RUN-FLAT TYRES: THE ULTIMATE SOLUTION TO PUNCTURES?
Wondering if it’s worth fitting run-flats on your vehicle? They may not be puncture-proof, but run-flat tyres do allow you to drive with a puncture for a limited time, making life easier and helping prevent accidents. However, run-flat tyres also have their disadvantages and are by no means a perfect solution. In this guide, we tell you all the pros and cons to help you decide whether run-flats are right for you.
As the name suggests, run-flat tyres are designed to keep working even when flat. To be more specific, run-flat tyres allow you to carry on driving with a puncture for 50 miles at a maximum speed of 50 mph. Run-flat technology compensates for the loss of air pressure in the flat tyre and enables it to continue temporarily supporting the weight of the vehicle without tearing or coming off its rim.
How does it work? It all depends on the technology used. The two most common run-flats on the market are:
Self-supporting tyres built with reinforced sidewalls which limit sagging when a puncture occurs. DSST (Dunlop Self-Supporting Technology) is one example.
Support ring system tyres fitted with interior reinforcement to prevent them from going flat if pressure drops. This type of tyre requires special wheel equipment. The Michelin ZP (Zero Pressure) technology uses this system.
Can my vehicle be fitted with run-flat technology?
Run-flat technology was initially only available for vehicles approved for run-flat tyres by their manufacturers (such as BMW, Mercedes and Mini) but has now become more widespread. Run-flat tyres can be fitted to all vehicles with aTPMS(Tyre Pressure Monitoring System) a technology which has been mandatory on all new vehicles since November 2014. The first manufacturer to offer run-flat tyres compatible with vehicles fitted with a TPMS was Bridgestone (Driveguard technology).
Why must your vehicle be fitted with a TPMS?
Drivers tend not to notice a puncture when run-flats are fitted. Unless you’re warned by your TPMS of a change in tyre pressure, you could carry on driving without realizing that you have a flat tyre.
The benefits of run-flats
Punctures are not an everyday occurrence but are a real inconvenience when they do happen, particularly at night, in the pouring rain or in a place where it is dangerous to stop. Run-flats undoubtedly make life easier by allowing you to drive to the nearest garage or safe place to change the tyre.
Another undeniable advantage of run-flat technology is that it allows you to keep control of your vehicle if you have a puncture. Nevertheless, you will still need to drive carefully. Also be aware that run-flat technology does not stop punctures.
In conclusion, run-flat tyres make your driving experience easier and safer.
The limitations of run-flats
In the past run-flats have been criticised for being less efficient than conventional tyres. However, performance improvements in terms of handling, driving comfort and rolling resistance mean that this is not so much the case today. Although slightly heavier than a conventional tyre (roughly 300g), the difference in terms of fuel consumption is minimal.
The main disadvantage of run-flats is that they are expensive:
Run-flats cost 20-30% more to buy than conventional tyres.
You always have to fit four.
A flat or damaged run-flat tyre cannot generally be repaired.
Fitting a run-flat can cost slightly more because special techniques are used.
Also, don’t forget that once a run-flat has been punctured, its performance will be limited. As soon as your TPMS warns you of a problem, you will need to reduce your speed to 50 mph and replace the tyre as soon as possible.
Finally, run-flat tyres offer a less comfortable driving experience than conventional tyres.
How to recognise a run-flat
Each manufacturer uses its own run-flat terminology. Here are the main names for run-flat technology:
DSST (Dunlop Self-Supporting Technology): Dunlop
EMT (Extended Mobility Technology): Goodyear
FRF (Federal Run Flat): Federal
HRS (Hankook Runflat System): Hankook
K1, K2, KA, KS Run Flat: Pirelli
LHD RFT (runflat and left-hand drive): Bridgestone
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