As RACER chronicled after Wednesday's official IndyCar test at Sonoma Raceway, Firestone's choice to use its Barber Motorsports Park tires on the northern California road course has led to unfavorable results with grip and longevity.
Teams found Firestone's primary Black tires, which they raved about at the grippy Alabama circuit, to deliver just a few laps of peak performance before taking a sudden nosedive on Sonoma's polished track surface. The rapid degradation left drivers scrambling for traction as their lap times increasing by as much as 2.5 seconds per lap once the nosedive occurred, leading at least one prominent strategist to question if extra stops will be needed to get through the race.
Engineers took time between Wednesday's test and Friday's pair of practice sessions to look for new chassis setup options to extend tire life, but the big drop-off persisted for an overwhelming number of teams. The most pressing concern is how Firestone's alternate Red compound, the faster of the two tires, will survive in qualifying. With extra grip at their disposal, teams tend to keeps their Reds tucked away during practice in order to preserve them for qualifying and the race, meaning almost every driver will have to wait until qualifying to discover how long the Reds will provide maximum grip. Could it be one lap of ultimate traction? Three? Five?
At this moment, no one knows, and it has led to a bit of anxiety with some of the better drivers in the field. The great tire longevity question will also have a direct impact on Sunday's race. Sonoma serves as one of the most challenging tracks on the calendar for passing, making Saturday's qualifying session especially important.
Qualifying at the front of the field is crucial for the championship contenders, but with the Reds serving as such a big variable, it's hard to predict what the Firestone Fast 12 – or the 85-lap GoPro Indy Grand Prix of Sonoma – will look like when they conclude.
Reigning IndyCar Series champion Ryan Hunter-Reay posted the third-fastest lap on Friday, and shared his thoughts on the question marks that hang over the entire field.
“It's tough predicting where the tire life is going to be at the moment,” said RHR. “We're on a different tire here than we were last year. It's such a small window to get the lap right; it's such a small margin for error on the current spec tire we're on, it's just crucial to try and get it right.
“And in addition to that, qualifying is so important here, but at the moment, you have to guess where your setup is going to be on Reds without actually running on them before qualifying. It's a case of making an educated guess at this point. Who knows where we'll be.”
RHR dominated the Barber race in April, taking pole position, leading the most laps and winning the race on the Barber-spec Firestones, but pointed to the difference in track surfaces as the primary reason for the struggles that have engineers searching for solutions that might not exist.
“We were just talking about how different it's been with the same exact tire we won on,” he continued. “It's pretty simple: Barber has a more abrasive surface. They ground the track down this year, so that's what made the difference, but Sonoma has stayed the same. It's almost like a smooth garage [floor] surface. It's difficult to get the right setup going, but when we do get the setup right, we'll need to get the [qualifying] lap done in one or two laps, or else the tires are falling down from there.”
Target Chip Ganassi Racing's Scott Dixon was fastest on Friday, lapping more than a quarter-second faster than Helio Castroneves in second, and noted the changing grip levels between practice sessions and the knife-edge precision required to produce a quick lap on Blacks as the biggest takeaways.
“As the track rubbers in more, the longevity gets better,” said the Kiwi, who sits 31-points behind Castroneves in the championship standings. “When the track was green this morning, I got two or three laps out of the tires before they went off, and it was a little bit better this afternoon when there was more rubber down, but not by a lot. It puts a lot of emphasis on a couple of laps – you want to be aggressive, but not overly aggressive because you can't afford to mess up and expect to have more laps with good grip to make up for any mistakes. It really makes you work hard to be very precise because you don't have the tire life to recover otherwise.
“And then the afternoon session was kind of bizarre. If you look at the top-5, there were big chunks of time between everybody, then from sixth to 10th, everybody was within one-tenth. It seemed like people were still learning a lot about the tires and maybe that's why there wasn't the same tight group of times we normally see. Nobody has a handle on what's really going on at the moment, honestly.”
Dixon is pinning his hopes Firestone's Reds becoming the tire of choice this weekend, but he and the other drivers won't know how well they'll hold up until qualifying is over.
“It will be interesting for the race!” he exclaimed. “We know where the Blacks are at, but we don't know about the Reds. It could be – I hope it is – a situation where the Reds actually last longer than the Blacks. That's happened before, and if that's the case, you'll see everybody using the Reds for as long as possible and getting the Blacks on and off as quick as they can. This track, out of all of them, needs a huge spread in tire [life] because it's so hard to pass. That's what you hope happens. If they both fall off that cliff at the same rate, I'm not sure what you'll do.”