Run-Flat Tires: A New Standard Rising
In a few years, accidents due to tire blowouts should become a thing of the past, along with spare wheels and cumbersome jacks.
When J.D. Power and Associates asked thousands what they most wanted in a new vehicle, almost 90% said: run-flat tires, making these the most desirable feature by far.
These so-called run-flat, extended mobility, continuous mobility or zero-pressure tires can be driven at normal speeds, for some distance, without any air pressure in the event of a puncture, a deep cut or the ravages of just about any other road hazard.
By contrast, "self-sealing" tires use different methods to preserve inflation, but there is a definite limit to the severity of the damage they can incur. These tires simply cannot be driven without any inflation pressure.
In the Name of Safety
The original idea of an "anti-puncture" tire appeared in a patent request as early as 1892. In 1934, Goodyear introduces the Lifeguard safety inner tube that was designed to deflate progressively instead of "blowing out." After several attempts and experiments, Goodyear introduced the SST, the tire industry's first "self-supporting" tire, in 1978.
Italian tire manufacturer Pirelli teamed up with Goodyear in 1983 to show a special asymmetrical wheel designed to lock the bead in. The same principle was applied soon after to Dunlop's Denloc ultra high performance run-flat tires, created for Porsche's 959 supercar. The Denloc design was also used in endurance racing but required unique wheels that made its run-flat capability very costly.
In parallel, Michelin created the "Bib Mousse," a foam plastic insert that lets the tire roll on spite of pressure loss. It is still widely used on car and motorcycle racers in events such as the famous Paris-Dakar rally. World Rally Championship cars also use "mousse" tires on some events, but their use and effectiveness are limited, since the foam heats up quickly and degrades at sustained high speeds.
Technology and Regulation Evolving Quickly
Modern sports cars use very low aspect ratio tires (tread width divided by sidewall height) and ride comfort is not as big a concern on these as on other vehicles. A wide tread and low sidewalls generate maximum traction and responsiveness. A short sidewall is also easier to reinforce and flexes much less to begin with.
This made the Corvette a natural choice to pioneer run-flat tires as an option on 1995 models. Several sports cars have followed suit, running on tires made by all the major manufacturers.
Goodyear's F1 Steel tire was the first run-flat tire offered as standard fitment on a production model, the fifth generation Corvette, in 1997.
Because the vehicle's actual handling changes so little, the driver needs to be informed of any significant loss of pressure. Pressure monitors have always been essential with this type of tire, but they will soon become mandatory.
Air pressure monitors are mandatory with run-flat tires. One such product is a new Gentex mirror-mounted display.
Carmakers will effectively need to install such systems in all new production vehicles to comply with new rules stipulated by the [government].
These new regulations will mandate low pressure warning systems for all 2004 model year vehicles, among other measures. The act was, in part, a reaction to numerous tire failures involving sport-utility vehicles that were reported in recent years.
Because of this, more run-flat tires will invariably be fitted at the factory. Many luxury and performance models will get them standard, but family-oriented vehicles such as the all-new 2004 Toyota Sienna AWD is already equipped with true run-flat tires also.
The new 2004 Toyota Sienna AWD minivan is the first mainstream, family-oriented vehicle to benefit from the undeniable safety of standard run-flat-type tires.
Much research and development work is being done on highly-automated, ultra-precise systems to manufacture run-flat tires, notably those which are designed from the PAX system. Because of the specially-designed wheels they use, these also require specific installation techniques and tire-changing machines.
This cutaway photo of a tire using the Michelin-developed PAX system clearly shows the solid "ring" that supports the tire tread in the event of a pressure loss.
Numerous Benefits
With run-flat tires, there is no need for a spare wheel or a car jack, for that matter. This frees up space for luggage, lowers cost and saves some weight, which makes for a small gain in fuel economy.
The Chevrolet Corvette celebrates its 50th anniversary in 2003 but also its 10th model year as run-flat tire pioneer.
Several high-visibility models such as BMW's Z4 and Z8 sports cars, the aforementioned Chevrolet Corvette, the Lexus SC 430, the MINI Cooper and Cooper S, and the spectacular new Rolls-Royce Phantom are all equipped with run-flat-type tires. These have been engineered specifically in cooperation between the car and tire manufacturer along the vehicle's development process.
With wide tires, big wheels and a small trunk, BMW's exotic Z8 sports car is a natural for run-flat performance tires as standard fitment from day one.
Some "run-flat" tires are currently available as replacement units. But they are generally more rigid, heavier and more expensive than conventional designs of the same size, especially when you factor in the cost of a pressure-monitoring system.
Run-flat tires can also substantially affect ride comfort and the durability of some vehicle components in real-world driving. Suspension parts, most notably. Ideally, a vehicle's structure and suspension components should be designed for the very different nature and characteristics of run-flat tires, and vice-versa.
A New Age Coming
According to experts, all road-going production vehicles will eventually come standard with run-flat-type tires. The rules on mandatory tire pressure monitors for all 2004 model year vehicles, will trigger substantial growth in run-flat tire installation at the factory. Such a development meshes perfectly with manufacturers' intention to eliminate the spare wheel and all related paraphernalia from their vehicles.
All this is excellent news for all of us, drivers and passengers alike. A new driving safety paradigm is coming soon, thanks to emerging and interconnected tire technologies. It's a thankless job, being round and black, but tires will indeed keep the world turning for a long time still.
Current production vehicles equipped with run-flat tires:
Audi A8 (PAX)
BMW 3-Series *
BMW Z4
BMW Z8
Cadillac CTS-V
Cadillac XLR
Chevrolet Corvette
Dodge Viper SRT-10
Hummer H1*
Lexus SC 430
MINI Cooper*
MINI Cooper S
Rolls-Royce Phantom (PAX)
Toyota Sienna AWD (2004)
*optional
by Editors of MSN Autos Canada / U.S.
(remember that unsuccessful attempt at a 3 point turn in the Austin Powers movie ... he had this piece of drivable machinery and tried to turn it 360 in a hall-way ... LOL)
