Rubber Revolution

RUBBER REVOLUTION

AREVOLUTION IN TIRE

manufacturing is taking

place. bringing with it

changes that will improve tire

performance for highway and racing users alike. Pirelli calls its system “MIRS” and Michelin, barely admitting its existence, uses the designation “C3M.”

In 1984, Michelin began the previous revolution in tire design with its introduction of semi-radial construction. By eliminating relative motion between crossed tire fabric plies, this allowed tires to run cooler. Cooler rubber lasts longer, or you can use less of it for the same lifetime. The resulting more compliant tread region was able to lay down a larger footprint, giving more grip. We have enjoyed these benefits from all tire manufacturers ever since.

Making radiais is labor-intensive, stimulating efforts to automate tire building. This is now culminating in the Pirelli MIRS and Michelin C3M flexible production systems, which not only reduce costs but also out-ofround, imbalance and force variation (soft/hard regions in the construction). The uniformity of tires made by these processes allows less material to achieve necessary minimum thickness. The result is again lighter, more flexible, cooler-running tires.

Because of changes in the way the tread belt is applied, more freedom in choice of tire tread profile is achieved. Over the last 10 years, roadracers have complained of an inability to accelerate from full lean. One reason for this is that previously, tire contour was tightly linked to the “equilibrium contour” the tire carcass assumes as it is inflated during manufacture. This link has now been broken. Bead wires were formerly tightly bundled, requiring extra sidewall rubber thickness. Now, flatter bead wire distribution permits more sidewall flexibility.

Previous to last year, Michelin race tires were known for extremely high peak grip, but with rapid grip loss after peak. Now, they combine this high grip with controllable sliding, as well. A close look at rear Michelin race slicks reveals that they are now made in molds with 48 articulated segments. CW testers have recently been impressed with MIRS-made Pirelli sport tires. Big things are happening, and we have only scratched the surface on this story so far. Wonder what great new stuff the other tire-makers are up to...

Kevin Cameron