Run flat tyres provide better resistance when a puncture occurs and can allow a vehicle to be driven when deflated.
They may also be described as self-supporting or auxiliary safety tires. Tyres with this technology have been around since the 1940s, but modern run-flat tires were developed in the mid-1970s with a tyre pressure monitoring system. A loss of inflation pressure does not immediately render the rim unsafe. Instead, the reduction in tensions causes an increase in the tyre's footprint (contact area with the road surface), which increases friction to allow continued motion down the roadway at speeds below 40 km/h. RFTs offer less vibration and higher rolling resistance than conventional tyres. When combined with electronic stability control, they reduce stopping speed and distance when compared to vehicles with traditional tyres in some cases.
The most common run flat tyres are pneumatics, but some solid rubber tyres are available. A rim flange reinforcement ring helps prevent wheel damage caused by excessive lateral forces generated during high/maximum speed driving or cornering. The wheel flange is original equipment connected to the wheel by steel spokes, which stretch or compress axially under load, which causes them to move apart laterally from each other due to torsion, resulting in a twisting force on the wheel at its mounting points, making the tyre secure. To resist this, strongly reinforced structures are needed within the wheel itself, usually, an aluminium alloy metal matrix composite structure is used for this purpose.
The run-flats tyre has a self-sealing sidewall designed to seal all but very large punctures, and the reduction of inflation pressure reduces the likelihood or extent of this run-flat type of damage.
Solid tyres are generally made from natural hard rubber, polymers such as styrene-butadiene (SBR) and styrene-isoprene-styrene (SIS); fabric cords such as rayon; and steel wires such as nylon, aramid fibre (Kevlar), aluminium alloy metal matrix composites, steel/steel cord and multiple plies of mixed textile materials. Manufacturers use different blends depending on the end-use application and distance limits. The flat tyre becomes a structural component that supports part of the vehicle load.
Temporary use tyres are a specialised form of solid tyre used on aircraft and some military vehicles for operations where a regular run flat tyre or spare wheel would be unacceptable. They have a reduced loading while inflated in a vehicle search compared to an equivalent conventional tyre, typically resulting in lower inflation pressure limits and softer construction hence limited speed. Run flat options include both temporary use tyres with multi-ply polyurethane sidewalls or maximum traction solid rubber tyres that can run without air indefinitely at high speed.
Generally yes. The cost of replacing regular tyres is much lower than run flat tyres and the generally offer better control.
If you buy new wheels to use with run flat tyres, it may prove to offer better value for money as the wheels that come with them may be specifically designed or adapted to use run flat tyres. You will need to continue to monitor air pressure in run flat tyres as you would a regular set of tyres.