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August 19, 2014

Run-flats: what a difference a decade makes

Tire makers strive for comfort as OE fitments increase; consumers are still not buying replacements

by Bob Bissler

Nokian Tyres offers the Flat Run line of run-flat tires for both passenger and SUV vehicles. The Hakkapeliitta 8 winter tire (pictured) also features run-flat technology
Nokian Tyres offers the Flat Run line of run-flat tires for both passenger and SUV vehicles. The

There seems to be love and hate relationships when it comes to run-flat tires (RFT). Auto manufacturers love offering the selling point of better fuel economy due to the lighter vehicle weight that run-flats offer by eliminating a spare tire. Consumers hate the high cost to replace original equipment run-flats and are struggling with their comfort level. Tire makers are caught in the middle.

We asked manufacturers to share their run-flat knowledge with us. There were 2 million replacement run-flats shipped in the United States in 2013 and 1 million OE run-flats. Manufacturers expect both numbers to increase in 2014.

While the number of OE run-flat fitments continues to rise, primarily on luxury vehicles, some tire makers are targeting the replacement market with more affordable run-flat options.

What does the future hold for run-flat technology in the U.S.?

MTD: How has run-flat technology evolved over the last 10 years?

Michael Mathis, president, Atturo Tire Corp.: The evolution has been quite gradual. We have taken advantage of the ability to support a larger SUV with our RFT AZ850. In general, run-flat technology has evolved to be applied to a wider range of sizes, particularly low-profile performance tires.

Robert Saul, senior product manager, Bridgestone Americas Tire Operations: We’ve focused our efforts on improving ride comfort in our latest generation of run-flat tires. In our newest run-flat offering, DriveGuard, we’ve used 3rd Generation, or 3G Run-Flat, technology to deliver a quiet, comfortable ride and confident handling of a touring tire. Bridgestone’s proprietary technologies, including our Cooling Fin sidewall design and NanoProTech sidewall reinforcement rubber compounds, have enabled us to make significant improvements over prior-generation run-flat tires.

Goodyear Tire & Rubber Co.: Self-supporting tire technology has evolved quite a bit over the past 10 years. Goodyear has a third-generation product that offers inflated ride comfort while still providing zero pressure capability. The concepts of yesterday and today are generally the same, but with a more refined balance between inflated and deflated performance.

Henry Kopacz, public relations manager, Hankook Tire America Corp.: Run-flat tires have evolved over the past number of years. New run-flat tire technology can be used to develop tires that do not sacrifice ride or comfort, a limiting factor for some consumers in the past.

Ron Margadonna, senior technical marketing manager, Michelin North America Inc.: With Michelin run-flat tires, we have strived to engineer our product with less mass for improved rolling resistance to meet tougher Corporate Average Fuel Economy (CAFE) standards without compromising any safety mobility performance. Also, we have generated a newer-type technology called ZP SR (Zero Pressure Short Range) to further enhance and meet OEM requirements.

Steve Bourassa, passenger and light truck products manager, Nokian Tyres Inc.: The reinforced sidewall concept, or self-supporting structure, of run-flat tires has remained essentially unchanged for over 10 years. Nokian continues to improve the comfort and rolling resistance of run-flat tires, despite how the weight of the tire and rigidity of the sidewalls work against these aspects of tire performance.

Steve Carpino, vice president of research and development, NAFTA, Pirelli Tire North America Inc.: In 2004, the run-flat concept was still very new. Back then, we had only one size in run-flat, the 205/45R17 for the BMW Mini. In 2004, only BMW was looking seriously at large-scale use of run-flats and designing their vehicle suspension systems around the concept. With those early run-flats, the internal  structure of the  tire provided a comfort ride level that would not be acceptable today.

In 2014, with a decade of research and development under our belts, we can adjust the tire design and sidewall thickness to get a high comfort level to match what OEMs are asking for while maintaining performance requirements and the run-flat mileage required. In most cases the typical consumer will not be able to tell they are driving on run-flat tires.

Maxwell Wee, director of sales, Sentury Tire Americas: The original idea for RFT was to provide extended mobility to vehicle operators. While this has not changed, other factors have come into consideration in response to consumer demand. The latest RFT tires have to provide extended utility while maintaining the comfort level of a regular tire. Manufacturers have responded with new sidewall and compounding technology that will do both. RFT tires are now available for applications on vehicles without the need for a special suspension setup.

Bob Abram, product planning manager, Yokohama Tire Corp.: The primary challenges on run-flat tires initially were price, harsh ride quality and, due to the fact that many of the original run-flat tires were summer UHP products, tread life. All of those issues have been addressed to some degree in the past 10 years, but probably not to the degree of ultimate customer satisfaction.

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