Run flat tyres have become increasingly common on new vehicles over the past decade, particularly on premium and performance cars from BMW, Mercedes, Mini and others. But what exactly are they, what are their advantages and limitations, and what happens when one needs replacing?
What Are Run Flat Tyres?
Run flat tyres are specifically designed to remain functional for a limited distance and speed even after a complete loss of air pressure. Unlike conventional tyres which collapse immediately when deflated, run flat tyres have significantly reinforced sidewalls that support the vehicle’s weight at zero tyre pressure.
There are two main types:
- Self-supporting run flat tyres — the most common type, featuring reinforced sidewalls with additional rubber inserts that carry the vehicle’s load when deflated
- Support ring systems — a rigid ring fitted inside the wheel that physically supports the vehicle when the tyre loses pressure. Less common but used on some premium vehicles
How Far Can You Drive on a Deflated Run Flat?
Most run flat tyres allow continued driving for up to 50 miles at a maximum speed of 50mph after complete air loss. This is generally sufficient to reach a place of safety or a tyre fitting centre.
It is absolutely critical not to exceed these limits. Driving beyond the specified distance or speed on a deflated run flat can cause the tyre to fail suddenly and catastrophically — with potentially severe consequences.
You must have a TPMS (tyre pressure monitoring system) fitted to your vehicle to use run flat tyres safely — without it, you may not notice a deflation until serious damage has occurred.
Advantages of Run Flat Tyres
- You can continue driving after a puncture rather than being immediately stranded
- Particularly valuable on motorways and fast roads where stopping is dangerous
- Allow manufacturers to remove the spare wheel and jack, saving weight and creating boot space
- Generally more resistant to blowout when deflated, as the reinforced sidewall maintains tyre shape
Disadvantages of Run Flat Tyres
- Significantly more expensive — premium run flat tyres can cost two to three times the price of equivalent conventional tyres
- Firmer ride — the reinforced sidewalls make run flats stiffer, resulting in a less comfortable ride particularly on rough roads
- Limited repair options — many manufacturers recommend replacement rather than repair after a puncture, even where the damage would be repairable on a conventional tyre
- Not universally available — run flat tyres in less common sizes can be difficult to source quickly in an emergency
Can Run Flat Tyres Be Repaired After a Puncture?
This is one of the most common questions about run flat tyres, and the answer is nuanced. Many run flat manufacturers specify that tyres which have been driven on while deflated — even within the specified limits — should be replaced rather than repaired. This is because there is no reliable way to inspect the internal structure for damage after the tyre has supported the vehicle’s weight without air pressure.
If a run flat tyre suffers a puncture but has not been driven on while deflated (for example, if you notice the flat before moving the vehicle), and the puncture is in a repairable zone, repair may be possible. We assess each run flat tyre individually.
Can I Replace Run Flat Tyres with Standard Tyres?
Technically yes, but with important caveats. If your vehicle was designed for run flats, it almost certainly does not have a spare wheel or jack. Switching to conventional tyres without sourcing a spare wheel means you would be completely stranded in the event of a puncture.
Some vehicles also have suspension tuned for the stiffer run flat sidewall. Fitting conventional tyres can change handling characteristics. Always discuss this with a tyre professional before making the switch.
Run Flat Tyre Supply and Fitting from Mobi Tyre
Mobi Tyre supplies and fits run flat tyres across North Wales and border England. If you have a run flat tyre issue and are unsure whether repair or replacement is appropriate, call us on 07768 491888 — available 24 hours a day, no call-out charges.
