Hardly self-supporting: Until vehicle makers accept them, aftermarket growth for run-flat tires will be painfully slow to proponents

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Hardly self-supporting: Until vehicle makers accept them, aftermarket growth for run-flat tires will be painfully slow to proponents
Tire manufacturers have been talking about and demonstrating various incarnations of run-flat tires for more than 30 years. But the marketplace looks no more ready to accept this kind of technology now than it did three decades ago.

Resistance hasn't been noisy primarily because carmakers and consumers alike are pretty much content with today's trouble-free tires. As an example, comparatively few flat tires occur on a leased vehicle before the lessee turns it in for a new model. "Who needs a run-flat tire or, as an alternative, tire pressure monitoring devices?" they say.

But safety mavens say otherwise. Of recent notice is the blurb in The Tire Rack ads featuring the SmarTire USA low pressure monitoring system available for just $229. A decade ago, such systems cost thousands.

Add between $80 and $100 to that to have the unit installed on a consumer's vehicle, including mounting and balancing, and anyone can have a low pressure warning device. Further, the cost for a set of run-flat tires is typically $25 to $30 more per tire than a conventional tire, so cost is not the factor it was just a couple of years ago.

The quest continues but questions remain, some of them posed by tiremakers themselves. In a somewhat lengthy document issued jointly by Groupe Michelin, Pirelli SpA and Goodyear Tire & Rubber Co. at the Geneva Motor Show in 2001, the three agreed that a PAX system (one of several run-flat type systems) would not be successful until the following aftermarket requirements were met:

1. a network of well-equipped sales and service outlets staffed by personnel with specific training in PAX system technology;

2. a 24-hour assistance service to motorists anywhere at anytime even on public holidays;

3. a toll-free number through which motorists can ask any questions relating to the PAX system.

Other requirements included having the proper tire mounting machines in place combined with refresher training courses. Some of that work has begun, but not all of it.

A Detroit snapshot

DaimlerChrysler, which fitted Goodyear's EMT tires to its Plymouth Prowler in 1997, continues to provide that vehicle, now the Chrysler Prowler, with the same tire. Beyond that, DaimlerChrysler has not added EMT tires, or any other type of run-flat system, to its line-up.

At the Ford Motor Co., the Lincoln Continental, announced recently as a cut-back victim, continues as the lone entry offering a run-flat as an original equipment option: the Michelin MXV4 Zero Pressure. This history dates back to model year 1994-1995.

The story is similar at General Motors Corp., where the Chevrolet Corvette, equipped with a low-pressure warning device and Goodyear EMT tires since 1997, remains the lone GM vehicle fitted with run-flat tires as original equipment.

What's the holdup?

The dynamics of a run-flat tire give vehicle engineers cause to pause. "They are heavier than a conventional tire, and the sidewalls of a self-supporting run-flat tire are very stiff," says Tom Long, a senior project engineer, tire development, for General Motors.

"This adds to unsprung mass, a higher chassis load and subsequently more ride harshness. When a driver experiences an event like a major pothole, the force transmitted into the body of the car is 25% to 50% greater than it would be compared to a conventional tire."

Why, then, does the Corvette ride on run-flat tires? "Because that vehicle is a showcase for technology," says Long. "It features not only run-flat tires, but a low-tire pressure monitoring system that tells the driver which tire is running low on pressure. It is a high-end car with all the high-end options, and it has been equipped with low-profile, stiff sidewall tires for years."

According to Long, the process of moving toward run-flat tires and the next step, a PAX-like system as advocated by Michelin North America Inc., is going to be evolutionary, not revolutionary.

"There are other issues as well. First, it must be explained to our General Motors customers that we require him or her to drive on a flat tire for 100 or 200 miles at a relatively low rate of speed in order to get that tire repaired or replaced. Further, we must tell them that there is no spare in the trunk. It is a psychological barrier that consumers may or may not buy into."

Taking the next step

"We are going to equip the 2004 Cadillac XLR, two-seat, luxury roadster (in photo) with the PAX system," says Long. "Both the tires and wheels will be vehicle specific and that will tell us what kind of aftermarket or consumer backlash is out there."

Although not a skeptic, the engineering side of Long shows through. "Right now I can change a tire in less than five minutes," he says, "but with the PAX system, it will take me 20 to 30 minutes.

"We know also that when any tire loses air, including run-flat tires, the vehicle is much more difficult to control. As engineers, we are already being asked to add vehicle dynamics in braking and yaw control on some models. But doing so adds weight and price to the cost of the vehicle, something consumers don't like."

General Motors already has placed these devices in 14 of its 2001 model year cars, including the Buick LeSabre, Buick Regal, Buick Park Avenue Ultra, Impala LS, Monte Carlo LS and SS, the Oldsmobile Alero and Aurora.

There are now two million GM cars on the road with low pressure warning devices on board as original equipment; more may come depending on what tire safety laws are created by the National Highway Traffic Safety Administration (NHTSA) under the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act.

NHTSA has proposed requiring 2004 model year cars to be equipped with tire pressure monitoring systems. However, the U.S. Office of Management and Budget (OMB) recently ordered NHTSA to review the proposal. It remains to be seen whether the OMB's decision effectively kills the original proposal.

