WHAT IS RUN-FLAT TYRES ?
Tyres That Help Maintain Vehicle Mobility...Even After Being Punctured
If you've ever been late for a date, appointment, or meeting because of a flat tyre, you already know how frustrating it can be. If you've ever changed a flat tyre in the rain, after dark, or on the shoulder of a busy highway, you already know how frightening it can be. So while we enjoy the freedom our vehicles provide, it's amazing how quickly that freedom vanishes when a flat tyre strands us.
Since the early development of the automobile, tyres have played an important role in determining a vehicle's overall comfort and safety. However, there are few consum
er products placed in harms way more often than our tyres, which encounter extremes in temperature, exposure to the elements, and attacks by debris on the road during their life. And while the tyre manufacturers' continuous research and development efforts have improved tire durability and longevity, only recently have they developed tires that can temporarily maintain vehicle mobility using standard Original Equipment and aftermarket wheels. These run-flat tyres provide the driver more flexibility when deciding where to have tyre repairs made.
Tyres don't typically carry the weight of our vehicles, the air inside them does. There are three basic elements which determine the load capacity of a tyre: the size of the air chamber formed between the tire and wheel, the strength provided by the tyre's construction to hold air pressure, and the amount of air pressure actually in the tyre.
Most flat tyres (and tyre "b
lowouts") are the result of slow leaks that go unnoticed and allow the tyre's air pressure to escape over time. Therefore, monitoring tyre air pressure in real-time gets us half way there. If we had tires that could maintain temporary vehicle mobility even after air loss, we'd be just about invincible.
Today there are three technologies used as Original Equipment on vehicles to help maintain vehicle mobility when a tyre is punctured. They are self-supporting tyres, self-sealing tyres, and tyres supported by an auxiliary system.
Self-supporting tyres feature a stiffer internal construction, which is capable of temporarily carrying the weight of the vehicle, even after the tyre has lost all air pressure. To provide "self-supporting" capability, these tyres typically attach rubber inserts next to or between layers of heat-resistant cord in their sidewalls to help prevent breaking the reinforcing cords in the event of loss of air pressure. They also feature specialized beads that allow the tire to firmly grip current Original Equipment and aftermarket wheels even in the event of air loss. Because self-supporting tyres are so good at masking the traditional loss-of-air symptoms that accompany a flat tyre, they require a tire pressure monitoring system to alert the driver that they have lost air pressure. Without such a system, the driver may not notice underinflation and may inadvertently cause additional tyre damage by failing to inflate or repair the tyre at the first opportunity. Typically, self-supporting tyres
maintain vehicle mobility for 50 miles at around 50 mph.
Examples: Bridgestone RFT (Run-Flat Tire), Goodyear ROF (Run-On-Flat), Michelin ZP (Zero Pressure), Pirelli RFT (Run-Flat Technology) and Continental SSR (Self-Supporting Runflat)
Self-sealing tyres are designed to fix most tread-area punctures instantly and permanently. These tyres feature standard tire construction with the exception of an extra lining inside the tire under the tread area that's coated with a puncture sealant that can permanently seal most punctures from nails, bolts or screws up to 3/16 of an inch in diameter. These tyres first provide a seal around the object when the tyre is punctured and then fill in the hole in the tread when the object is removed. Because these tyres are designed to seal the tyre immediately upon being punctured, most drivers will never even know that they just had a puncture. Also because these tyres feature standard tire constructions, the traditional loss-of-air symptoms that accompany a flat tyre remain to warn the driver if the tyre is damaged beyond repair. Therefore, self-sealing tyres do not require a low air pressure warning system.
Example: Continental ContiSeal. Pirelli Seal Inside
AUXILIARY SUPPORTED RUN-FLAT SYSTEMS ( NO LAUNCH IN MALAYSIA)
Auxiliary supported systems combine unique wheels and tyres used for Original Equipment vehicle applications. In these systems, the flat tire's tread rests on a support ring attached to the wheel when the tyre loses pressure. The advantage to this type of system is that it will place most of the mechanical task of providing run-flat capability on the wheel (which typically doesn't wear out or need to be replaced), and minimizes the responsibility of the tyre (which does periodically wear out and requires replacement). Additionally, au
xiliary support systems promise better ride quality because their sidewall's stiffness can be equivalent to today's standard tyres. The disadvantage to auxiliary supported systems is that their unique wheels will not accept standard tyres and that their lower volume will make this type of system more expensive.
Example: Michelin's PAX System wheels and tyres
Above Information Source from: http://www.tirerack.com/tires/tiretech