November 9, 2006
While the variety of vehicle naming conventions for today's Sport Utility Vehicles, Sport Activity Vehicles, All Activity Vehicles, Multi Purpose Vehicles and Crossover Vehicles may be somewhat confusing, at least it remains clear that the vehicles equipped with four-wheel and all-wheel drive systems are ideal candidates for wintertime driving on ice and in snow. However when these vehicles are tuned primarily for on-road performance, they are also likely to be originally equipped with summer or all-season tires.
By design, summer tires are developed to emphasize dry and wet road traction at moderate to warm temperatures (best suited to the 45- to over 100-degree Fahrenheit range). Summer tires are not suitable for use in snow or on ice, and their dry and wet traction falls off when they are operated in cold temperatures.
All-season tires are allowed to trade a little dry and wet road traction in moderate and warm temperatures to provide light snow traction in freezing temperatures (best suited to the 20- to 100-degree Fahrenheit range). When relatively new, these tires are a good choice for drivers who only encounter occasional light snow.
Winter / snow tires are permitted to trade a little more dry and wet road handling in moderate and warm temperatures to emphasize wet, icy and snowy road traction in cold to moderate temperatures (best suited for 0- to 45-degree Fahrenheit range). Winter / snow tires are not intended for use in summer conditions, and their dry handling can't match that of all-season or summer tires.
However, since packed snow and ice are typically the slipperiest conditions drivers will face, they are the most challenging for tires. In order to get a better understanding of how much ice traction is provided by summer, all-season and winter tire types for sporty light trucks (no matter what their manufacturers call them), we conducted an "Ice Rink Performance Drive" on the glare ice of a hockey rink.
We compared three Bridgestone tires designed for light truck use, including the Original Equipment Turanza ER30 summer tire, Turanza EL42 all-season tire and Blizzak DM-Z3 winter tire. We used 235/65R17-sized tires mounted on 17"x7.5" wheels. The Tire & Wheel Packages were fitted to our 2006 model year Porsche Cayenne test vehicles.
The Porsche Cayenne lists a curb weight of 4,784 pounds and its power is distributed through a Tiptronic automatic transmission with permanent four-wheel drive featuring Porsche Traction Management.
Porsche Traction Management (PTM) distributes power using a standard torque split of 38% to the front axle and 62% to the rear; however, up to 100% of the torque can be delivered to either axle depending on driving conditions. PTM sensors continuously monitor steering wheel and throttle positions, as well as vehicle speed and lateral acceleration before determining the amount of power distributed to each axle. If one of the tires begins to lose traction, PTM uses the Cayenne's Automatic Brake Differential system to apply braking on that wheel, transferring torque that would otherwise be delivered to the slipping tire to the opposite tire instead. If both tires on one axle begin slipping, the Cayenne's electronic engine management system reduces power to reduce wheelspin.
In order to quantify the traction provided by each type of tire, we recorded the time it took for each of the Cayennes to cover 60 feet (to the center of the rink) while accelerating as fast as tire traction would allow. Due to the confines of the hockey rink, braking forces and cornering capabilities would be judged subjectively.
The Cayenne's Porsche Traction Management divided the engine's horsepower between the V-speed rated summer tires, and the vehicle's acceleration time of 4.0 seconds was on a par with a rear-wheel drive sedan equipped with winter / snow tires. For that matter, the summer tire's performance appeared acceptable until its cold temperature traction resulted in the longest subjective stopping distances and lowest cornering capability.
The T-speed rated all-season tires provided a noticeable improvement over the summer tires. While their 3.4-second time (about a 15% improvement over the summer tires) was favorable, the all-season tires' cold temperature ice traction resulted in marginal improvements in subjective stopping distances and cornering capability.
The Q-speed rated studless winter / snow tires completed their run in just 2.9-seconds (about a 28% improvement over the summer tires). And even though the winter tire-equipped Cayenne was traveling faster at the onset of braking, the winter / snow tires stopped it with the greatest subjective breaking force and allowed the Cayenne to complete the cornering exercise with ease. In this case, the dedicated winter / snow tires gave the Porsche Traction Management system some real cold temperature traction to work with.
|Tire||60-foot Time Seconds||Traction Index*|
|Bridgestone Blizzak DM-Z3||2.9||100|
|Bridgestone Turanza EL42||3.4||86|
|Bridgestone Turanza ER30||4.0||72|
|*Traction Index identifies the relative performance vs. the best available (higher is better).|
While not surprising, the results show the substantial advantage the studdless winter / snow tires have over performance winter, all-season and summer tires on glare ice.
The right winter / snow tires can reduce the challenge of driving your car, van or SUV in snow and on ice. Remember Dad's advice, "Nothing like using the right tool for the job!" It's your choice, make it a good one!
The Blizzak DM-Z3 was developed to enhance a light truck's four-wheel drive systems to enhance their poor weather capabilities. So, if you want to maximize all of your light truck's winter capabilities, use Bridgestone Blizzak DM-Z3 technology to help provide the snow and ice traction you need.
The Turanza EL42 is a Standard Touring All-Season tire designed for sports sedans, sports coupes and selected sporty SUVs. It was developed to blend some of the looks and handling of a performance tire with the low noise and ride comfort associated with a passenger tire, as well as provide year-round traction, even in light snow. Read more.
The Turanza ER30 is Bridgestone's Grand Touring Summer tire often used as Original Equipment on sports cars, coupes, sedans and SUVs like the Porsche Cayenne. It was developed to blend looks and handling with good noise levels and ride comfort, as well as provide traction on wet and dry roads. Like all summer tires, the Turanza ER30 is not intended to be driven in near-freezing temperatures, through snow or on ice. Read more.
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