Run flat tyres: what they are and how to identify them

A run-flat tyre is designed to allow you to continue driving (slowly and for a short distance) even after suffering a puncture. This is due to the reinforced sidewalls on the tyre, that bear the weight of the vehicle for a short amount of time.

This design aims to allow drivers to continue using a punctured vehicle in order to reach a garage, their home or another suitable location. It also helps the car cope with the initial impact of the puncture, thus helping you avoid losing control and crashing.

Another important feature of new cars fitted with run flat tyres is that they have a tyre pressure monitor system (TPMS) which informs the driver when they have a puncture. This is especially useful in the case of slow punctures which may not immediately be obvious when driving the car.

A big additional advantage of cars with run flat tyres is that they do not typically come with spare tyres (we will explain why later in the article), so they have a reduced overall weight. This improves fuel efficiency and handling while creating more boot space.

Whilst there are clearly some big advantages in using run flat tyres, there are a few minor disadvantages you should be aware of:

1. Comfort - You may occasionally experience increased vibrations when using run flat tyres. This is due to the stiffer sidewalls on the tyres, which have less flexibility when dealing with imperfections on the road.
2. Cost - A run flat tyre will usually be more expensive than a standard tyre. So, if it does get damaged, the cost of buying a new tyre will be relatively high.
3. Performance - Another minor downside of the stiffer sidewalls is that they can reduce the car's ability to handle corners and slightly reduce braking times.

Here are four key ways to help identify a run flat tyre:

1. ISO symbol - All run flat tyres are marked with an International Organisation for Standardization (ISO) symbol. This can be found on the sidewall of each tyre and consists of the letters RSC (Run Flat System Component) surrounded by a circle.
2. Tyre markings - In addition to the ISO symbol, run flat tyres also have other markings on their sidewall. These markings will vary, but acronyms such as RFT (Run Flat Technology), SSR (Self Supporting Run Flat) and ROF (Run On Flat) will tell you that the tyre is a run flat.
3. Personal manufacturer designations - Some tyre manufacturers use bespoke terms to identify their range of run flat tyres. For example, all Pirelli run flat tyres will have the words 'Run Flat' written on the sidewall.
4. Vehicle specifications - If you are in any doubt as to whether or not you are using run flat tyres, you can always check the owner's manual or any specification documents provided by the manufacturer.

Broadly speaking, run flat tyres allow you to drive for around 50 miles after the puncture occurs as long as your speed does not exceed 50 miles per hour. Your drive will be bumpier and stiffer than you are used to.

Please note that run flat tyres are not designed to be driven long term. They will deteriorate after you have driven a short distance and become dangerous. So make sure you immediately drive to your desired destination (be that a garage, your home or somewhere else) and arrange to have your tyre replaced.

It is important to know that a run flat tyre needs to be fully replaced rather than repaired. This is because mechanics cannot identify any secondary signs of damage to run flat tyres, so whilst they may be able to repair the primary cause of the puncture, the tyre is still not necessarily safe to use.

Run flat tyres always need to be replaced with a like-for-like run flat tyre. Using a standard tyre will reduce your traction and control when driving and generally compromise the performance of the vehicle.