GREENVILLE, S.C.-Michelin North America is moving into high gear with its fuel-efficient XSE technology. The tire maker has secured two new original equipment fitments for XSE-designed and built tires and plans to begin introducing the technology to its replacement lines in early 1995.
XSE, according to Michelin, is a technical breakthrough that allows company engineers to make tires with improvements in wet handling and rolling resistance, without sacrificing other performance characteristics such as wear, ride and noise.
The tire maker calls the technology ``revolutionary'' and considers it the most important development since the radial tire, which it introduced in 1948.
The U.S. subsidiary of Groupe Michelin detailed plans for XSE-which stands for radial, safety and environment-during a series of tire technology workshops for auto and tire trade journalists at its headquarters in Greenville the week of May 2.
At the same time, the company showed off the latest advancement to its run-flat tire-a 60-series self-supporting version that will be offered as an OE option on an unnamed 1995-1/2 model-year domestic luxury car.
Two Chrysler Corp. cars-the 1995 Dodge Stratus and Chrysler Cirrus-will become the first domestic autos to be fitted with ``Green X'' tires, the name Michelin is using to identify tires featuring XSE technology.
The Stratus will come with either the Michelin XW4 in size P195/70R14 or the ``Green X'' MXV4 in size P195/65R15 89H.
The Cirrus will feature the ``Green X'' versions of the MX4 and MXV4, depending upon equipment level, in sizes P195/65R15 or P195/65R15 89H, respectively.
Michelin has not named all the replacement tires to receive XSE technology, although the MXV4 will be one of them, a company spokesman said.
The ``Green Tire'' made its U.S. debut recently on the North American-made 1994 Honda Accord EX, the European imported 1994 Audi 80/90, BMW 3 Series and most Mercedes Benz S Class vehicles.
Since the inception of XSE in Europe in 1992, Michelin has sold 4 million original-equipment versions of the tires worldwide.
Michelin said that tires made with XSE can deliver as much as a 35 percent reduction in rolling resistance, for a 5-7 percent improvement in fuel economy, while improving wet and snow traction.
This is accomplished, in part, by using silica in place of some carbon black in tire compounding, the company said. While silica provides problems of its own-such as complicating processing requirements and reducing traction and wear levels-Michelin said it has overcome these obstacles.
During the technology workshops, Michelin also unveiled a 60-series version of its run-flat tire that can travel up to 30 miles at 55 mph before failing.
The new run-flat radial, which will carry the designation ZP after the tire's name, is designed to provide adequate handling at zero pressure so the driver can get the vehicle off the roadway and to a service area, according to Mike Wischhusen, manager, product engineering. A tire pressure monitoring device is required to warn drivers of air loss.
The Michelin run-flat is constructed using a thicker sidewall reinforcement that will support the load as a column and not buckle in the event of air loss, Mr. Wischhusen said.
To combat the extra thickness, Michelin has used low hysteresis rubber and temperature resistant materials to minimize heat generation, which speeds tire breakdown. In addition, the company modified the crown area to maintain inflated performance equal to a conventional tire, and changed the bead to improve rim retention.
The tire requires a special wheel with a modified safety hump, which improves the tire's ability to stay on the wheel at zero pressure. While necessary for the run-flat tire, the wheel can be used with conventional tires and service equipment, Mr. Wischhusen said.
Earlier this year, Michelin introduced a version of the run-flat-the MXX3 AP-as an OE option on the Buggati EB 110, a high-performance automobile.
Those tires, in 40-series sizes on the front wheels and 30-series on the rear, can travel up to 300 miles at 55 mph before failing, the company said.
The 60-series runflat version, with its higher sidewall profiles, will make the tire available to more mainstream autos.
According to Mr. Wischhusen, the 60-series run-flat weighs more per tire than a conventional radial. But the weight of four such tires is still less than that of a jack and spare tire, which could be eliminated from the vehicle.