It’s true that changing a flat tyre is an important life skill to have, but the idea of a ‘run flat’ tyre sounds pretty handy too! A run flat tyre - or RFT, is a self-supporting tyre that is constructed differently to a radial tyre. In the event of a puncture, an RFT can safely carry the weight of your vehicle for a short period of time, despite having little to no air pressure.
When a regular tyre experiences a puncture:
- There is a rapid loss of inflation pressure
- Steering control is generally lost
- You’ll need to pull over immediately to replace the tyre (if not, it will self destruct within a short period of time)
When a RFT experiences a puncture:
- There’s no rapid deflation
- Your vehicle can continue moving safely (despite the loss of tyre pressure)
- You won’t need to stop where you are to immediately replace it
An RFT is able to continue running, despite a loss in air pressure due to its complex construction. The tread face and rubber used for the tread of an RFT is the same as a normal tyre. With a RFT, it’s all about the sidewall, which is made of thicker rubber and has been reinforced to make it stiffer than that of a regular tyre. This is the section of an RFT that will bare the weight of your vehicle once the air pressure is gone. No matter where the puncture occurs, a RFT will work in the same way.
There are two main types of run flat tyres - self-supporting and auxiliary supported.
Self-supporting RFTs have a stiffer, tougher rubber. This can temporarily carry the weight of the vehicle under low tyre pressure.
Auxiliary supported tyres don’t have a stiffer, tougher rubber. Instead, they’re attached to a special beaded rim that’s reinforced with steel and attached to the wheel. The bead fits between the two sides of the rim to keep air in the tyre and can support the weight of the vehicle.
In either instance, when an RFT experiences a loss in air pressure, you can generally drive your vehicle safely to a service centre, at a reduced speed of no more than 80 km/h to change the tyre at a potentially easier and more convenient location.
If your vehicle uses run flat tyres then you’ll need to replace your tyres with those that use run flat technology. RFTs need to be fitted to a specific rim, designed for use with the tyre. It’s worth mentioning that each manufacturer calls them by a different name. For example, Pirelli’s are ‘Pirelli Total Mobility (PTM), Michelin’s are ‘System’ (Pax) and Continental’s are ‘Self Supporting Run-Flat Tyres (SSR). When considering RFTs, it’s recommended that you speak with your tyre dealer.