Tubeless puncture kit: what is inside and how to use it

A tubeless puncture kit is a pocket-sized set of tools for plugging a nail or screw hole in the tread of a tubeless tyre while the wheel is still on the car. A typical kit holds a pair of pliers, a spiral probe (often called a reamer), an insertion needle with a handle, a tube of rubber cement, a bundle of sticky rubber strings and a small blade. You pull the object out, open and clean the hole with the probe, push a cement-coated string into it with the needle, trim the ends and pump the tyre back up, and you can drive on. What it does not do is make the tyre as good as new. Tyre makers treat a plug pushed in from outside as a temporary fix, because nobody has looked inside the tyre to check for hidden damage. Plan on a proper workshop repair within a day or two.

What a tubeless puncture kit contains

The contents vary a little by brand, but CEAT’s description of a do-it-yourself kit is a good checklist of what you should find in the box:

• Pliers, for gripping and pulling out the nail, screw or stone.
• A spiral probe, a T-handled rasp that you screw into the hole to clean it and widen it to the size of the plug.
• An insertion needle, a T-handled tool with an open eye at the tip that carries the string into the tyre.
• Rubber cement, which lubricates the probe and helps the string bond to the hole.
• Repair strings, the strips of sticky, spongy rubber that do the actual sealing. One string per hole is the norm, so a kit with several lets you deal with more than one puncture.
• A blade, for trimming the string flush with the tread.

Better kits add a pressure gauge, valve cores and a small compressor that runs off the car’s 12-volt socket. The compressor matters more than it looks: a plugged tyre is useless if you have no way to put air back into it, and many punctures happen far from a pump.

String plug kits and sealant kits are different things

Two kinds of product are sold as “tubeless puncture kits” in India, and they work in opposite ways.

A string plug kit, described above, fills the hole mechanically from the outside. It works on tubeless tyres only, because a tube-type tyre loses its air through the tube, not through the casing.

A sealant kit is a bottle of liquid sealant and a compressor. You pump the liquid in through the valve, and the escaping air carries it into the hole, where it sets. Since July 2020, the Central Motor Vehicles Rules allow passenger cars that run tubeless tyres and have a tyre pressure monitoring system to carry a repair kit of this kind instead of a spare wheel. Sealant kits are quicker and need no tools, but the liquid has to be cleaned out before a proper repair. Our tyre sealant guide covers them in detail.

How to plug a tubeless tyre, step by step

Stop somewhere flat and safe, away from traffic, switch on the hazard lights, turn the engine off and pull the parking brake. Then:

1. Find the hole. Often the nail or screw is still in the tread. If you cannot see one, roll the car forward half a turn and look again, or listen for the hiss.
2. Pull the object out with the pliers. The tyre will start losing air faster, so work steadily.
3. Ream the hole. Coat the spiral probe with a little cement, push it into the hole and twist it in and out several times. This cleans the hole and roughens its sides so the string can grip.
4. Load the needle. Thread one string through the eye of the insertion tool until equal lengths hang on each side.
5. Insert the string. Pull out the probe and push the loaded needle straight into the hole until only a short stub of string shows on each side.
6. Withdraw the needle without twisting it. CEAT’s instruction is to pull the tool straight out; twisting it can pull the string out with it.
7. Trim the ends close to the tread with the blade.
8. Reinflate to the pressure on the door placard or in the handbook, then check the plug for bubbles with a little water. Our pressure lookup has the figures for common Indian cars.

If the tyre still leaks, a second string next to the first sometimes helps. If it still leaks after that, the hole is too large or in the wrong place for a kit.

When a plug is not enough

A string plug can only seal a small, round hole in the tread. The industry repair procedures published by the U.S. Tire Manufacturers Association set out the limits clearly:

• The injury must be no larger than 6 mm across.
• It must be in the tread area, not in the shoulder or at the edge of the steel belts.
• A hole that runs at an angle into the shoulder is not repairable.
• Repairs must not overlap, and a tyre with an earlier improper repair should be scrapped.

Michelin’s guidance for car owners in India adds that punctures in the shoulder cannot be repaired and those in the sidewall generally cannot either. Any tyre that has been driven while flat or very soft may have damage inside that a plug will hide: the sidewall flexes far beyond its design and the inner rubber can be crushed or torn.

In practice, keep your kit in the boot for nails and screws in the middle of the tread. For a cut, a tear, a hole near the edge or a tyre that went fully flat on the move, fit the spare or call for help.

After the roadside fix

Treat a plugged tyre as a way to reach a tyre shop, not as the end of the job. Michelin does not recommend kit repairs as permanent because the inside of the tyre has not been inspected. CEAT says the same about its own kits: they give temporary support until the tyre can be examined.

The repair that tyre makers accept as permanent is made from inside. The USTMA procedure is explicit that the tyre must be taken off the wheel for inspection, and that a plug on its own or a patch on its own is not an acceptable repair: the hole is filled with a rubber stem and the inner liner is sealed with a patch, usually as one combined unit. Because of its shape, this is often called a mushroom repair. It costs more than a string, but it is the version that lasts. Our guide to tyre puncture repair explains the methods side by side.

Until you reach the shop, drive gently, keep the speed down, and check the pressure again after a few kilometres. A plug that is weeping shows up as a slow, steady drop.

Buying and keeping a kit

• Check what is in the box. A kit without a probe, or with only one or two strings, will not get you far.
• Look at the handles. The probe and needle take real force to push into a car tyre, so choose tools you can grip firmly.
• Check the cement every few months. An opened tube that has dried out leaves you reaming the hole dry.
• Practise once on an old tyre at a shop if you can. The first time you use a kit should not be at night on a highway shoulder.
• Keep it with the jack, and keep a compressor or at least a foot pump with it.

A kit is not a substitute for a spare wheel if your car has one. It is a good addition to it: plugging a nail hole is often faster and safer than jacking up a car on a narrow roadside.