By Collin Fat
Photos by Collin Fat
Forty SVR members attended the recent Performance Tire tech session hosted by Porsche Sacramento to learn about what goes into an N rated tire, different performance tire categories, and what is their best choice for a replacement tire. Guest speaker Patrick Degosei, from Pirelli Tire, and Stan Thilman from Tire Rack were on hand to lend their years of expertise and knowledge in tire development.
Patrick, who is an engineer by trade, has spent a decade in tire development working for several years developing tires for formula 1. He engaged in the development of Pirelli’s performance tire line that included the P Zero, Pzero Corsa and P Zero Trofeo tires. He was also instrumental in the development of Pirelli’s newest line of performance tires known as the Pirelli P Zero R.
Patrick Dragosei explains the construction of a Pirelli performance tire.
Patrick discussed the engineering of their tires from a tread design standpoint and the differences between an all season, summer, and track day focused tire like the Trofeo R and how the longitudinal groves in a tire help make evacuate water in the rain and how the sipping also works in getting the water out from under the tire.
He had several tires on display and you could see these differences firsthand with the Pirelli all season tire having lots of sipes and 4 longitudinal grooves for removing water. Looking at the more track focused tires like the Pirelli Trofeo Track without sipes and just 2 longitudinal groves for water evacuation. In addition, did you know that the more tread blocks a tire has the more prone these blocks are for deformation when stressed in on a racetrack and this leads to a squimish feeling?
He explained the use of oils in the tread compound and waxes in the sidewall to help the tire remain compliant and the differences in tread compounding between the various types of tires. I was not aware that carbon black, one of the main ingredients in tires, is not only used to give the rubber its black color but also instrumental in tire grip. The more carbon black in the tread compound the more friction.
Lastly, several questions were asked about tread wear and when to replace tires due to time. He remarked that if see you cracking in your side wall or on the spider marks appearing in the tread that it is time for a new tire. As the tires and rubber age, he explains that the tires dry out and become less compliant. Although the addition of wax in the compounding is important to help the rubber remain compliant, due to atmospheric conditions like the sun, and repeated cycles of heat and cold that the tires dry out and become less compliant.
Patrick was quite gracious to field questions from our members in attendance. Patrick did an excellent job and really got into the engineering and chemistry involved in producing a performance tire. He addressed the differences in a summer tire and a snow tire as having differences in their glass transition temperatures. Below is a definition of this interesting term:
The glass transition temperature of a winter tire is its glass point, which is the temperature at which the rubber compound begins to lose its flexibility and become hard and brittle, like glass. Winter tire compounds are formulated with a lower glass point, often around -60°F, to ensure they remain pliable and provide optimal grip in cold, below-freezing temperatures where other tires would harden and lose traction.
Why the “Glass Point” Matters
Tire grip is a function of the tire’s compound’s flexibility. The lower the temperature, the harder most tires’ compounds become, reducing their contact with the road.
Winter tires have a rubber compound with a low glass point, meaning they stay soft and flexible even in very cold conditions. This increased pliability allows the tire to conform to the road surface, even in snow and ice, providing superior traction for starting, stopping, and cornering.
For a summer tire, the glass point is just below freezing. If you drive on summer tires when temperatures are below 45°F, the rubber will harden, lose grip, and compromise safety.
Stan Thilman, from Tire Rack, explained that the entire line of new Pirelli rubber including their track focused P Zero Corsa track attack designed to compete against the Hoosier R7 is now available for those autocross and track junkies.
Stan Thilman from Tire Rack
Larry Reuter, service manager at Porsche Sacramento, informed the group that the dealership currently is offering a buy 3 get one free tire special and that he would beat any price you might bring to him on a new set of performance tires. He also reminded the group that both dealerships offer PCA members a 10% discount on service and parts.
Bryce McGrew took questions from the group regarding tire maintenance from topics like when to replace them and the importance of checking your air pressure, watching for cracks in the side wall that could result in a blow out and the importance of proper alignment as it effects tread wear. He also mentioned that his crew can do 4-wheel alignments and custom track alignments to your specifications. A standard 4-wheel alignment currently goes for $399 which is competitive with other independents.
I received incredibly positive comments from the members in attendance. All commented that they really learned a lot about performance tires. A few members were even seen talking to Bryce about coming in for a new set of tires!
This was our last tech session for 2025 and your club plans to do a few again next year. If you have a topic, you would like to explore regarding any system on your Porsche send me an email or come to our annual planning meeting in November.
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