What is RunOnFlat Technology

Tyre Advice from HiQ

When a conventional tyre is punctured, air pressure is lost, the sidewalls collapse, heat builds up and tyre and rim are inevitably damaged. The outcome is serious loss of control and the vehicle cannot be driven safely until the tyre has been repaired or replaced.

RunOnFlat technology is exactly as it sounds - it allows your car to keep on running after a puncture or blow out, even when the tyre is completely deflated, for approximately 50 miles at 50mph.

The ingenuity behind this is all to do with the tyre's reinforced sidewalls. These revolutionary tyres have powerfully reinforced sidewalls with resilient rubber inserts that ensure the sidewalls do not collapse when deflated, and continue to support the weight of the car, even when the air pressure that normally does this job, is gone. Build up of heat is also minimised, and the driver is still fully in control and can safely drive the vehicle until repair or replacement is possible.

In fact, the driver in most cases will be unaware that a puncture has occurred and it is therefore essential that tyre pressure monitoring systems are fitted to the car to alert drivers, and immediately warn drivers of any significant loss of air.

Drivers will no longer have to worry about being stranded or late because of a puncture, or even worse, having to deal with dangerous blow outs. Changing tyres on the hard shoulder will also be a thing of the past, as will be having to wait for the rescue service to assist you. RunOnFlat will keep you on the road and make sure you reach your destination safely.

And… RunOnFlat is still evolving. As with previous milestones in automotive history such as ABS and airbags, it is hoped that one day, RunOnFlat tyres will be fitted as standard in all cars. It is currently available on certain models of cars that have been specially fitted with tyre pressure monitoring systems

What is a tyre pressure monitoring system?

Tyre manufacturers only recommend fitting RunOnFlat tyres to vehicles that have been designed for RunOnFlat tyres and are fitted with the vehicle manufacturer's Tyre Pressure Monitoring System.

There are two Tyre Pressure Monitoring Systems, classified Indirect and Direct. Both Indirect and Direct Systems detect loss of air pressure and warn the driver via a warning indicator. This is designed into the electronics display on the facia of the vehicle. Indirect and Direct Systems are fitted as Original Equipment by a number of vehicle manufacturers including VW Audi Group, Mercedes and BMW Group.

BMW Group are leading the market with the fitment of RunOnFlat technology as standard specification to new model instructions, including the new 1 Series and the new 3 Series. BMW believe 5 million RunOnFlat tyres will have been fitted to their vehicles during 2005 alone.

What is an Indirect System?

With an Indirect System, loss of air pressure is alerted from the ABS/ESP Sensors. Air pressure is not directly measured but calculated on the basis of tyre rotation, sending signals through to the vehicle's Central Control Unit via the ABS Unit.

Indirect Systems are fitted to vehicles including the Mercedes A Class, MINI and Mercedes SLK. Drivers are alerted to a puncture, or substantial loss of air pressure, by a warning signal on the vehicle's facia. This warning signal does not necessarily identify which tyre needs servicing. Indirect Systems are not as accurate as Direct Systems because minimum air pressure (approx 0.7 bar) is not always detected. However, with the majority of punctures this is not a problem.

As with a conventional tyre, vehicles fitted with this type of system require regular tyre pressure checks. Following fitment of a replacement tyre, it should be remembered that directional, asymmetric and composite tyres must be fitted correctly.

Indirect Systems do not require re-initialising since the ABS Unit detects any change and monitors accordingly.

Classification of tyre pressure monitoring systems

Direct Systems should be re-initialised when the air pressure has been changed, the wheel positions have been swapped or when new or additional sensors have been fitted. Some Direct Systems are re-initialised by driving the vehicle a safe distance. Other systems, (Schrader, Siemens, Pacific) may require an external diagnostic tool. It is important to refer to tyre and tyre machine manufacturers fitting instructions when removing and replacing a RunOnFlat tyre, to avoid damaging the wheel rim mounted sensors. In all instances, you should refer to the vehicle manufacturer's handbook for instructions.

