July 8, 2005
Many of today's highly refined sport utility vehicles look and drive more like luxury performance cars than a traditional SUV. BMW X-series, Cadillac SRX, Mercedes M-Class, Porsche Cayenne and Volkswagen Touareg are just a few of the vehicles setting new standards for the group. Rigid uni-body chassis, highly developed suspensions and significant power under the hood move these refined SUVs down the road swiftly in comfort and style.
But traditional passenger car or conventional light truck tires cannot deliver the blend of handling performance, ride quality and styling that the vehicle manufacturer designed their SUV around, or that its owner would be happy with. As an alternative, the Street/Sport Truck tire category offers a better fit featuring the modern tread patterns and lower sidewall profiles along with higher speed ratings to deliver the looks and performance that matches the needs of these new, refined sport utility vehicles.
How well do these tires really handle? And what about ride and noise comfort for that everyday commute to work or school? To get a better understanding of these tires and the potential trade offs in handling versus ride comfort, Tire Rack team conducted a Real World Road Ride and limited Performance Track drive to evaluate three performance-oriented tires from the Street Sport Truck category. Keeping with the "Refined Performance" theme, our evaluation used three identical 2004 V6 Volkswagen Touaregs, fitted with new, full tread depth 255/55R18 tires mounted on 18x8.0" wheels. We compared the Continental CrossContact UHP with the Michelin 4X4 Diamaris, both of which are summertime only tires, and Pirelli's Scorpion Zero, an all-season tire that is also an Original Equipment fitment on the Touareg's sister platform, the Porsche Cayenne.
Our 5.6-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.
One thing we did discover during our Road Ride, whether the result of highly developed tire designs, a very capable vehicle like the Volkswagen Touareg, or both, is that there were only minimal differences felt between the three tires in this evaluation. The Pirelli Scorpion Zero we used is an Original Equipment (OE) fitment on the VW Touareg's sister vehicle, the Porsche Cayenne. The other two tires, Continental's CrossContact UHP and the Michelin 4X4 Diamaris are designed for the replacement market, yet both performed similarly out on the road to the Scorpion Zero.
Our team was able to discern some subtle differences in road noise and ride quality. While the tread noise of each of the three tires was not considered objectionable, the Scorpion Zero tended to produce a subtle, higher pitched noise during steady speed driving, while the CrossContact UHP produced a lower tone. The Michelin produced a broader "white" noise, without the distinctive pitches of the other two. The 4X4 Diamaris offered good ride quality, and only became a little firm over the patched and broken asphalt sections of the evaluation route. The Scorpion Zero delivered ride quality that was rated to be almost as good as the Michelin, while the vehicle fitted with the CrossContact UHP seemed to be jounced around just a bit more when driving over the rougher sections of the route.
In the handling department, the Continental CrossContact UHP offered a small advantage in steering response, along with feeling a bit more sure-footed around the relatively fast highway off ramp. In this area, the Michelin felt nearly as responsive, while the handling of the Pirelli felt a little less precise than the other two.
Our 1/3-mile per lap test track includes 90-degree street corners, lane changes and simulated expressway ramps. Run in both dry and wet conditions, the test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers.
While rollovers can occur with virtually any type of vehicle, sport utility vehicles, pickup trucks and vans typically ride higher off the ground and have a high center of gravity. This makes them more susceptible to rolling over than performance or passenger cars if the driver loses control. Track testing vehicles with a high center of gravity requires proficient driving sensitivity and skills.
However, in order to learn more about the growing number of Street/Sport Truck tire category applications, Tire Rack has selected its most experienced drivers to participate in our dry and wet Test Track Performance Drives. While this reduces the number of drivers participating compared to passenger car tests, it does accurately compare the tires' performance capabilities at their limit.
On the track drive in dry conditions, our team felt small subjective differences that were not much greater than what our electronic timing system indicated. Overall, the Continental CrossContact UHP lapped our handling course the quickest of this test by a small margin and was found to offer the best handling balance and overall cornering performance of the group. The CrossContact UHP felt responsive, predictable and composed during all of the hard maneuvers of our course.
The Pirelli Scorpion Zero was a close second, feeling responsive on initial turn in, but not quite as "connected" as the Continental. This may be due in part to the Scorpion Zero's all-season compound and tread design, which can compromise summer's clear road handling somewhat in an effort to provide some wintertime traction in snow and ice. The Michelin 4X4 Diamaris was a close third, feeling stable and well balanced when pressed hard in the corners. This tire did not feel as if it had quite the overall grip as the other two tires, however.
In wet conditions, we found the Michelin 4X4 Diamaris displayed a small traction advantage over the other two tires. The overall grip level felt slightly better than the others, and proved to be just a bit easier to drive at the limit, resulting in a slightly quicker average lap time. All three tires lapped our wet handling course within 0.3 second of each other, indicating just how similarly matched these products are.
Continental CrossContact UHP (Street/Sport Truck Summer): The CrossContact UHP is Continental's Street/Sport Truck Summer tire designed for high performance four-wheel drive sport utility vehicles.
On the outside, the CrossContact UHP uses a silica-enhanced tread compound to combine wet and dry road grip with rolling resistance comparable to passenger car tires. The compound is molded into an asymmetric tread pattern that features solid outer shoulder blocks linked to a continuous rib combined with large, independent tread blocks that flank a circumferential center rib to provide directional stability and steering response. Lateral tread grooves are combined with four, wide circumferential grooves that provide efficient water drainage to reduce hydroplaning and enhance wet traction. Read more.
Michelin 4X4 Diamaris (Street/Sport Truck Summer): The 4X4 Diamaris is Michelin's Street/Sport Truck Summer tire that provides their highest level of wet and dry traction for luxury sport utility vehicles. Used as Original Equipment on the BMW X5 4.6is, Porsche Cayenne S and Cayenne Turbo, the 4X4 Diamaris is also available in the large rim diameter sizes appropriate for other light trucks.
On the outside, the 4X4 Diamaris molds a wet weather tread compound into an asymmetric tread design that features large outer shoulder blocks that contribute to steering response and cornering confidence. A continuous center rib enhances steering precision and high-speed stability while two wide circumferential and multiple lateral grooves channel water to reduce the possibility of hydroplaning. Internally, two high-tensile steel belts are reinforced by Michelin's BAZ technology (spiral wrapped nylon Banded At Zero degrees to tire rotation) to enhance stability at high speeds while improving tire uniformity and reducing weight to assure an even ride quality. Read more.
Pirelli Scorpion Zero (Street/Sport Truck All-Season): Derived from Pirelli's legendary P Zero performance tires, the Scorpion Zero is a Street/Sport Truck All-Season tire for sport utility vehicles and pickup trucks. The Scorpion Zero was designed to provide year round traction and handling for drivers who operate their light truck vehicles primarily on-road in various weather conditions, including occasional light snow.
Depending on tire size, the Scorpion Zero radial's tread compound is molded into a single Z or double Z (two rows of Z-shaped tread blocks situated side-by-side) intermediate tread blocks to provide responsive steering, along with enhanced cornering and braking capability. Lateral grooves and wide circumferential grooves provide water evacuation to resist hydroplaning and enhance wet weather traction. Pirelli Scorpion Zero tires combine high-speed precision with low noise levels. Read more.
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