Unfortunately, at one time or another, most motorists will suffer the inconvenience of a tyre puncture.
There are inherent dangers associated with changing a wheel at the roadside. In particular, if the puncture occurs on a freeway where the work has to be carried out on the road shoulder, where possible motorists need to avoid the risk of being stranded.
While a puncture is usually more of an inconvenience and unwanted expense, the dangers involved with a tyre failure at high speed are far more serious, with the greatest danger being a complete loss of control of the vehicle. This occurs when the sidewall of the tyre, which is usually kept secure against the wheel by the internal air pressure, becomes separated and drops into the well of the wheel.
What are Run-Flat Tyres?
Run-flat tyres are designed to keep the all parts of the tyre secure and where they need to be, even when operating at zero pressure.
Compared to a normal tyre, run-flat tyres have a reinforced sidewall which stops the rim of the wheel touching the road, if the tyre loses all of its inflation.
While being subject to distance limitations, run-flat tyres allow the motorist to continue their journey without having to stop and replace the punctured tyre.
Types of run-flat tyres
Typically, run-flat tyre systems can be split into two categories:
Run-flat tyres with a strengthened sidewall
Run-flat tyres with an internal support ring that is mounted on the inside of the wheel rim
Although tyre manufacturers have adopted several different run-flat systems over the years, all run-flat tyres have one goal in mind - vehicle and passenger safety.
However, due to their limited popularity, only a handful of car manufacturers offer them as standard equipment, with the exception of BMW, which offers run-flat tyres as standard on most of their current models.
Run-Flat Tyre Limitations
Speed and distance limits: Although run-flat tyres allow you to continue onto to your destination with a puncture, you will be limited to a maximum speed of 80km/h for a maximum distance of 80km. The idea behind this is to give the driver enough distance to safely reach a service station to change their tyre.
Higher rolling resistance: Having a reinforced tyre wall makes the tyre heavier, which increases the rolling resistance. This makes the motor work harder to drive the car which decreases fuel economy. However, this is somewhat offset by not having to carry a spare wheel when you have run-flat tyres equipped.
Limited tyre options: Being not as popular as ‘regular tyres’, you will have limited options for which brands and run-flat tyres you can choose.
Limited vehicle options: Typically, run-flat tyre systems are pre-built into your vehicle, meaning that if your car came with run-flats off the factory floor, you can use them. On the other hand, if your wheels aren’t designed to accommodate run-flat tyres, you won’t be able to use them.
Tyre Pressure Monitoring System
The other essential item of safety equipment for a vehicle with run-flat tyres is a Tyre Pressure Monitoring System (TPMS). This system, typically only found on certain modern vehicles, lets the driver know when a sudden loss of pressure has occurred on one or more of their tyres.
When an alert is shown, that signals the driver that the run-flat tyre needs to be changed as soon as possible, either through a specialised tyre retailer or their vehicle manufacturer’s service centre.
Run-flat tyres are designed to minimise the difference in ride quality when a tyre is punctured. This is especially the case with freeway driving where there is relatively little cornering.
For this reason, it is difficult to determine whether a tyre has lost pressure or is operating in zero pressure conditions. Should the driver not be aware of a loss of pressure they may well exceed the safety limits imposed by the manufacturer.
There is a range of run-flat tyres which are deemed not repairable by the tyre manufacturer. If you are unsure, please check with your local Bob Jane T-Marts as to the specific manufacturer recommendations and pricing for your run-flat tyres.