An increasingly popular choice on new vehicles, Run flat tyres (also known as Mobility Tyres or RFT) are characterised by their ability to support a vehicles weight in the event of a puncture or loss of tyre pressure. This safety design enables the driver to retain control of the vehicle and remove the need for a tyre to be changed immediately when tyre pressure is lost – meaning you can still drive to a tyre retailer for a replacement of the damaged tyre (subject to distance limitations).
Overview
Unlike conventional tyres that rely on pressurised air contained within a tyre to support a cars weight, run flat tyres can support the cars weight by themselves for a short period of time.
Available in two variants, Run flat tyre systems may be equipped with a hardened sidewall or an internal support ring that’s mounted to the inside of the rim. Regardless of which type you have installed, both of these systems can be driven on without stopping when a puncture occurs.
Under normal operating conditions, runflat tyres continue to behave just like conventional car tyres. Run-flats still contain air which helps lighten the load the run flat system has to bear, spreading the weight of the vehicle evenly on the surface of the road and maximising the contact area formed between the car and the road.
One limitation is that run flat tyres cannot be fitted to every make and model as the vehicle manufacturer needs to specifically design the car to fit run flats. To find out if your car it suited it’s best to speak with your local dealer.
Safety
Developed specifically with increased safety in mind, Runflat tyres help minimise the risks associated with a punctured tyre. A puncture often causes the driver to lose control of their vehicle as a tyres shape and structure changes as it deflates, however in the event of sudden deflation, vehicle stability and therefore driver control are able to be maintained with run flats.
It’s fair to say most drivers, at one time or another, will be inconvenienced by a punctured tyre. Changing a tyre on the roadside is laden with risks, especially when it occurs on the freeway, during peak hour, a busy road, at night and work needs to be carried out on the roads shoulder.
And whilst a puncture is usually more of an inconvenience and an unwanted expense, the dangers involved with a tyre failure at high speed are far more serious – such as losing control of the vehicle. Using air pressure, the sidewall of a conventional tyre is securely pressed up against the wheel, however once this pressure is lost the tyre will seperate from the wheel and fall into the well of the wheel/rim causing the driver to lose control. Run-flat tyres on the other hand have been designed to keep all components of the tyre secure and in place when damaged or without pressure.
Tyre Pressure Monitoring System
A Tyre Pressure Monitoring System (TPMS) is an essential piece of safety equipment for any vehicles with Run-flat tyres installed. As run-flat tyres are designed to minimise the difference in ride quality when a tyre is punctured, especially on the freeway where little cornering takes place it can be hard to know when a tyre has lost pressure.
In the event that the driver is unaware of the damaged tyre, they are likely to continue driving at a speed above the safety limit outlined by the tyre manufacturer. Therefore it is essential that a Tyre Pressure Monitoring System be installed in conjunction with run flat tyres so that the driver is alerted (usually on the dash) when any loss of pressure occurs.
Advantages
Convience
As previously stated, the core advantage of runflat tyres is there ability to function without air over short distances at low speeds, as they are able to retain their overall shape thanks to its built in rigid components. This rigidity helps the driver maintain control of the vehicle if the tyre loses pressure, and removes the need to change a tyre immediately.
No need for a spare
Generally there is no need to carry a spare tyre with run flats, this reduces weight and frees up space in the boot.
Increased safety
The ability to stay in control and continuing driving on a run flat tyre means there is no need for you to change the tyre in unsafe conditions, such as the side of a the road. Generally you can drive at 80 km/hr for around 80 kms but you should refer to the manufacturers guide for more information.
Cons
Harder ride
Compared to a regular pneumatic tyre the ride is much harder.
Increased cost
Run-flats cost roughly 50% higher than your regular tyre.
Availability
At the time of publishing, run flat tyres are only able to be fitted to late model luxury & sports cars that have low profile tyres.
Repairs
Run-flats may only be repaired where the tyre is re-inflated as soon as the Tyre Pressure Monitoring System (TPMS) dashboard indicator lights up as driving with a flat tyre can often damage the sidewall beyond repaire.
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