What are run-flat tyres?

They'll leave you deflated - but not stranded. How run-flat tyres work

BuyaCar team
Mar 7, 2017

Run-flat tyres do what they say: continue to operate when they are punctured.

The technology means that you don’t have to stop at the side of the road when your tyre is flat, but can continue your journey and get it replaced at a more convenient time.

It can also help you keep your car under control if the tyre has a blowout and suddenly deflates. Run-flat tyres are also more likely to hold together in one piece.

However, you do have to make some compromises. The most common type of run-flat tyres are heavier and more expensive than conventional ones. They are generally not as good at absorbing bumps in the road, although they are improving in this respect. And if you do have a puncture, you can only drive at a reduced speed, over a limited distance.

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How do run-flat tyres work?

Conventional tyres only work when they are pumped up. They require a cushion of air to inflate and to keep their shape. So if they suffer a puncture and the air leaks out, they go flat. Trying to drive on could mean the tyre becoming detached from the wheel or shredded.

But most run-flat tyres don’t just rely on air to keep their shape. They have thicker sides that are reinforced. These tyres still deflate if they get a puncture, but not completely. The strong sides maintain enough of their shape that they can still grip the road. These are also known as self-supporting run-flat tyres.

There’s another, less common type of run-flat tyre that’s made with a sticky sealant layer inside. After a small puncture, the sealant oozes in to plug the gap and prevent the tyre from completely deflating. These tyres don’t affect the ride comfort of the car in the same way as self-supporting ones do, but neither do they offer the same level of security: the system only works if the puncture hole is 5mm in diameter or less. Continental Tyres says that this accounts for 80% of all punctures.


Can I drive on a flat tyre?

Many tyre companies, including Continental and Pirelli, advise driving at a maximum of 50mph for a distance of 50 miles on a self-supporting run-flat tyre. This is because you damage these tyres when you drive them and they aren’t inflated. Travel too fast or too far and they can start to break up.

You’ll need to find a tyre workshop quickly, which could leave you in the lurch late on a Saturday evening in the rain.

Few tyre fitters will contemplate repairing a self-supporting run-flat tyre because of the damage that may have been caused when driving deflated, so you’ll almost certainly have to buy a replacement.

Self-seal tyres don’t have the same restrictions, but you’re advised to get the tyre examined soon after a puncture to ensure that it’s safe and allow it to be repaired if possible.


Run-flat tyres: the good

✔ Good chance of continuing your journey immediately after a puncture
✔ More control after a sudden deflation (blow-out)
✔ No need for a spare tyre or tyre repair kit


Self-supporting run-flat tyres: the not-so-good

✘ Expensive and can’t be repaired
✘ Can result in a bumpier ride
✘ Limited speed and range after a puncture

Self-seal run-flat tyres: the not-so good

✘ Only work when puncture hole is 5mm wide or less
✘ You need to have the tyre examined after a puncture
✘ Expensive


How do I know when a run-flat tyre has had a puncture?


Cars with run-flat tyres have a tyre pressure warning system that alerts the driver if low pressure is detected, which could indicate a puncture

Every car with these tyres has a pressure sensor that should alert you, with a light on the dashboard, if air escapes from the tyre - even if it’s only a small amount from a self-sealing one. Without these sensors, you may not notice.

However, these systems regularly isue false alarms. Driving too quickly over a pothole can squeeze the tyre and activate a low pressure warning.


How can I tell if my car has run-flat tyres

Some tyres clearly state "run-flat" on their side. The letters RFL make it easy to identify many others. However, some acronyms are a little less obvious.

  • RSC This is used on tyres that are made for BMWs and stands for Run Flat System Component
  • ROF Goodyear uses these letters to indicate a Run on Flat tyre
  • ZP Standing for Zero Pressure, this is Michelin's label for run-flat tyres
  • SSR Continental use the term Self-Supporting run-flat
  • DSST These letters stand for Dunlop Self Supporting Technology
  • DriveGuard This is Bridgestone's run-flat branding


Do cars fitted with run-flat tyres come with a spare tyre?

Part of the point of a run-flat is to avoid having to carry a spare tyre. You’ll find that where they are fitted as standard equipment, not only is there no spare tyre but there are no wheel-changing tools such as a brace and jack, either. As a side-benefit, the resulting weight reduction improves the car’s fuel economy.


How long do run-flat tyres last?

Since they’re built from the same materials as normal tyres, run-flat tyres should last as long as standard tyres.


Can I fit ordinary tyres to a car with run-flats?

Yes. But ff your car has been designed to run on stiffer self-supporting run-flat tyres, then it may not steer with the same precision on softer, conventional tyres. You’ll probably also want a backup in case of a puncture. This could be a tyre repair kit or a spare tyre, which will probably take up boot space.


Can I mix run-flat tyres with normal tyres?

You shouldn't because self-supporting run-flat tyres affect a car’s steering response and its bump absorption in a different way to conventional ones.

Also, you’ll be stuck if one of the conventional tyres has a puncture, unless you have a spare or repair kit.



Can I fit run-flat tyres to my car if it hasn’t had them before?

You can but it’s not advisable. You’ll notice the car’s ride and steering response changes because self-supporting run-flats are much stiffer. To improve things, you may need to change the car’s suspension settings.

However, more crucially, a car fitted with run-flat tyres must have a tyre pressure monitoring system so you know the tyre has been punctured and is losing air. If your car hasn’t got one of these, then fitting these tyres is a risk.


Which cars are fitted with run-flat tyres?

Tyre pressure monitors were made mandatory on new cars in 2012. Since then, manufacturers have increasingly been fitting runflat tyres to their vehicles.

You’ll need to check whether a particular car has them, because many manufacturers fit them on some cars and not on others.

Companies that use self-supporting run-flat tyres include Mini, BMW and Audi.

Volkswagen offers self-sealing run-flat tyres on its CC and Sharan cars.


How much do run-flat tyres cost?

Run-flat tyres are around twice as expensive as conventional tyres but the mandatory fitment since 2014 of tyre pressure sensors on new cars means more vehicles are being fitted with them, helping to drive down prices. As always, shop around.



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