre with a repairable puncture can usually still be fixed.
From the workshop: I see plenty of tyres come in with an external plug already in them. It got the driver here, which is the point, but it is not the repair. The tyre comes off, gets inspected inside, and gets a proper combination unit, or it gets replaced. There is no halfway.
Sources and accuracy. The description of repair methods and their compliance here reflects the British Standard and industry guidance at the time of writing, which can change. Anything safety-critical should be confirmed against the current standard and a qualified fitter. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What is the difference between a plug and a patch?+
A plug fills the puncture hole through the tread, while a patch bonds to the inside of the tyre to seal the liner. A plug alone leaves the liner unsealed; a patch alone leaves the hole channel open. The combination does both.
Which tyre repair is the proper one?+
The combination plug-and-patch, applied from inside the tyre after it is removed from the wheel. It both fills the hole and seals the inner liner, and it is the only method recognised as a permanent repair under British Standard BS AU 159.
Are external plug kits or tyre foam any good?+
Only as an emergency. A string plug pushed in from outside, or a can of sealant foam, can get a car to a garage, but neither is a compliant permanent repair. The tyre still needs proper inspection and repair, or replacement.
Can a foam-lined or 'quiet' tyre be repaired?+
Usually yes. The acoustic foam inside some tyres is extra work to remove and replace around the repair, but it does not by itself prevent a proper repair. A fitter who says a foam-lined tyre can't be repaired is worth a second opinion.