January 25, 2008
2006 BMW E90 325i Sedan
In 1977, Goodyear introduced America's first all-season radial, the Tiempo, capable of delivering better snow traction in wintry driving conditions than the straight rib-style tread designs of the day. In doing so, Goodyear began a consumer evolution in the U.S.'s snowbelt states towards the use of year-round tires. However as an emerging, evolving tire category, all-season tires were often classified as such by simply meeting limited geometric tread design requirements.
As the all-season tire concept expanded from relatively narrow tires for passenger cars of the 1970s to wider, lower profile sizes to be used on the larger diameter wheels of the sports cars, sporty coupes and performance sedans of today, it must be remembered that all wide tires face greater wintry weather traction challenges because they need to plow a wider path through loose snow than narrower tires. Unfortunately it appears that these challenges aren't always met because Tire Rack's survey results of Ultra High Performance All-Season tires show that their wintertime performance doesn't always live up to an all-season promise.
In order to compare the differences between various tires, several members of Tire Rack team conducted tests in winter driving conditions by examining the snow performance of the four most recent Ultra High Performance All-Season tires our team experienced in dry and wet conditions in September of 2007. These tires included the Bridgestone Potenza RE960 A/S Pole Position, Goodyear Eagle F1 All Season, Michelin Pilot Sport A/S and Pirelli P Zero Nero M&S tires.
Our evaluation used 2006 BMW 325i E90 sedans with new, full tread depth 225/45R17-sized tires driven for approximately 600 road miles to break them in before we tested them back-to-back in the snow. All tires were mounted on 17x8.0" wheels.
We chose an oval track layout that uses the perimeter of our test track. One end of the 1/3-mile per lap oval features two 90-degree corners separated by a short straight, while the other end of the oval features a continuous radius sweeping 330-foot diameter corner. Before we began evaluating acceleration, braking and cornering capabilities, we groomed the snow to provide as consistent a surface as possible to minimize the variables associated with driving in snow.
Each driver initially ran three laps on each set of tires. While the vehicle's anti-lock brake system (ABS) was always operating, each driver's first two laps were run with the vehicle's Dynamic Traction Control (DTC) and Dynamic Stability Control (DSC) engaged, whereas their third lap was run with the DTC/DSC turned off. This way the drivers could experience the tires with and without the benefits of the electronic driver's aids. After the initial round of testing, we continued to drive laps as the originally smooth, packed snow surface became rutted and loose, challenging each tire's ability to provide traction, as well as to avoid following the ruts from previous runs. While testing traction and handling in wintry conditions is challenging because of subtle differences in the snow's moisture content, changing ambient temperatures and the sun's radiant heat, our results on this day were as follows.
The Eagle F1 All Season proved to be the easiest of these four Ultra High Performance All-Season tires to drive in the snow. It provided enough straight-line traction to allow the driver to smoothly build speed with only intermittent interference from the traction control, and slow without repeatedly engaging the ABS. However the Eagle F1 All Season tire's unique strengths were its more direct steering feel and greater cornering traction. This improved the vehicle's maneuverability and allowed the driver to place the car in the corners with relative ease and drive across ruts left in the snow by previous tires.
The Michelin Pilot Sport A/S provided a slight edge in straight-line traction that allowed the driver to build speed with little interference from the traction control, as well as slow without repetitively engaging the ABS. However, the Pilot Sport A/S didn't offer the steering feel or cornering traction of the Eagle F1 All Season and the car settled into predictable understeer as it negotiated our sweeping 330-foot diameter corner at its traction limit.
The Bridgestone Potenza RE960 A/S Pole Position provided satisfactory straight-line traction that allowed the driver to build speed with only intermittent interference from the traction control, as well as did a good job of slowing without frequently engaging the ABS. However, the Potenza RE960 A/S Pole Position couldn't match the cornering traction of the Goodyear Eagle F1 All Season or Michelin Pilot Sport A/S and also settled into predictable understeer as the car negotiated our sweeping 330-foot diameter corner.
The Pirelli P Zero Nero M&S proved to be the most difficult of these four Ultra High Performance All-Season tires to drive in the snow. The vehicle's traction control was often busy during acceleration and the anti-lock brake system was more easily activated during braking. While the P Zero Nero M&S couldn't match the snow traction level of the other tires when we started on a grooved surface, its snow traction dropped further behind them as the conditions evolved from groomed to loose snow.
Bridgestone Potenza RE960 AS Pole Position (Ultra High Performance All-Season): The Potenza RE960AS Pole Position with UNI-T AQ II Technology is the Ultra High Performance All-Season member of Bridgestone's Potenza family of performance tires for the drivers of sports cars, sports coupes and performance sedans. The Potenza RE960AS Pole Position is designed to provide year-round driving flexibility by offering predictable handling, traction and control on dry and wet roads, as well as in light snow. Read more.
Goodyear Eagle F1 All Season (Ultra High Performance All-Season): The Eagle F1 All Season featuring Carbon Fiber Technology is Goodyear's Ultra High Performance All Season tire designed to give sports car, sporty coupe and performance sedan drivers piece of mind in virtually any weather condition. It was developed to combine crisp responsiveness and confident handling with year-round traction, including in light snow. Read more.
Michelin Pilot Sport A/S (Ultra High Performance All-Season): The Pilot Sport A/S is an Ultra High Performance All-Season tire member of the Michelin Pilot family of low profile, high-speed tires. The Pilot Sport A/S was developed for the drivers of sports cars, coupes and sedans who desire year-round traction, including in light snow. The Pilot Sport A/S is designed to minimize dry and wet driving compromises while maximizing all-weather traction.
Pirelli P Zero Nero M&S (Ultra High Performance All-Season): The P Zero Nero M&S is manufactured for the North American market by molding an all-season tread compound into the non-all-season P Zero Nero summer tire's tread design. While this combination enhances the tire's dry road handling and comfort, it results in a scarcity of snow and ice traction enhancing sipes. Our experience has been that this tire is best suited for drivers who only encounter occasional light snow. In addition to the primary P Zero Nero M&S tread design compared in this test, Pirelli also uses an alternate "Pinna" nicknamed tread design that features additional siping to enhance snow traction for most Original Equipment (O.E.) applications. Read more.
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