PARIS—Group Michelin is launching a second generation of its Energy line of low-rolling-resistance passenger tires in Europe, promising more all-around performance—including all-weather type traction—while reducing rolling resistance another 5 percent. Although it stopped short of calling the upgraded Energy range all-weather or all-season tires, Michelin is labeling the new products ``R+W''—Road & Winter—and marking them with a special symbol depicting the sun over a bank of clouds from which rain drops and snow flakes are falling.
The company emphasizes the new tires cover all the accepted performance criteria of summer tires while providing motorists traction in ``certain wintry conditions.'' Michelin already is delivering tires of the new generation to original equipment customers, and plans a widespread aftermarket launch across Europe throughout the spring.
The new range—two T-rated and one H-rated designs—replaces the MXT and MXV3A launched in the European replacement market in 1992-93. In the intervening period, Michelin has produced more than 50 million units of Energy-branded tires, which promise a 15-percent reduction in rolling resistance.
The Michelin Energy XT1 and XT2 are T-rated, asymmetric tread-patterned replacements for the MXT range. The XT1 covers tire widths up to 175mm and has two circumferential drainage grooves for the 145mm and 155mm widths, and three grooves for the 165mm and 175mm sizes; the XT2 is a separate pattern for tread widths of 185mm and more, and features four grooves.
The H-rated XH1 also features an asymmetric tread pattern with four circumferential grooves.
In general, the new tires outdo the existing Energy range in the following areas:
Improved grip on damp, cold and ``lightly'' snow-covered roads;
Lower weight (an average of 10 percent); and
Reduced rolling resistance (at least 5 percent).
The new products achieve their improved wet grip and limited winter mobility through a combination of the effects of a silica-reinforced tread compound, the asymmetric tread designs and new siping techniques.
Asymmetric tread patterns, pioneered by Michelin in 1965 with the XAS, address the conflicting demands on a tire, i.e., assisting steering and transmission of torque.
Efficient steering, according to Michelin, requires a rigid tread with a low siping ratio, especially in the outer shoulder. Power transmission, on the other hand, is best handled by a tread design that provides efficient water clearance and anti-aquaplaning characteristics.
In addition to modernizing the asymmetric tread pattern concept, Michelin is using three new siping techniques to fine-tune the new tires' road-handling characteristics:
Quadrangular sipe—an elevated, total block edge length sipe that serves to pierce the water film surface;
Crankshaft sipe—a ``zig-zag'' shaped sipe that provides an imbrication effect to stabilize each tread block; and
Z-sipe—an accordion-fold-type sipe that provides aggressive wet weather traction while closing against itself in hard driving conditions (used on the XH1).
All-season tires have not penetrated the European marketplace to any great extent. Goodyear, the leading marketer of all-seasons, estimates annual European demand for these products to be about 1.5 million units, or between 1 and 1.2 percent of the replacement market for new tires.