Auto Service World
Feature   June 1, 2007   by Jim Anderton, Technical Editor

Carbon Captured

Goodyear uses carbon fibre to create a new kind of performance all-season tire

These days we know that to be healthy everyone’s diet should include dishes rich in fibre. Fibre, especially carbon fibre, is also a great part of many other recipes from golf clubs to Boeing’s much anticipated 787 “Dreamliner.” In the automotive industry, carbon fibre has become the race car designer’s material of choice, so much so that it’s appearing in the aftermarket on spoilers, rear wings and even interior components. Carbon fibre is simply, hot.

Racers use it because carbon fibre is stiffer and as much as 70 per cent lighter than steel for a given application; and street-machine enthusiasts like it because it just looks cool. Tires, themselves major users of other fibres from nylons to aramids, would seem to be a natural place to put materials that are light and strong. Goodyear has done that with the launch of a new ultra-high performance all-season tire, the Eagle F1 All Season.

“Ultra-high performance” and “all-season” used to be an oxymoron. But as sports sedans from manufacturers like Lexus and Acura join sports car makers like Porsche in producing very fast vehicles, low-profile, large diameter rubber is a common OE fitment. With even pedestrian cars and some light trucks offering top speeds of 220 km/h or more, redesigning a conventional tire with a higher speed rating just isn’t enough. Consumer expectations of high levels of cornering power and the fast, low-profile look are essential ingredients in this segment, which Goodyear is targeting with the Eagle F1 All-Season.

The new tire’s most prominent feature is the carbon-fibre reinforcement, a technology that debuted with Goodyear’s “Eagle featuring ResponsEdge Technology” (yes, that’s the whole name, trademark and all) which uses carbon fibre reinforced outer sidewalls to give that product, a sport tourer, sharper turn-in without a serious penalty in ride quality. The new Eagle F1 All Season is a logical extension of that innovation with the carbon fibre in both sidewalls. The sidewall also contains Goodyear’s “PermaBlack” anti-browning compound and the obligatory rim flange protector.

While sidewalls are important, it’s tread that sells tires and the pattern in the Eagle F1 All Season is understandably a hybrid of high performance dry grip and all-season types. Goodyear defines it as two zones: the ultra-high performance zone at the shoulders and at the centre, with an all-season zone in two strips between. All tires are a compromise, and the Eagle F1 All-Season’s tread zones address the basic problems that confront all sporting rubber that has to function in cold and wet conditions. Within the tread, maintaining good heat resistance during hard summer driving must be balanced with the need for a tread soft enough to flex in the cold. Silica is the material of choice for strength with softness, and Goodyear uses it in the tread compound. The now ubiquitous cap ply underneath the tread is of DuPont Kevlar, the same material used in bullet proof vests, although in marketing terms, expect the carbon fibre to overshadow its role. That’s a shame, because Kevlar (generically it’s “aramid”, the way “Kleenex” is to “tissue”) is also super strong and light, making it ideal for holding an ultra-high performance tire together at Z-rated speeds.

That’s good, but on the tire wall, the stuff that you can see within the two tread zones includes large shoulder blocks and Goodyear’s “Aquachute” water channeling grooves molded into a pattern that makes tire look like a combination of the arrowhead “Gatorback” pattern with the circumferential grooves of a rain tire. Very low profile wide tires (on sports sedans especially) create a significant problem for aftermarket tire engineers because some vehicles can “tram line” or wander in straight ahead driving. Complicating the issue even more is the need for modern aftermarket UHP tires to fit front, rear and all-wheel drive vehicles. That’s more complex than it seems. Toe, for example, can be zero to toe-out on front and all-wheel drives and commonly toe in with rear drivers, and both Ackermann and roll radius will be widely different on applications such as the Porsche 911 Carrera and the Chevy Malibu SS. A continuous centre rib helps, as does the other major new “acronym” technology, “TredLock.” TredLock addresses the other major conflict (other than compound) between all-season and performance treads: siping. It’s essential to generate the biting edges needed for foul weather grip, but it’s a recipe for squirm and chunking in a sports tire. TredLock uses almost invisible cups and cones between adjacent tread elements, allowing each block to lock into its neigbour during cornering.

How does it all work? SSGM tested the Eagle F1 All-Season in a sampling of the tire’s intended fitments, from the Mazda RX-8 to big Lexus sedans, and in wet cornering, the tire does indeed behave like a good all-season radial. In the dry, it also corners flat with excellent grip, showing little shoulder wear after hours of serious abuse. In sedans, it’s quiet enough to allow windows-open cruising and the new sidewalls are compliant, offering a good ride for the level of dry grip available. This may be another benefit of the carbon-fibre sidewalls, since many high performance vehicles now use light alloy suspension components and wheels, making unsprung weight more important to ride quality in these machines. Turn-in is sharp and acceleration/braking is as it should be for the advanced capability of many of this Eagle’s intended fitments.

Gripes? The primary issue for this tester is that winter capability is intended for winters as they know them in the “Lower 48.” In Canada, no one should drive a sports sedan or sports car on wide, low profile tires in the winter. These are three-season tires, so dealers should be ready to dispel the notion that consumers can abandon winter products. What they will do that’s a real bonus for our climate, is extend the performance driving season well into the autumn and allow drivers to get off winter tires earlier in the spring, potentially extending the fun part of the driving season by perhaps a month over the calendar year. Would you trade off a little ultimate dry grip for another month of on-ramp antics in your Porsche? I would, and for owners of expensive performance cars, few have the ability, inclination or opportunity to extract the last hundredth of a “g” in handling. The Eagle F1 All-Season is, in a sense, the real ultra-high performance radial in Goodyear’s lineup: Better than the vast majority of drivers, more practical than many UHP radials which require high-speed front end setups and negative camber for best handling, and able to deliver more fun for more of the time in our short fair-weather driving season.

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