When faced with a flat tyre, ideally you would stop and change to your spare tyre. However, (in South Africa especially) some areas may be too dangerous to stop.
In these situations, while you can drive on your flat tyre to the nearest petrol station or somewhere you feel safe – it is going to ruin your tyre and possibly the rims of your car. This is still better than risking your life or your safety, by stopping in an unsafe area!
A run flat tyre is a vehicle tyre that has been designed to resist the effects of deflation when punctured. Letting you avoid hazardous tyre changes and allowing you to continue the journey at a reduced speed. Run flat tyres have been described as the “first important revolution in tyre design since the invention of the pneumatic tyre.”
With low loads, one or two persons without luggage: approximately 240 kilometers at a maximum speed of 80 km/h
With moderate loads, two persons with full luggage or four persons without luggage: approximately 145 kilometers at a maximum speed of 80 km/h
With a full load, while towing a trailer or four persons or more with full luggage: approximately 48 kilometers at a maximum speed of 80 km/h
How does Run-Flat Technology work?
It is important to consider how a tyre loses air pressure and how the run flat tyre manages to ensure safety and continuous driving. A tyre loses air either through penetration or a cut to the tread or sidewall area, usually causing loss of control of the vehicle or forcing the driver to stop and change the tyre.
There are many different types of run flat tyres from a variety of tyre manufacturers. We can however identify 3 basic technologies:
Self-supporting: the tyre is built with stiffer side-walls that can bear the weight of the vehicle even when the pressure within the tyre is greatly reduced. The bead around the edge of the tyre is also specialized to grip the wheel rim such as to avoid becoming detached from the rim. The tyre’s side walls are usually made of an extra layer supported by a heat-resistant cord to keep the tyre in the original position even under the weight or road bumps.
Self-sealing: these tyres contain an extra lining within the tyre that self-seals in the event of a small hole due to a nail or screw. In this way, the loss of air is prevented from the outset so that that the tyre is either permanently self-repairing or at least loses air very slowly. ( Ultra seal – http://www.ultraseal.com/index.html )
Auxiliary-supported: in this system, there is an additional support ring attached to the wheel that can support the weight of the vehicle in the event of a loss of pressure.