What is a Direct System?

Direct Systems have wheel rim mounted sensors or valves inside the tyre/wheel assembly. The sensors recognise change in air pressure immediately, and transmit it to the vehicles Central Control Unit via the Tyre Pressure Monitoring Systems antenna unit. Original manufacturer approval sensors must always be used to ensure that the sensors perform their role in detecting changes in tyre air pressure. Direct Systems are fitted to vehicles including the Mercedes S-Class, BMW 7 Series, Renault Laguna and Maserati Quattroporte.

What are the advantages of having a car that is equipped with RunOnFlat tyres?

Changing a deflated tyre on the motorway or in an unsafe area can be very dangerous, in fact it can sometimes be a perilous job, especially at night. On some highways without side-strip it might even be impossible. It is not a pleasant job to change a tyre, especially in winter or in the rain. It might also prove to be a difficult job getting the heavy spare wheel out of a fully packed boot. With RunOnFlat tyres you are able to continue your journey even with a totally deflated tyre. You will be able to drive for around 50 miles. This should provide enough time to drive home or to reach the next tyre or car dealer.

With RunOnFlat technology you don't have to drive around with the usually required heavy spare wheel, which will reduce petrol costs.

RunOnFlat tyres fit on standard wheel rims. Tyre or car dealers don't need special fitting tools.

Why do I need a pressure warning system?

A tyre-pressure warning system notifies the driver if the inflation pressure of any tyre drops below the pre-set warning pressure. RunOnFlat technology has such high levels of safety that if sudden pressure loss occurs it may be unnoticed by the driver and therefore the use of a low-pressure warning system is essential. The vehicle's manual will provide more information on this system.

Can I order RunOnFlat tyres for my new car?

Yes, if tyres with RunOnFlat technology are part of the approved accessory list of the respective car manufacturer you can make use of this new safety technology on your new car.

Can I put RunOnFlat tyres on my car that was originally not equipped with RunOnFlat tyres and where RunOnFlat tyres are not part of the official accessory list?

Tyre manufacturers recommend not putting tyres with RunOnFlat technology on cars that have not been developed for this new technology.

When I bought my car it was equipped with RunOnFlat tyres. Now I would like to replace them with standard tyres. Is this possible?

Yes, you can replace RunOnFlat tyres with standard tyres. You just shouldn't mix the two different technologies. However, tyre manufacturers don't recommend that you replace this safety technology with a standard technology. Any RunOnFlat tyre should be replaced with a RunOnFlat tyre of identical type, size and speed rating.

Do I have to maintain RunOnFlat tyres?

As for any other tyre, the inflation pressure should be checked regularly and corrected if necessary. Too low inflation is the leading cause of tyre failure. Pressure checks should be made when the tyres are cold. The vehicle's manual indicates the recommended inflation pressure. Only a professional car or tyre dealer should handle the damage inspection, mounting, dismounting, repairing or replacing of the tyres.

Can RunOnFlat tyres be repaired after a puncture?

Tyre manufacturers recommend that RunOnFlat tyres be changed after they have been used under deflated conditions. However, they understand that customers might want to repair their RunOnFlat tyres for cost reasons.

Unless otherwise specified in the car owner's manual, RunOnFlat tyres can be repaired by a qualified tyre professional after a thorough inspection and analysis of the tyre history. In case of doubt the tyre should not be repaired. The professional who is going to repair the tyre will be responsible for his work.

Tyre manufacturers don't support tyre repairs…

  • outside the tread area
  • if the inside or outside of the tyre sidewall area has been damaged by a sharp object
  • if the tyre has been run at low or zero pressure for a distance longer than recommended in the vehicle's manual or at a higher speed than recommended. The driver has to provide the necessary information.
  • if the inner liner looks damaged or rough
  • if there is any damage that would make a standard tyre not repairable