Carmakers Cooking Up a Flat-Free Recipe
The all-wheel-drive model of the newly redesigned Toyota Sienna minivan has just about everything a shopper could want. A fully loaded version with a $30,000 price tag includes a sonar backup-warning system, cruise control that automatically keeps the van a safe distance from slower-moving vehicles, room for eight, 14 cup and bottle holders and separate front and rear entertainment systems.
Everything except a spare tire.
Instead, this Sienna is equipped with what the auto industry calls “runflats,” four durable Bridgestone tires that can keep going at freeway speeds for about 100 miles even after being punched full of holes -- giving a driver enough time, Toyota Motor Corp. and Bridgestone/Firestone Inc. figure, to find a service station to get them patched.
Most Sienna models still have a spare. But people ordering the all-wheel-drive version will be pioneers: Their vans are the first runflat-equipped family passenger vehicles sold in the United States.
It’s part of a quiet move by the auto industry to wean drivers from their century-long dependence on spare tires. In recent years automakers have eliminated the spare in a handful of sports cars and luxury models to get extra storage space or to reduce weight for improved fuel mileage.
Since 1997, General Motors Corp.’s Chevrolet Corvettes have come with four runflats and no spares. Runflats are standard equipment as well on DaimlerChrysler’s Dodge Vipers, most of the new Q45 sedans from Nissan Motor Co.’s Infiniti luxury brand and a raft of cars from BMW -- the new supercharged Mini Cooper S, the Z4 and Z8 roadsters and the Rolls-Royce Phantom. Runflats are an option on the SC 430 roadster from Toyota’s Lexus division, and this spring GM will use them on the new Cadillac XLR roadster.
Because the tires run so smoothly even when deflated, these vehicles have an extra warning gauge on the dash to tell drivers that, say, their right rear tire is technically “flat” and they must get it fixed. Most runflats have a synthetic rubber insert in the tire’s sidewall that makes it stiff enough to support the tire temporarily even when it loses all its air.
“The spare should go the way of the hand crank on the engine” by the end of the decade, said Edouard Michelin, chief ex- ecutive of Michelin Group of France, which is aggressively pushing automakers to adopt its two runflat models as standard equipment.
Michelin, Bridgestone/Firestone and Goodyear Tire & Rubber Co. are all trying to persuade automakers that they can safely ditch the spare tire.
For motorists, the chief advantage of runflats is the ability to keep driving after a puncture until they can find a repair shop. One caveat is that runflats don’t work if the structural integrity of the tire is destroyed by a complete blowout. Runflats also cost about 20% more and present a stiffer ride, which may be fine for sports cars but is not so great for conventional sedans.
Automakers like runflats because eliminating a spare tire means getting rid of the jack, tire iron and extra wheel, and that means more room for passengers or cargo. And it can mean less weight, which translates into improved fuel economy.
“This has been the industry’s version of the quest for the Holy Grail,” said Bill Hopkins, vice president for product and technical planning at Akron, Ohio-based Goodyear. “It’s been slow, but we’re going to see a whole lot more of them coming as standard equipment on cars in the next five to 10 years.”
A Novelty for Now
But the auto industry has a long way to go before runflats make the leap from novelty to commonplace. Last year about 60,000 new vehicles were sold without spare tires, or less than 0.4% of the 16 million passenger vehicles sold in the U.S. For runflats to catch on, automakers must persuade customers to give up a security blanket that dates to 1906, when Henry Ford started selling cars with spare tires made by his friend Harvey Firestone.
Still, the auto industry has altered consumers’ tire-buying habits before, and it thinks it can be done again.
Those skinny “doughnut” spare tires that are limited to short distances and top speeds of 40 mph were introduced by Firestone in 1979. Automakers quickly saw them as a way to add storage space, save money and get better gas mileage. Today, doughnut spares are in 90% of passenger cars and 70% of minivans sold in the United States -- although most pickup trucks and sport utility vehicles don’t have them, because they might be unable to support a heavy vehicle.
Automakers also have discovered that big wheels, those with diameters of 16 to 20 inches, increase a vehicle’s visual appeal with many motorists. But providing spares with huge wheels also eats up space. Using runflats would solve that problem and allow designers to specify bigger wheels than were practical in the past.
