Think of The Thermal Club’s track surface as the ‘Coachella Valley Cheese Grater.’ No circuit on the IndyCar Series’ calendar shreds tires at a faster rate than the sharp aggregate found at the private Southern California road course, and the trend will continue this weekend as the facility hosts its first championship motor race.
With Thermal’s torturous track surface in mind, IndyCar is briefly stepping away from the new tire distribution policy it introduced at St. Petersburg, where teams received five sets of the softer and less durable alternate tires and five sets of the harder primaries. Thermal is back to an outlay of six primary sets and four alternates to give teams more of the longer-lasting tire compounds.
Working from a request by IndyCar to create a greater gap in performance between its road racing compounds, Cara Krstolic, Firestone’s chief engineer and director of race tire engineering and production, and her team made the changes, which were on display to great effect at St. Petersburg.
With alternates that were quick but struggled to survive more than a dozen laps, the disparity in compounds was evident, and with the same call for primary and alternate separation at the remaining road and street courses, Firestone has made changes specific to Thermal’s hungry 3.067-mile circuit.
“When we talked to IndyCar over the off-season, they said we need more interest coming out of the tires,” Krstolic told RACER. “So, anything that we could do to widen the gap and make the alternate truly wear out, as opposed to having an alternate that’s pretty much there over a full stint, which was just not going to provide very good racing.
“So what we went through for Thermal is a little bit of a different approach. Instead of trying to make the alternate softer, as we did at our street courses, what we’re doing is putting more toughness into the primary tire.
“Even last year at Thermal, you saw quite a bit of drop-off, even with the primaries. So instead of trying to make the alternate softer, we’re making the primaries more durable, just giving them a little bit more toughness, more temperature resistance. So you’re still going to have the difference between the primary and alternate, but not quite to the level that you would see at St. Pete or the other street courses this year.”
At last year’s non-points ‘All Star’ race at Thermal, teams used harder Firestone compounds designed for heavier hybrid IndyCars, but due to the series’ decision to delay the introduction of its energy recovery systems until July, there was a mismatch in vehicle weight — the cars were more than 100 pounds lighter than what the tires were designed to accommodate. That isn’t the case in 2025.