| Tyre maker Goodyear is claiming a first for passenger car tyres by putting carbon fibre in its latest product. Joining the established Eagle range, the new variant uses carbon fibre in the construction of the outer sidewall and is marketed initially at high-performance saloon applications for North America.
Steel cords are the traditional material used to provide the strength required of the sidewalls. Reducing sidewall deflections benefits both handling and steering. Conversely, making the sidewalls too stiff can be to the detriment of ride quality. Keeping unsprung mass to a minimum is desirable, so this also influences how the tyre will be constructed.
Goodyear says that what it calls “ResponsEdge Technology” provides the best solution to this compromise. It says: “In the end, it is about finding the perfect balance of stiffness/weight ratio that yields the performance attributes we are targeting.”
Carbon fibre has a higher specific modulus than steel and will therefore provide improved stiffness for every gram added. By using it to reinforce the outer sidewall, while making the inner sidewall in a conventional manner, Goodyear believes that the new tyres provide increased responsiveness and handling without sacrificing a smooth, comfortable ride.
Predictably perhaps, these tyres will be more expensive to buy than if they did not contain carbon fibre, which raises the issue of cost-effectiveness. Sidewall stiffness could be raised simply, and more cheaply, by adding more steel cord, but with a weight penalty.
There is also a layer of Kevlar on top of the belt, in place of the more commonly used nylon. This material was selected to provide increased absorption of road noise because of its much greater elastic modulus.
Both Kevlar and carbon fibre are more commonly associated with applications from the aerospace, defence or racing sectors and Goodyear admits there is something of a “halo effect” for tyres. Auto tyres marketing manager Bob Toth says: “Among performance-oriented consumers, carbon fibre is recognised as a substance that raises the product to a higher status.” |
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