Car Tyre repairs and sealants

How to fix a puncture with a tyre repair kit

Step-by-step guide to repairing a flat

Punctured tyre

Got a puncture? We’re always on hand to get you going again. But if you’d like to try fixing it yourself, we’ve got some simple tips for repairing a tyre.

If you’ve got a new-ish car, it might have a puncture repair kit instead of a spare tyre to change. A repair kit uses tyre sealant and a compressor to repair the hole in the tyre.

Here’s how to safely make a temporary repair so you can drive yourself to a garage.

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Before you start

  • Don’t try to fix a tyre on a motorway hard shoulder or at the side of the road.
  • Turn off the road or pull over in a safe place away from traffic.
  • Tell passengers to get out of the car and wait away from the vehicle and road.
  • Read the instructions on the repair kit before you start. If it’s different to our advice, always follow the instructions.

Step 1 - Get your car ready

Before you try to use the repair kit, make sure you and your passengers are in a safe place and the car’s prepared:

  • Switch off your engine.
  • Turn on your hazard lights.
  • Put the handbrake on, or
  • Put the vehicle into 'P' if you’re driving an automatic.
  • Make sure all passengers are out of the car and in a safe place.
  • Get the repair kit out (usually found in the boot).

The puncture repair kit should include a can of sealant and a compressor. It may also include warning stickers to place on the wheel and inside the car, to remind you to replace the tyre.

Step 2 - Find the puncture

You’ll need to look at the tyre carefully to find the puncture and check if it’s suitable for a repair.

Don’t use the repair kit if:

  • The puncture is more than 4mm in diameter.
  • The wheel rim is damaged.
  • The tyre has been flat or low pressure for an extended period.
  • The puncture is outside of the main tread area.

If you spot something like a nail or piece of glass that’s pierced the tyre, don’t try to take it out. That could make the hole bigger.

Step 3 - Position the wheel

Once you’ve found the puncture, you can re-position the wheel by driving forward a little to make it easier to repair.

  • Make sure the puncture is at the top of the tyre.
  • Try to position the air valve in the top half of the tyre.

If you’ve moved your car, remember to put the handbrake or parking brake back on.

Step 4 - Connect the sealant and compressor

Your puncture repair kit will include a bottle of sealant and a compressor. 

  • You’ll usually need to insert the sealant into the tyre through the air valve. The kit will explain how to do this.
  • You may need to remove the valve first and/or manually squeeze in the sealant.
  • You’ll then need to connect the compressor. This may connect to the tyre valve directly or to the bottle of sealant to help pump the sealant in. 
  • Plug the compressor into your car’s 12v socket or cigarette lighter.

Step 5 - Inflate the tyre

You’ll need to use the compressor to re-inflate your tyre. It may also pump the sealant into the tyre at the same time.

  • Check your vehicle manual to find the right tyre pressure for your vehicle.
  • Make sure your car is in neutral with the handbrake or parking brake on.
  • Turn on the engine and switch on the compressor.
  • The compressor will have a valve to show you the pressure level and may have a button to check the pressure.
  • Turn the compressor off and detach it once the tyre is at the right pressure.

Step 6 - Drive and re-check the tyre

Many sealant kits need you to drive a little way for the sealant to spread around the tyre. The kit will explain if you need to do this.

  • Drive as far as the repair kit recommends to spread the sealant.
  • Stop in a safe place and put the handbrake or parking break back on.
  • Check the tyre. 
  • If it looks damaged, you’ll need to call us out to help you.
  • If the sealant has worked, you can drive to a garage. You may need to inflate the tyre a bit more first, so check the instructions on the kit and the pressure in your handbook.

Step 7 - Replace the tyre

Once you’re satisfied that you’ve repaired the tyre using the kit, drive your car to the nearest garage or tyre fitters to replace the tyre. A tyre that's been repaired with sealant will almost always need replacing, however small the puncture was.

There's likely to be a restriction on how fast and how far you can drive on the repaired tyre. This should be in the instructions but if in doubt, stick to a maximum of 50mph for 50 miles. Make sure you drive carefully, especially when cornering and braking.

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Is a puncture repair permanent?

If you repaired a punctured tyre using a repair kit, it'll only be a temporary fix. You still need to take your car to a garage or tyre fitters as soon as possible.

That’s because the tyre has to be removed from the wheel to check for internal damage. If it has internal damage that’s not spotted, the tyre could fail later on, which could be very dangerous.

Any external plugs or liquid sealants injected through the tyre valve can’t be thought of as permanent repairs.

What are pre-puncture sealants?

A puncture repair kit is designed to be used post-puncture - it can temporarily repair a hole after your tyre’s been punctured.

But some sealant kits are designed to be pre-puncture. That means they’re inserted into an undamaged tyre and aim to stop your tyre going flat if you get a puncture in the future.

Are there risks with pre-puncture sealants?

The risk with pre-puncture sealants is that you may not notice if you ever do get a puncture. They’re designed to work almost instantly, so you might not realise that the sealant has been activated.

A large screw or nail ‘sealed’ into the tread could cause more damage over time and could even lead to a blowout.

If you’ve used a pre-puncture sealant, check your tyres every time you drive the vehicle. If the sealant’s been activated, you should see signs of the sealant (usually a white rubber-like substance) on the outside of the tyre.

Published: 16 December 2016 | Updated: 3 June 2020 | Author: The AA

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