What are run-flat tyres?

Car makers use run-flat tyres to save carrying the weight of a spare wheel to save fuel and emissions.

When your car has had a puncture with a run-flat tyre, it’s unlikely it can be repaired. This is because the structure and safety of the tyre can be compromised when it’s been driven on while deflated. Thankfully, most drivers experience a puncture with their car once in every 50,000 miles of driving, so you shouldn’t need to rely on a run-flat tyre’s unique ability very often.

How do run-flat tyres work?

The key difference between a standard tyre and run-flat is the strength of the sidewall. This is the section of the tyre you see between the road and the wheel. With run-flats, it’s reinforced so it can support the weight of the car even when a puncture has caused all of the air to escape from inside the tyre. This is known as a self-supporting tyre.

There are also run-flat tyres that are self-sealing and have a special lining inside the tyre that ‘heals’ over punctures. The third type of run-flat is an auxiliary supported tyre with an internal structure. These are only used on military vehicles and armoured limousines in case the tyres are punctured by bullets, so you shouldn’t need them for a trip to the supermarket.

You might not notice any difference in the way the car drives even with a punctured run-flat tyre. However, the car’s TPMS (tyre pressure monitoring system) will flash up an alert on the dashboard to tell you one of the tyres is at a different pressure to the others. Some systems will tell you which tyre is deflated and others just that there’s a puncture. Either way, you should slow down and head for a garage to have a replacement tyre fitted. Most run-flat tyres can be driven on for up to 50 miles after they have punctured.