The Holy Grail of Racing: One Car for All Tracks

One car for all tracks means that a single car races competitively on everything from superspeedways to road courses. The goal is producing the best racing possible while keeping costs down.

But is it even possible to have one car for all tracks?

A Little History

When we say ‘one car’, we really mean that the most expensive parts of the car don’t change. Remember back to the early-to-mid 2000s, where teams were literally designing a different car for each track. They modified the chassis by adding wooden reinforcements in bumpers and doors for short tracks. Engineers tweaked bodies and spent hours in wind tunnels and developing computational fluid dynamics simulations to optimize body shape for each track. They clear-coated over decals on superspeedway cars so the cars could be as aerodynamically sleek as possible.

It cost a lot of money, but they didn’t really have a choice. Because everyone else was doing it, you couldn’t win if you didn’t do it, too.

The CoT was NASCAR’s first attempt at one car for all tracks. They fixed the body shape and moving all the aerodynamic adjustability to bolt-on pieces that could easily be changed: A wing and a splitter. A spoiler quickly replaced the wing, and NASCAR later changed the body to better reflect manufacturer styling.

But they still haven’t found the holy grail. Or have they?

Can they?

Experimental Variables

NASCAR has always used horsepower as a limiting variable. In addition to limiting speed, horsepower limits also cap the rpms the engine can reach. Keeping engine speed below about 10,000 rpm lets engine builders use mundane, lower-cost materials instead of more-expensive alloys. Restrictor plates (later tapered spacers) were used to limit speed even more at superspeedways.

In 2019, NASCAR turned to a second variable: downforce.

2019: Fixed Aero/High Downforce Everywhere

In 2019, NASCAR instituted a high-downforce aero package with a big spoiler and splitter, and a sleek underbody.

  • Spoiler: 8” x 61”
  • Splitter: 2” overhang, 10.5” wings at splitter ends
  • Radiator pan: 37” in front tapered to 31” with vertical fences
  • Aero ducts: Used at majority of oval tracks larger than 1 mile

While the XFINITY series had long used a tapered spacer to tailor engine power output, the tapered spacer now came to the Cup Series. The Cup Series uses two sizes of tapered spacers:

  • 750 HP: 1.17” tapered spacer (for short tracks and road courses)
  • 550 HP: 0.922” tapered spacer (for oval tracks larger than 1 mile)

That gave us fixed aero and three engine configurations: Taper550, Taper750 and Superspeedway. But the 550Taper package could be run with or without aeroducts, The teams actually had four configurations to worry about.

High downforce with aeroductsXX
High downforce without aeroductsXX

While it’s still one car, the number of configurations matters. The moneyed teams will do research and development for each configuration. The optimal setup for a Taper550 with aeroducts is different than for a Taper750 without aeroducts.

But four is still less than one for each track.

2020 Rules Package

The 2019 rules package worked well at the 1.5 mile and larger tracks, but not so well at the shorter tracks. Martinsville and Richmond, in particular, had lackluster races in 2019. Drivers and fans grumbled.

NASCAR needed more more variability. So in 2020, they introduced a second, lower-downforce aero package. This package featured smaller spoilers (2.75″) and splitters (1/4″ overhang), intended to emphasize handling and driver input. They christened this aero package ST/RC (Short Track/Road Course). It was used at tracks 1 mile and smaller, and at road courses.

The original aero package — the high-downforce package — is called “NA18D” for reasons I haven’t been able to figure out yet. If brake ducts are used instead of aeroducts, they call the package NA18D*. Again, it seems like a small change, but each variation opens the door to spending more R&D money.

Hold on — I’m not going to count configurations yet because it gets even more complicated in 2021.

2021 Rules Package

In 2021, NASCAR opted to use the low-downforce package at tracks 1.3 miles and smaller (i.e. Darlington and Nashville). Although that doesn’t increase the number of configurations, they also added a dirt track, which necessitated a Taper750* engine package.

For a full rundown of the packages for all three years, see my explainer.

Teams can run either NA18D* or ST/RC at COTA, Road America, and the road course at Indy. But you and I know that the big teams investigated both possibilities to determine which one would work better.

So even though we talk about one car for all tracks, we’re really talking about five packages. That’s R&D for five different combinations.

Of course, all of this will go out the window with the arrival of the NextGen car next year; however, NASCAR will have the same issues of having to tuning that car for all the different tracks the series visits.

