Tires have come a long way in 25 years
Tires may be one of the most basic items on a vehicle, but they've changed quite a lot over the years.
Twenty-five years ago, tires were round, black, short and skinny. Now they are still round and black, but have gotten tall and chubby, much like their human owners. Like the eternal little black dress, the basic concept has never changed but the execution has changed remarkably.
In 2010, more than a billion tires were produced worldwide in about 400 tire factories. About 60 percent of that world output was by Bridgestone, Michelin and Goodyear, the big three.
In 1986, the best-selling cars were the Chevrolet Celebrity (P185/70R14), Ford Escort and the Chevy Cavalier, running on P175/80R13. For Michelin, the big seller was the XA4, an all-season tire with a projected tread life of 60,000 miles. That was a big mileage number at that time.
For Goodyear the big seller was the Arriva all-season radial, with sales of 3.9 million. And Goodyear pushed the edge of the performance envelope with the Eagle GT+4, the world’s first high-performance all-season.
The ultimate tire in 1986 was 50 aspect ratio, V-rated rubber for sports cars. In 1988 it took a Corvette with optional track suspension to generate .87 G on the skidpad. Today, the blandest of bland Toyota Camry comes OE-equipped with 55 aspect V speed-rated tires and can generate .79 G of grip.
According to Goodyear’s Bob Toth, “In 1986, Z and W and Y speed ratings did not exist, and V rated tires were reserved for the ultimate sports cars. In 1986, the Tire and Rim Association’s industry standards yearbook recognized only 65 total passenger car tire sizes, and no sizes were 17 inches or higher.”
He continues, “In 2011, the Tire and Rim Association’s yearbook recognized 330 total passenger car sizes. There are 59 18-inch, 23 19-inch and 25 20-inch sizes. ”
According to Michelin spokesman Sachin Despande, the most common size today for OE is P215/60 R16, and the most popular replacement tire size is P225/60 R16. Michelin’s bestselling HydroEdge tire is advertised as a 90,000-mile tire. That’s an improvement of 50 percent over 25 years.
Fitting for Canada, Bridgestone’s biggest seller today is the Blizzak, a studless winter tire introduced in the late ’80s that sells more units here in Canada than in the United States. Says Bridgestone spokesperson Elizabeth Lewis, “The Blizzak only debuted in Japan in 1988 so our most popular tire is part of an industry that barely existed back then.”
Just 25 years ago a 17-inch tire was too big to contemplate, but now many SUVs ride on massive 20- to 22-inch tires. The tire profiles have gone from 50 being low to half that. Today a 60 series tire seems just average. Mileage numbers for tread wear exceed 100,000 kilometers. We have tires that can run without air. In 1987, Bridgestone introduced its first generation of run-flat tires.
All these advances have come through extensive modeling of tires and road conditions on super computers. Computer modeling has answered the “what if” questions for engineers — “what if” we added this chemical; “what if” we changed the belts; “what if” the molecule of rubber were shaped differently. Finding such answers with prototype tires took too much money and too much testing time. Now tire engineers work at the nanometer level (one billionth).
Tire companies are altering how the various chemical elements in the tire link together, to make the product last longer, or be stickier, or both. Some tires use multiple tread compounds across the face of the tire, each for a specific weather condition. Goodyear’s TripleTred uses three.
Materials in the tires have evolved, growing both stronger and lighter; the weight of the tire has come down and the strength has gone up. Steel belts have replaced fabric cord. Less weight in the tire means better fuel economy and sharper handling. Goodyear makes extensive use of Kevlar in tires, as it’s stronger and lighter than steel, and is starting to make use of carbon-fibre. Lower tire weight has made lower profile tires possible.
In 1992, Michelin introduced the “green tire” concept. Marked Green X, it cuts rolling resistance by 25 per cent on average and results in an improvement in fuel efficiency of about 4 per cent. Michelin’s technological breakthrough was introducing silica into the tread compound. In 2009, Michelin produced its fourth generation of Green X tires with the Energy Saver A/S.
Alternative components are now used in creating tires. In 2008, Goodyear launched an environmentally friendly tire made with a cornstarch-based material. It partly replaces the traditional carbon black and silica with filler materials derived from cornstarch. Yokohama is using orange juice pulp in the company’s db Super E-Spec tires.
The last word from Goodyear’s Bob Toth: “Many things have changed in tires over the past 25 years; however, they remain underappreciated. After all, they are the only touch-points between your car and the road, so they’re vitally important.”