Continental ExtremeContact DW,
Extreme Contact DWS, and Extreme Winter Contact

It's an undisputed fact that your car's tires represent the single most important component in terms of vehicle handling. Upgrading your tires for the type of driving you're aiming to do is the most effective vehicle upgrade you can make. Upgrading tires for dry, warm-weather maximum performance is one thing. But when temperatures and weather conditions start heading south, choosing the right tire for the scenario will still make all the difference in terms of handling, acceleration and braking performance.

When you're talking really cold temperatures, snow, and icy conditions, tire selection becomes even more critical. Continental Tire has a few weapons in its cold-weather arsenal to help you push through whatever adverse environment you may face.

First up are the ExtremeContact DW and ExtremeContact DWS. The DW is Conti's ultra-high performance offering in the all-season category, designed for superior performance in both dry and wet conditions (hence the D and the W), as well as maintaining ride comfort and improved gas mileage. The DWS is designed for performance for both the dry and the wet, as well as in snow (S). Each features chamfered edges and a solid outer shoulder for enhanced performance on dry surfaces, a high void-to-tread ratio and enhanced groove curvature for excellent water evacuation in the wet. There's also what Conti terms "Dynamic Temperature Distribution," which is intended to reduce distortion for enhanced energy delivery, lower rolling resistance and improved tread life.

Speaking of tread life, both the DW and DWS incorporate a feature called Tuned Performance indicators. These are truly useful for the everyday consumer who might not necessarily know when the tire's tread has run the course of its usefulness in certain conditions-namely Dry, Wet and Snow. The indicators are visually apparent letters (you guessed it, D, W and S), stamped into the second rib of the tread, intended to alert the driver of the tire's current optimal performance levels. S indicates the tire is at optimum depth for use in the snow, W indicates suitability for use in the wet, and D indicates suitability for dry conditions. It's a pretty ingenious system that utterly takes the guessing game out of gauging the tire's suitability for whatever road condition that confronts you.

So why offer two variants of the ExtremeContact tire? Doesn't "all-season" mean the rubber is suitable for all road conditions? Definitely not, and we had the chance to see why earlier this year in a particularly frigid and snow-covered remote section of southern Montana. We had the chance to test this new rubber on fairly flat and solid but utterly snow and ice covered driving venues. Naturally we were able to test the Conti rubber against competing products from other manufacturers, and all superfluity aside came away mightily impressed, but we also had the chance to test the DW against the DWS in about an inch of powdered snow. The S in DWS is important. It indicates this tire incorporates one extra feature: special traction grooves and what they call Increased Pattern Edges for improved performance over-wait for it-snow-covered roads. The increase in traction and handling acuity between an all-season tire and a specialty snow tire is actually quite astounding. If you live in an area that's guaranteed to see some sort of snow stick to the ground, the DWS is the tire you're going to want.

The third offering in the lineup, brand-new for the 2009/2010 winter season, is the ExtremeWinterContact. This tire is engineered for use in the most extreme winter conditions, and areas that are guaranteed to not only see sustained weeks or months of snow and ice but also extreme low temperatures. Features include elevated lateral grooves which result in a stiff tread pattern for dry handling, and inclined longitudinal grooves to deliver greater driving force for outstanding traction and braking on snow. Multiple gripping edges contribute to this latter consideration, and the tire is created with a high-tech flexible tread compound and a high sipe density, which work in tandem to deliver reduced braking distances, even on ice.

One other thing about using tires in cold weather-running the proper rubber compound is critical, possibly the best reason of all to select a tire like the ExtremeWinterContact if running in frigid road conditions is an inevitable prospect. You don't want something that's inherently stiff, or something that stiffens up in very low temperatures (like a soft summer tire might). A good winter tire, like the EWC, is contructed with a compound that retains flexibility even in very low temperatures, in order to maintain grip on cold, slippery surfaces-snow, ice, or even cold pavement.

The Continental ExtremContact DW, DWS, and ExtremeWinterContact are available now. -Karl Funke

Continental Tire

Wavetrac LSD
While most people think of cars being either two- or four-wheel drive, the fact is cars with open differentials are one-wheel drive. Very few cars come with limited-slip differentials. With engine power outputs constantly on the rise, the open diff has become somewhat outdated.

In the past, there weren't too many choices for aftermarket differentials. A specific car will usually only have a few different aftermarket diff makes available. Autotech Sport Tuning in Aliso Viejo, Calif., is about to make the market a little bit bigger. We recently tested out its new Wavetrac differential and came away impressed.

Wavetrac uses a combination of helical-cut gears and a unique "wave" coupling, a mechanically expanding center section that prevents loss of drive in unloaded conditions-something no other gear diff has. the wave coupling uses two rings that, in profile, have nesting waves and valleys. When an axle is, or is nearly, unloaded, the center sections turn relative to each other. One ramp climbs the other, pushing the side gears apart and into the housing, causing an axial load inside the diff. This internal load acts for all purposes like the wheel is still gripping, so the diff continues to bias torque to the other wheel instead of losing drive. Other gear-type differentials work in a similar manner up to the point of unloading an axle. Once that happens, the Wavetrac's difference really shines.

It's this central Wavetrac device that allows it to still function in near- or at-zero traction situations. Other gear LSDs will revert to operating as open differentials when there's little or no axle load, meaning that if one wheel is nearly or fully in the air, or the car is transitioning from acceleration to coasting, those other differentials do nothing; they lose drive altogether. The Wavetrac, however, will continue to drive the gripping wheel, even when one axle is unloaded.

Another unique feature is the diff's bias plates, which Autotech has designed for the bearing surfaces inside the differential. The plates allow for consistent operation over the differential's life. Generally, gear-type diffs run their gears in direct contact with the housing. This works well at first, but over time, material transfer and galling from the metal-to-metal contact creates varying friction conditions, which decreases the unit's effectiveness. Wavetracs use a carbon-fiber material designed to last the life of the car, and will perform more consistently since it eliminates metal-to-metal contact. For track use, the Wavetrac's bias ratio can be altered by changing to optional bias plates.

The housings are made from case-hardened steel billet; the internals are built from 9310 alloy steel, which is not only hard but has very good fatigue resistance. The whole thing is held together with legendary ARP hardware.

Our installation began at VW Specialties in Huntington Beach, Calif., with dropping the 02M six-speed transmission from a VW GTI. Transmission teardown and diff installation was performed at Cal Trans in Santa Ana, Calif., and VW Specialties bolted things back together.

Our test car had basic bolt-on upgrades installed that in our estimation pushed output to over 200 hp. An open differential would have spun a tire through second gear, and coming out of turns, it'd spin the inside front even in third gear. With the Wavetrac installed, we couldn't get one wheel to spin even in first in a straight line. But the biggest difference was in cornering. Even on a skid pad the car wouldn't spin a tire. Jabbing the throttle at high steering angles, right at the edge of grip, the inside tire wouldn't let go. If anything, it seemed to bite harder and tighten the cornering line. But the best part is that you barely feel the diff working. Some LSDs are very abrupt, making them tough to drive because they are so aggressive, going from open to bind in a fraction of a second. The Wavetrac works constantly to feed power smoothly to both wheels. Sudden lifts of the throttle still result in forward weight transfer, but you don't get that initial toss from the diff unloading as on traditional LSDs. It's possible to modulate the throttle to keep the car on edge without having to time the diff lock-up.

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