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Auto racing remains important for tire development

Phil Berg
Car Culture

On Ford’s wild $36,000 350-horsepower Focus RS four-wheel-drive compact car, notice the tires are similar to those that come on the newest Corvettes. They are called Michelin Pilot Super Sports, and since 2010 have been arguably the top standard for car nuts who enjoy high-performance driving on the new crop of racetracks that have sprung up for private member use.

The largest tire companies and their automaker partners have continuously used racing as a development tool, and tire companies use racing as a direct test of exotic tire compound mixtures and shapes, which trickle down to use in street cars.

The most famous race used is the 24 Hours of LeMans in France, a 3,000-mile-plus contest for sports cars and prototype sports cars. The direct benefit from lessons learned in the heat of competition are shorter stopping distances in dry and wet conditions, longer wear, lower rolling-resistance for better fuel efficiency, and better grip in corners.

Last month Michelin introduced to the media the latest evolution of the Pilot line, the Sport 4S, which is intended to replace the Super Sport as more sizes and applications to high-performance track cars are produced. At the introduction, Michelin allowed auto fans the chance to compare its new Sport 4S to competitor tires such as Goodyear’s Eagle F1, Pirelli’s P Zero, Continental’s ContiSport Contact 3, Bridgestone’s Potenza competitors.

In at-the-limit track driving, there were noticeable differences between all of the brands, which we tested on a short, twisty asphalt course in a parking lot at the private Thermal Club race track in Southern California. Back-to-back comparisons on identical BMW M3 sport sedans, the new Michelins increased my confidence how quickly I could drive without scaring myself.

Serious track-driving addicts will discuss these abilities with excitement, I believe.

The price for top performance isn’t cheap. The new Michelin Sport 4S sells for $257 each for a Focus RS, just $9 more than the previous Super Sports for the same size. Continental’s Contact 3 for an Audi will run $286 per tire, while the Bridgestone Potenza is a relative bargain at $215 for the Focus.

What you get for this are tires constructed with up to 20 different compounds, most of which are proprietary blends of rubber. Today’s top tires have different compounds and tread designs on their outside edges than inside edges, and that construction combines dry and wet weather abilities in a compromise.

Holding all this together are textiles such as synthetic polymer cords, steel filaments and material that bonds the rubber and silica filler. The silica, which entered tire design in the early 1990s, tames the rubber’s penchant for bouncing too much, and is considered second only to radial construction introduced in the 1970s as a major tire performance breakthrough, says Laurent Huc, a development engineer with Michelin.

Huc said the Sport 4S is made of 20 different material rigidities: “Rubber is in 15 components of the tire, and every component needs to work together. We have a specific process to put the right materials in the right place.”

That translates to safer tires on the road, says Michelin test driver Sarah Robinson. “The key is the shape of the profile, in terms of performance.”

She adds that the new Sport 4S improves braking ability by several feet over the Super Sport tire’s performance. “That doesn’t seem like a big deal. When it becomes a big deal is that ‘Oh my god’ moment, when you’re driving down the road and see a yellow light, then the person in front of you is (panic stopping), then all of a sudden you need to stop right then.”