Has It Worked? Do We Have One Car for All Tracks?

It’s actually hard to say because racing has so many variables. Nowhere is that better illustrated than last weekend’s races at Pocono. Doubleheaders are rare opportunities to compare because so many of the variables are, if not constant, at least comparable.

The weather was similar, the track surface didn’t undergo any massive changes, and teams didn’t have a couple months to go back and think about how to better set up their car. They used the exact same package and, in most cases, the exact same car. The race lengths differed by only ten laps.

And look how different the races were.

The Race Flow

Let’s start by looking at the Caution-O-Grams for Pocono 1 and Pocono 2. A Caution-O-Gram is my way of graphically showing the race flow.

The Caution-O-Grams for the two Pocono races show that the races flowed very differently

Race 1

  • Debris and accidents interrupted the race throughout stage 1 and stage 2.
  • We had eight cautions for a total of 25 laps.
    • Six of those laps were stage-end cautions
  • Cautions made up 22.5% of the race,
  • We had 105 laps of green-flag racing.
  • There were 8 green-flag runs
    • Only three were 19 laps or longer. (19, 24, 27 laps)
    • Three more were 9 laps long
    • The remaining three were 2, 2 and 3 laps.

Race 2

  • We had one early accident and then nothing unplanned until a debris caution early in stage three.
  • We had four cautions, two of which were stage cautions, for a total of 15 laps.
  • Cautions made up 15.6% of the race
    • Stage-end cautions were four laps long in race 2, but only three laps long in race 1
  • We were left with 125 laps of green-flag racing.
  • There were 5 green-flag runs
    • Three were 25 laps or longer (25, 44, 51 laps)
    • The other two were 2 and 3 laps.

The Players

We can use the Lead-O-GramTM to compare which drivers led laps during the weekend races.

The Lead-O-Grams for the two Pocono races show that different drivers led laps throughout the weekend.
Sections with stars indicate green-flag pit stop cycles. Slash fills are leads taken during yellow flags.

I used consistent colors for both graphs, so you can see that Larson, Logano, Chastain and Ku Busch, all of whom led laps in race 1, did not lead laps during race 2. Byron and Bowman were the only two drivers who had strong leads in both races.

Variable Alert!: The Invert

The invert was one of the big differences in variables between the two race, and you can see the effect on the Lead-O-Gram. Buescher and McDowell led laps early because of their starting positions, but weren’t factors at the end.

Blown tires and fuel strategy impacted who won these races much more than inverting the first 20 finishers from race 1 to set the starting grid for race 2. You can see that the cream rises to the top by comparing the starting and finishing positions of each driver for race 1 vs. race 2.

A scatter plot of finishing position in race 1 vs. in race 2 shows that the same cars mostly did well in both races.
Red dots indicate drivers who DNFed one of the two races.

If you look in the yellow shaded box, you can see that, out of the drivers finishing in the top 20 on Saturday, only 3 finished outside the top 20 on Sunday — and one of those was due to a DNF.

If you do the same thing for the top 10, you’ll see that only three drivers who finished in the top ten on Saturday failed to finish in the top ten on Sunday.

Does This Rules Package Work at Pocono?

Given these two very different races, how do you tell if the rules package works at Pocono? Without Kyle Larson blowing a tire on the last lap in race 1, would people have rated this race as highly as they did?

The problem is that there are so many variables affecting a race — everything from how aggressively a driver pushes his tires to a radio issues that complicate driver-crew chief communications — that you can’t necessarily tell that a particular rules package works or doesn’t work on the basis of a small number of races.

Let’s look at the number of lead changes over the years at Pocono.

A stacked column chart showing the number of lead changes at Pocono from 2000-2021. There's no big break in the years when new rules packages were announced.

The numbers have gone up and down over the years. But you don’t see a big change in this — or any other metric — between 2018 and 2019.

NASCAR’s problem is that the big thing you can tell with a new package is when it doesn’t work. It was really clear in 2019 that the high-downforce package was not working at short tracks, and NASCAR changed the package when they saw the problem. Unfortunately, these aren’t things you can necessarily predict ahead of time.

Engineering, unlike physics, is the art of making compromises. You can’t have everything you want, so NASCAR has to strike a balance. They don’t always get it on the first try.


Remember all of this when the NextGen takes the track next year. Give it the first half of the season before deciding the new package is the best thing in the world or the worst. And remember that it might take some tweaks before they get the NextGen exactly where they want it.

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