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What matters at Michigan: With clean air comes control of the race

A.J. Allmendinger joined the Motormouths crew to talk about his win at the historic Brickyard and the winding path he took to get to his second NASCAR Cup Series win.

What matters in today’s NASCAR Cup Series race and how important is clean air? Let’s dive into the analytics and trends shaping the FireKeepers Casino 400 (3 p.m. ET on NBCSN).

Michigan’s clean air is an advantage, but a lack of falloff on worn tires keeps leaders honest

Kevin Harvick, bestowed the fastest car for both legs of a doubleheader, swept the weekend last year in Michigan. And hats off — it’s a good advantage to have, and perfect if you can replicate it.

But the problem with Harvick’s path is that of the 37 teams in today’s race, 36 won’t have the fastest car. An alternative pathway to victory is a must for the majority of the field; however, there’s one trail already forged.

It took one race for the combination of Michigan’s negligible lap-time falloff on worn tires and NASCAR’s 550-horsepower package to be capitalized upon, as Joey Logano sailed to a 2019 win in what was the fourth-fastest car in the race. Dominant by virtue of leading 80% of the contest, he utilized the longer spoiler to aero-block a pack of faster cars according to timing and scoring data, one of which belonged to Martin Truex Jr. This showcased the important advantage offered to the car with the most clean air.

“I don’t know if we could have done anything with (Logano),” Truex said after the race. “We were going to need one heck of a push from behind — a shove down the straightaway. I could get a little bit of a run but never enough to get next to him and surely not enough to get next to him and clear him getting in the corner.”

To the car with clean air goes control of the race, but retaining that control could prove difficult. The degradation in lap times across runs, if there’s any at all, allows for sizable leapfrogging via pit strategy, under both yellow and green-flag conditions. Both races in 2020 lacked green-flag pit cycles, an aid to Harvick’s victories in which vulnerable moments were removed due to the placement of caution flags. Had they occurred, his lead position would’ve firmly been in the crosshairs of those deploying calculated risks with the timing of their stops.

Still, Harvick was dealt a few other challenges, namely the debut of the choose rule on a track where the natural restart slotting wasn’t equal for all competitors. As the lead car for the majority of the weekend, he made good use of his chosen launching spots, retaining position on nine of 12 attempts, netting six positions in the process.

His performance gives credence to a focus on short and intermediate runs to establish track position which might sustain for the duration of a fuel run, unaffected laps on worn tires willing. Harvick ranked first in short-run speed in the Sunday portion of last year’s doubleheader while ranking seventh in long-run speed. It was a scenario in which track position — and the clean air it provided — masked a measurable disparity.

The restart dynamic is a deceptive curveball for competitors

Restarts on the 2-mile track look simple enough, but what’s visible is misleading. The outside groove is the strongest of the two restart lines by a hefty margin — with a difference in retention of 56 percentage points across its last four races — but that’s a common challenge in the double-file era, good enough for the existence of the choose rule.

But when you consider, a driver should prefer to start sixth rather than fourth and 12th as opposed to seventh, that’s when things appear to get a little strange. It’s a track that begs for drivers to pick their own launching spots:


Cars restarting fourth typically act as pushers for the lead car, and that’s a coupling that can drift down to the bottom groove. Those directly behind them in sixth tend to stand pat in an outside line that reliably chugs through the corners. In the last four races, sixth has averaged a better running position after two laps, 3.72 compared to fourth place’s 3.76.

Overall, the inside groove offers little daylight for its occupants, a mistake in the making for the first few front-runners. How drivers and teams game the choose zone today will impact everything that follows, to the extent that the winner will surely have been a studied chooser.

Fastest car or not, another brilliant Larson performance is in the cards

Harvick isn’t the only Michigan dominator returning to his most successful racetrack. Kyle Larson, a three-time winner at MIS when driving for Chip Ganassi Racing, will get a fair crack at winning in his first start there for Hendrick Motorsports.

That’s an evaluation that isn’t totally dependent on having the fastest car. While his 18th-place showing last month in Atlanta gave fuel to a rumor that NASCAR asked Hendrick Motorsports to make changes to the nose of its cars, it wasn’t as if Larson was slow on the 1.54-mile track, the most recently visited 550-horsepower facility.

He ranked fourth in median lap time, losing ground to winner Kurt Busch (who also had the second-fastest car in the spring race at Atlanta) and Kyle Busch, the top-ranked producer on 550-horsepower tracks with the third-fastest car on the track type across the whole of the season.

Of course, Larson would make good use of the fastest car, but speed on par with what he had in Atlanta should prove fast enough to claim clean air and keep it, based on what we’ve seen from his team’s improved performance on pit cycles.

None of Larson’s three Michigan wins came in the present-day 550-horsepower package, but he’s proved an able passer all season long on tracks utilizing the low horsepower/high downforce rules set — he ranks second in surplus passing value — and his 69.57% retention rate on restarts ranks as the fourth-best mark.