Both Ford and DaimlerChrysler have little to say when it comes to discussing run-flat systems. A Ford spokesman revealed only that all 2003 Ford Expeditions, Ford Explorers and Lincoln Navigators will be equipped with low-tire pressure warning devices. The Jaguar XK 8 may come equipped with a similar device.

A DaimlerChrysler spokeswoman says the Chrysler Prowler is the company's only vehicle with OE run-flat tires (Goodyear's EMT tires).

GM answers the big question

When will we see most new cars equipped with a PAX-like system? "We are a long way off from seeing all vehicles equipped with a system like this," says Long. "I think it will be five to 10 years before we know what will be acceptable to consumers, the aftermarket and manufacturers.

"As manufacturers, we are responsible for making sure this system works under all circumstances, and that will take time. One thing that is known is that the PAX system has a ride advantage over the self-supporting run-flat tire because the PAX system tire is basically conventional in nature.

"Still, PAX system tires and wheels are much higher in mass than conventional tires and wheels. In fact, they may never be as mass efficient as conventional tires."

'No special wheels'

Tom Janello, special projects manager for Continental Tire North America Inc., says the one-time darling of the future, the ContiWheelSystem (CWS), similar to the PAX system, has been shelved in favor of run-flat systems that don't require special wheels.

"The OEMs asked us to do that," says Janello. "We will be announcing a new self-supporting run-flat tire in April of 2002."

The new tire will feature technology from both Continental and Bridgestone/Firestone Americas Holding Inc. (BFAH), which, per a recently signed technology agreement, are jointly developing the run-flat technology.

Janello says Continental is sharing its safety ring technology with BFAH, while BFAH is sharing some of its self-supporting tire technology with Continental.

Remaining under development at Continental is the CSR, or Conti Safety Ring, that slips into a conventional tire and onto a conventional wheel. "When a tire loses its air and is running at zero pressure, the ring supports the load," he says. "It is something we have had under development for the last three or four years, before signing the technical agreement with BFAH."

Janello says the CSR system will be OE on a European carmaker's upscale, limited production vehicle in the fourth quarter of 2002 and will appear in the U.S. market in about a year.

"We believe the CSR system, with its conventional tire and conventional rim, can and will be a nice match for mass produced passenger cars, vans and SUVs," says Janello. "The OEMs can eliminate the spare if they want to or keep it in the trunk, as is the case with the Lincoln Continental."

Janello believes this technology on a mass-produced basis is still at least five years away, minimum. "It will require a cultural change in the way motorists think about their car, including their real or perceived dependence on the spare tire.

BFAH and run-flats

"When the OEMs asked us to produce a run-flat tire, we responded with the Firehawk SH30 RFT zero pressure tire in three popular sizes, the P195/60R15 87H, P205/60R15 90H and P225/60R16 97H," says Phil Pacsi, executive director of North American Consumer Tire Brand Marketing, Bridgestone/Firestone North American Tire LLC.

But according to Pasci, that tire has not caught on. "It has gone nowhere. It isn't moving because there is no demand and there won't be until the OEMs equip their vehicles with such tires."

BFAH has other run-flat tires in its arsenal, including the Firestone Firehawk SZ50 RFT for Corvette owners. On the Bridgestone side of things, the Potenza RE 040 RFT comes in just two sizes, but is OE on the Lexus SC 430, the Infinity Q45 and the BMW Z8, says BFAH. There is even a Blizzak MZ 03 RFT offered only as a replacement run-flat in a 245/40ZR18 93Q size.


The most recent run-flat news at Goodyear Tire & Rubber Co. centers on the BMW Mini Cooper, which will enter the United States in March 2002 equipped with Goodyear EMT tires for summer use only.

A company spokesman says the market for run-flat tires isn't doing much and won't until the OEMs and consumers create the demand. "Certainly, the technology exists; it is good and it is already in limited service," he says.

"For many years, the run-flat concept has been just below the horizon. But with word that the new Mini Cooper will arrive with Goodyear EMTs, we could be seeing the beginnings of the sun starting to peek over the horizon," says John Rastetter, director of tire information services for The Tire Rack in South Bend, Ind.

Much like the sudden popularity of the new Volkswagen "retro" Beetle a few years ago and, later, Chrysler's PT Cruiser, the Mini Cooper could well follow the same path, in Rastetter's opinion. "If it does, more and more consumers will learn about run-flat tires."

Monitoring run-flats

Rastetter says he carries a fairly substantial inventory of run-flat tires and does see subtle growth in the replacement market.

For the record, he prefers the type of low-pressure warning device that actively reads each wheel position and lets the driver know the air pressure in each tire.

"A driver needs to know if one tire is low because of a severe drop in ambient temperature. An ABS-type system won't tell a driver if his tires all lost 2 psi during the course of a week. It reads them all the same and may not show an air loss when all four tires are losing air at the same time.

"It must also be understood that the run-flat part of our industry is still in its relative infancy in terms of actual use. Trying to find the answers to questions from a single source is not there yet," says Rastetter.

So as tiremakers, vehicle manufacturers, equipment makers, tire dealers and consumers await final decisions from NHTSA about the use of low pressure monitoring systems, the widespread use of run-flat tires inches slowly along.

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