“As a designer, I’d love to be able to do without spares,” said Dan Sims, head of Mitsubishi Motors Corp.’s North American design studio in Cypress. “It would give us so much freedom.” But Sims, like many others in the auto industry, believes it will be years before mainstream vehicles such as Honda Motor Co.’s Accord or Ford Motor Co.’s Taurus will be sold without a spare.
“There’s a lot of history there,” he said. “People are used to spares, and it will take time to persuade them that they can do without.”
The earliest cars, those sold in the late 19th century, came with solid rubber tires that made for a bumpy ride. Air-filled, or pneumatic, tires didn’t catch on until Ford and Firestone teamed up. Pneumatic tires solved a big problem for the fledgling auto industry -- they absorbed the bumps and jolts from potholes and rocks that riddled the rudimentary paved roads and made it relatively pleasant to travel by car.
But potholes and rocks, along with horseshoe nails, tree limbs, ruts and ridges, tended to poke holes in these thin rubber tires. And there was no auto club or roadside emergency service to come to the traveler’s aid.
So Ford and other early automakers mounted two or three spare tires on their cars, typically one on each front fender and one bolted to the rear. By the late 1930s, tread compounds and the strength of tire sidewalls cut the incidence of flats and motorists were able to get by with just one spare.
Tire construction has improved since then, as have the country’s roads. But tires still go flat. The Automobile Club of Southern California says its roadside assistance program received more than 500,000 calls last year to fix flats in its 12-county service area.
First Impressions
Thus far, the relatively small number of motorists who own cars with runflats seem to like them.
Jason Tani, a structural engineer in Thousand Oaks, bought his 2003 BMW Z4 in part because the two-seat roadster lacks a spare tire.
He wanted to buy BMW’s predecessor roadster, the Z3, but didn’t because of its minuscule cargo area. The spare tire all but filled the trunk. The Z4, however, lets Tani “pack my golf clubs and enough luggage for a long weekend,” he said.
Nor is the stiff ride a problem for Tani.
“This is a roadster,” he said. “It’s a sports car, and it’s supposed to be firm.”
Rebecca Zerbst, a physical therapist in Orange, says the runflat tires on her 2003 Lexus SC 430 roadster give her a sense of security “when I think of how I can still drive 50 to 100 miles on them if I get a flat when I’m by myself out in the middle of nowhere, like on a drive to Las Vegas.”
Where Edouard Michelin’s aim is to make runflats standard by 2010, others suggest it could take a little more time.
“We are going slowly and cautiously,” said Dave Wood, head of GM’s tire engineering group.
One reason is that tires and springs are the vehicle’s principal shock absorbers. And because runflats are stiffer than regular tires, they transmit a lot of shock from road bumps and potholes up into the passengers’ kidneys. So in heavier vehicles such as sedans, car engineers will need to alter suspension designs to handle runflats.
The tire industry began working on runflats in the early 1970s, but it wasn’t until the Porsche 959 sports car in the early ‘80s that a passenger vehicle was sold without a spare tire.
But Goodyear and GM get credit for the first mass- production model outfitted with runflats. In 1992 the Chevy Corvette offered runflats as an option; when the sports car was redesigned in 1997, GM decided to enlarge the cramped cargo area by ditching the spare and making runflats the standard.
In addition to winning consumer acceptance, a big challenge for tire makers is to develop runflats that will work on heavier pickups or SUVs, which together make up almost half the passenger vehicle market. These trucks need tires with taller sidewalls, and engineers have had problems designing a plastic insert for large runflats that is stiff enough to be self- supporting and supple enough to absorb road shocks.
Targeting Truck Market
A new runflat tire developed by Michelin could help bring runflats into the truck segment. Michelin say its patented PAX system has a plastic insert that is wrapped around the metal wheel inside the tire to support the tire if it begins to lose air pressure. Michelin says the overall cost to automakers for its new pickup and SUV tire is about the same as for a car equipped with runflats.
Goodyear and Bridgestone have licensed Michelin’s technology, and some in the industry believe the first pickups with runflats could appear within a few years.
Most consumers still know little about runflats because the industry has been quiet in marketing the new tires. But automotive market research firm J.D. Power & Associates in Westlake Village recently found that when told of the benefits of runflats, almost 85% of those surveyed said they would consider buying them with their next new vehicle.
“The tire industry is excited about the technology,” said Phil VandeWater, Bridgestone’s consumer products manager. “But it will take the automakers to spearhead things and push runflats to the next level by putting them on more and more vehicles.”
