While fitment rates of run-flat tyres are increasing year-on-year, there is still more development work to be done.  Matthew Beecham reviews the run-flat market.

There are many factors shaping the global tyre market.  Over the last 20 years, the popularity of sport utility vehicles, minivans and crossover vehicles has steadily increased, prompting manufacturers to redesign their tyres.  Indeed, the increasing segmentation of the car market has led directly to a more complex tyre market.  In response, manufacturers have focused on ways in which to improve tyre dimensions, weight, rolling resistance, noise, and fuel efficiency. Social environmental awareness and advances in tyre technology will also play an increasingly important role in the definition of tomorrow's tyres.

Perhaps the most dramatic innovation in tyre technology over the past decade or so has been the development of the run-flat tyre.  Run-flat tyres are specially constructed enabling them to be driven on in the event of loss of air pressure. It means the driver can either drive home or to a garage to fix the tyre. Run-flat tyres allow a motorist with a puncture to drive the car up to 120 miles at a maximum speed of 50mph before repairing the tyre.

"We recognise that there are several outside factors that are increasing the demand for run-flat tyres, such as safety and the need to make vehicles lighter to reduce CO2 emissions," said Franco Annunziatto, managing director of Bridgestone's technical centre in Rome. "We also believe that the use of run-flat tyres is contributing to environmental sustainability. Cars with run-flat tyres have no need for a spare tyre, from the beginning to the end of the vehicles life."

For the automakers, equipping their vehicles with run-flat tyres enables them to offer security and safety benefits and, more significantly from a commercial perspective, a reduction in the overall weight of the car and an opportunity to optimise its load area. A car designed with a run-flat system can be designed with more boot capacity because the spare wheel, jack and tools are eliminated. The extra space also opens up further possibilities for hybrid and LPG fuelled cars. 

There are basically two types of run-flat systems.  The self-supporting and the support ring type.  The self-supporting run-flat tyre has reinforced sidewalls to support the load of the vehicle even after a loss of tyre pressure.  With the support ring-type system, a core ring supports the vehicle in case of air loss by fixing the tyre bead on the rim. 

Despite a slow start, manufacturers are reporting a brisk business for run-flats. Annunziato notes that although Bridgestone first introduced its SSR [self supporting sidewall run-flat] technology in 1986 on the Porsche 959, it was only in 1999 that the volume sales of run-flat tyres started. They were chosen by BMW as a standard fitment on several models.

Indeed, over the last six years, a number of automakers have added run-flat tyres on their vehicles, either as standard or optional fitment. These include Ferrari, Maserati, Mercedes, Toyota, Lexus, Mazda, Volkswagen, Audi and Nissan.

Despite progressive fitment rates, the run-flat tyre industry is still in its infancy, suggesting that there is still a lot more development work to be done.  Some argue that the characteristics of self-supporting run-flats are that they have a harsher ride, tend to be noisier, and as yet the automakers haven't been able to adopt the suspension sufficiently to hide those characteristics. 

"Goodyear has cracked the ride comfort issue with the latest RunOnFlat tyre," said James Bailey, corporate communications manager, Goodyear, about the company's tyre business. "Goodyear has sold more than 2.5 Million RunOnFlats in 2007 and the feedback of customers is extremely positive. Drivers appreciate the safety and convenience benefits Goodyear's RunOnflat technology provides. Most of our customers don't feel any difference between standard tyres and their RunOnFlat tyres. However, we know that some of our customers would appreciate "softer" tires for a higher level of comfort. Goodyear is addressing this demand with its new generation of RunOnFlat"  He added that the next generation of Goodyear RunOnFlats will have reduced chassis loading force and stiffness, improved comfort and reduced rolling resistance. "Recent Goodyear technology breakthroughs will take the current RunOnFlat technology to a new level."

For its part, Continental are concentrating on reducing rolling resistance, achieving higher comfort levels and improving the noise performance versus the current generation of run-flats. "This must obviously always guarantee the mobility after a tyre failure," said Nikolai Setzer, executive vice president, Business Unit Original Equipment, Passenger & Light Truck Tire Division, Continental AG.

In terms of tomorrow's run-flats, Setzer believes that everything depends on specifications issued by its OE customers and their strategy. "We are working on offering the widest possible range of EMS so the question is less: run-flat or spare wheel but rather: which EMS is the most valuable for the respective customer and its product."

Bailey reckons that automotive trends are leaning toward an integration of run-flats.  "Tyre Pressure Monitoring Systems are already mandatory in the US and might become mandatory in Europe as well. Hydrogen fuel cells and electric vehicles will require a strong integration of RunOnFlat tyres due to the packaging issues of these cars - with no space for a spare."

Over the next few years, manufacturers predict strong growth prospects for run-flats.  "We are convinced that the popularity of run-flat tyres will grow", added Annunziato. "There are compelling advantages of not needing to carry a spare wheel and tools, of knowing that you don't have to stop your car on a highway or a dangerous place, to replace a flat-out tire, of increasing luggage space and reducing the overall weight of your car. So our strategy is to improve the performance of run-flat tyres, and meet the needs of this projected demand."

Although the tyre industry would like to see almost maintenance-free tyres, it seems that we are a long way from that.  While run-flats offer a short-term solution, the ultimate is a penetration-proof tyre.  Could that really happen? The 'puncture proof' tyre has been the holy grail of the tyre industry for almost as long as it has existed. The sheer length of the search thus far suggests it could be endless. However, Bailey points out that Goodyear already has a solution.  "We already sell a truck tyre called the DuraSeal. It is OE fitment on the Renault Kerax off road truck. This has a gel-like material in the belt area that plugs punctures when exposed to air. The technology exists - but it does have a premium. This is meeting the needs of truck operators who are doing a lot of abrasive, off road work, but for car markets we see RunOnFlat as the best solution."

Meanwhile, Continental is in the throes of developing its own solution. "We are very close to reaching that goal with our ContiSeal technology which was developed exclusively for VW," concluded Setzer.  "This offers the driver 80% security against penetrations occurring through a tyre from the road surface. We are definitely headed in the right direction."

Matthew Beecham

Global market review of automotive tyres - forecasts to 2014

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