Safety is right at the top of the motoring agenda. After seat belts, ABS and airbags, car manufacturers have now developed active driving assistance systems, such as traction control and computer-controlled stability programmes. More recently still, tyre pressure monitoring systems (TPMS) have appeared as optional equipment, with a clear trend to standard fitment. Closely linked to this development, tyres with run flat capability are proving to be the next step forward in car safety.
Bridgestone realises the importance of raising the safety level for cars around the world and so has pursued ways to overcome the danger of a tyre deflating while you’re driving or changing a tyre next to the road. These efforts have resulted in the revolutionary tyre technology known as the Run Flat Tyre.
Run Flat Tyre technology does away with concerns about flat tyres. Bridgestone set out to design a tyre that enables safe driving from the point when a puncture occurs until the driver can drive the vehicle to a safe location.
The Run Flat Tyre
Ever wondered what happens when a tyre loses air? Well, a tyre that’s lost its air either through penetration or a cut to the tread or sidewall area can cause loss of control of the vehicle; alternatively the driver will have to stop to change the tyre. With Bridgestone's new Run Flat Tyre (RFT) Technology, Bridgestone can provide greater safety and comfort to vehicle users in South Africa and the rest of the world.
It's not difficult to see why more and more car manufacturers are fitting RFT tyres to their new models. The first safety benefit is that if a vehicle in motion suffers a rapid loss of tyre pressure, RFT enables the driver to continue driving and possibly avoid a potentially fatal situation. Secondly, RFT tyres enable the driver to leave an area of risk to continue the journey safely.
RFT also provides more comfort and convenience for the motorist. Within the specified speed and distance limits (Specified at 80 km/h for up to 80 km), the driver can either complete his journey or travel to the next qualified service station, with no worry about having to change a flat tyre.
The trademark “Run flat” tyre or “RFT’ belongs to Bridgestone, and the manufacturing plant in Brits is one of four in the world to start producing Run Flat tyres. Bridgestone South Africa is also the first local manufacturer to produce Run Flat Tyres for BMW as original equipment for their latest vehicles.
How does the RFT work?
The sidewalls of the RFT have embedded reinforced and heat-resistant rubber strips. These strips prevent the sidewalls of the tyre from collapsing in the case of air loss. The OE recommended EH2 rim further prevents the beads from slipping off, keeping them firmly in place. So you can safely drive in control and comfort to an area where the tyre can be changed.
Two of the areas RFT focuses on are rigidity and heat resistance, so that the tyre can support the weight of the vehicle with total air loss. Bridgestone's RFT meets this challenge with a combination of design, materials and construction changes that optimise the location, shape and physical property of each tyre component:
The sidewall is constructed with reinforced rubber, carrying the vehicle's weight at zero-pressure;
While the bead shape configuration itself is unchanged, so that the Bridgestone RFT is compatible with conventional rims, the bead wire is wider and reinforced, ensuring a secure fit on the rim even at zero pressure, and special bead filler with low heat generation is used.
When fitting new RFT to a vehicle please keep the following in mind:
Always ensure that the size is correct.
Confirm that you fit a RFT and not a conventional tyre with same pattern and size. Confirm that it is a RFT by checking the sidewall for the RFT mark.
Ensure the tyre is mounted to the rim by tread design. RFT may be Directional Tyres, where the direction of travel will be indicated with an arrow on the sidewall, or RFT may be Asymmetrical, which will be indicated on the shoulder with "Outside" and "Inside". The outside should always be fitted facing away from the vehicle or on the rim face side.
Confirm that Load Index and especially the Speed Symbol is the same as the original RFT that was removed. Tyres with the same size and pattern may differ in Load Index and Speed Symbol.
Changing RFT to Conventional Tyres
Bridgestone does not recommend changing the RFT to conventional tyres. Because of constructional difference it may influence handling and performance. Vehicles fitted with RFT in most cases do not have a spare tyre. If you wish to change to conventional tyres, it is recommended that you consult with your local Vehicle Dealer to obtain written confirmation. The Dealer must also include which tread pattern and sizes to fit if a conventional tyre is allowed.
Conditions of Repairing RFT tyres
Run flat tyres can be repaired as with other tyres. If the hole is in the belt or crown area, a mushroom plug repair can be done for temporary emergency measures, but the tyre should be replaced at the earliest possible convenience. Repairs can not be carried out in the shoulder or sidewall areas as with conventional tyres.
Some vehicles in our market are fitted with Tyre Pressure Monitoring Sensors only. The system works with conventional tyres and is there to inform the driver of a tyre that is losing pressure.
These sensors can either be a "Valve and Sensor Unit" or a Sensor strapped to the inside of the rim.
Special care is needed when mounting or de-mounting a tyre to a rim where a pressure sensor is used.
Please make use of our RFT dealers to assist in changing tyres with sensors.
Please advise the tyre dealer of any devices fitted to your vehicle or wheel.
RFT Dealer Network
In Case of Emergency
In case of a puncture on a RFT, can I substitute it with a standard tyre? Bridgestone does not recommend mixing RFT & standard tyres. But in the case of an emergency it is possible to fit a standard tyre to the car. But this can only be a temporary solution for a limited time. The standard tyre must also comply with recommended speed and load recommendation from the vehicle manufacturer.