Group Michelin expects run-flat tire sales to surge as car manufacturers start to fit them on higher-volume cars.
So far, run-flat tires have been confined mostly to premium or luxury models, such as Audi A.G.'s A6 and A8, BMW A.G.'s Mini Cooper or the Rolls-Royce Phantom.
But BMW's recent decision to make them standard on its new 1 Series is a breakthrough in volume, according to Michelin, which is one of the tire suppliers for the new entry-premium model.
Nissan Motor Co. Ltd. and Honda Motor Co. Ltd. also plan to use Michelin's Pax run-flat tire/wheel system, but other than the 2005 Honda Odyssey the firms have not yet officially specified on which cars.
``Run-flat tires sales are finally taking off,'' a Michelin spokeswoman said.
The Paris-based tire manufacturer expects Pax sales to reach 200,000 to 250,000 four-tire units a year by 2005.
In 2000, Michelin, Goodyear and Pirelli S.p.A. agreed to exchange run-flat technology and offer auto makers multi-supplier deals to reduce their business risk. Bridgestone Corp., Continental A.G. and Yokohama Rubber Co. Ltd. also manufacture run-flat systems using conventional wheels and tires with reinforced sidewalls.
Run-flat tires typically allow a motorist to drive a car with a punctured tire up to 125 miles at a maximum speed of 50 mph before repairing or replacing the tire.
Bridgestone is the main supplier of run-flat tires for the BMW 1 Series, but Michelin also supplies BMW with its zero-pressure (ZP) tires for that model, which goes on sale in September. BMW has capacity to build 150,000 1 Series annually.
The Pax system consists essentially of an elastomeric ring around the rim of the non-standard wheel inside the body of the tire. If the tire loses air pressure, the rubber ring supports the tire tread so the car can still operate at lower speeds. ZP tires have reinforced sidewalls to withstand the increased flexing of running when deflated.
BMW has been the industry leader in adopting run-flat technology. It first used it on the limited-edition Z8 premium roadster, which went on sale in the U.S. in 2000 and was discontinued last year.
A car with run-flat tires can be designed with more trunk capacity because the spare wheel, jack and tools are eliminated. But the weight savings is reduced because run-flats weigh more than standard tires.
Initially, four Pax tires weighed the same as five standard tires, so there was no net gain. But four Pax tires now weigh the same as 4.7 regular tires.
``We keep working on that weight issue,'' a Michelin spokesman said.
But French auto makers say Pax tires require a stronger chassis and suspension, which adds to manufacturing costs.
Tires also are so-called unsprung weight-mass that directly reacts with road irregularities without being softened by the suspension-so Pax tire/wheel units make it more difficult to provide a smooth ride.
Renault S.A. sold a few thousand of its first-generation Scenics with the Pax system, but doesn't intend to do so with the new Scenic. ``The value for money isn't there,'' a Renault spokesman said.
Peugeot-Citroen S.A. product planning chief Bruno de Guibert said the upcoming 1007 small car, which is aimed at the same buyers as the 1 Series, won't use run-flat tires. ``It's not a question of cost, it's a question of weight and comfort,'' he said. ``The technology needs fine tuning.''