Got a puncture? What to do next
A lot of drivers only find out at the side of the road that their car hasn't got a spare. Many newer cars come with a sealant kit instead, or with run-flat tyres. Here's what to do, in order, and what that sealant actually does to your tyre.
1. Get somewhere safe
- Hazard lights on, slow down gently and pull off the road as far as you can, ideally somewhere level.
- Don't drive far on it. A few hundred yards to a safe spot is fine; miles on a flat tyre will wreck the tyre and can damage the wheel.
- On a motorway, leave at the next exit if you can, or stop in an emergency area or on the hard shoulder. The Highway Code says not to attempt repairs on the motorway: get out on the side away from traffic, get behind the barrier if it's safe, and call your breakdown service.
- If you're stuck in a live lane, stay in the car with your seatbelt on and hazards on, and call 999.
2. See what you've got
Lift the boot floor. You'll find one of these:
- A full-size spare. Change the wheel, then get the punctured tyre looked at.
- A space-saver spare. A thin temporary wheel with a speed limit, usually 50 mph, printed on it. Use it to get to a tyre fitter, not for the rest of the week.
- A sealant kit: a bottle of sealant and a small compressor that plugs into the car.
- Nothing at all, which usually means run-flat tyres. Check the handbook for how far and how fast you can go.
Don't forget the locking wheel nut key if your wheels have them. It's usually in the glovebox or with the jack.
3. Using a sealant kit or can
Sealant works on a small hole in the tread, like a nail or a screw. It won't fix a cut or bulge in the sidewall, a big gash, or a tyre that's come off the rim.
- Follow the instructions on the kit. Usually you inject the sealant through the valve, pump the tyre up, drive a short way gently to spread it round, then stop and check the pressure again.
- Stick to the limits. Kits give a maximum speed and distance, often on a sticker to put on the dashboard. It's a get-you-home fix, not a repair.
- If you can see a nail, leave it in. Pulling it out makes the hole bigger.
Does puncture foam ruin the tyre?
Not necessarily, and it's a common worry. If the hole is in a repairable place, a tyre that's had sealant in it can often still be properly repaired, as long as the sealant is cleaned out. Water-based sealants wash out easily and don't leave lasting damage. A few things to know:
- Get it seen within a day or two. The longer sealant sits in the tyre, the harder it is to clean out.
- Tell the fitter you've used sealant before they take the tyre off. Some charge a small fee to clean it out, and some types of sealant are harder to remove than others.
- Sealant can clog a tyre pressure sensor. On cars with sensors in the wheels, ask the fitter to clean or check it. Car makers recommend using only the sealant they approve for this reason.
Can the puncture be properly repaired?
Tyre repairs in the UK follow a British Standard, BS AU 159. A car tyre can usually be repaired if:
- The hole is in the central three-quarters of the tread. Too near the edge or in the sidewall, and it can't be.
- It's no bigger than 6mm across.
- The tyre hasn't been damaged by driving on it flat. The fitter takes the tyre off and checks the inside.
A proper repair is done from inside the tyre with the tyre off the wheel. A plug pushed in from outside isn't a permanent repair. Most fitters won't repair a run-flat tyre, so expect to replace it.
Worth keeping in the boot
A hi-vis vest, a torch, a pair of gloves, the locking wheel nut key, a phone charger, and your breakdown cover number. And check the spare's pressure now and then: a flat spare is no help.