|Bridgestone Potenza RE750 |
old directional design
|Bridgestone Potenza RE760|
new asymmetric design
Why asymmetric design.
Europe recent phased in new stricter noise standards over the past 5 years.
as found in a Tire Rack Technical article
E.C.E. standards have been initiated that require tire "pass-by" noise meet specific limits. These standards will be phased-in beginning in 2004, when tires fitted as Original Equipment on new vehicles intended for sale in Europe must pass noise emission testing, and will continue to expand in scope until 2009, when the standards will be applied to all tires sold in Europe.
The entire article which covers the Economic Commission for Europe's influence on the tire industry can be found at E.C.E. Tech Article
The directional tire design, with its v-shaped pattern to pump water out of the way, was presenting challenges in meeting these new standards.
The asymmetric tread patterns blend the different traction elements with different patterns across the face of the tread. The inboard side typically will have small independent tread blocks for wet (and snow if an all season) traction. The outboard side usually will consist of larger tread blocks or ribs for dry road cornering capability and increased contact patch.
In addition to lower noise levels, the asymmetric designs allow for multiple tire rotation patterns instead of the basic front to rear of the directional tires.
In summary, the new asymmetric designs are meeting and exceeding the traction levels of the directional patterns while reducing noise and allowing better rotation combinations.