Fans tend to lump all 1.5-mile tracks into the ‘cookie cutter’ bin. Crew chiefs don’t — because each one has unique challenges.
The accusation directed at the one-and-a-half mile tracks is that they are so identical you can’t tell one from the other. But are they really identical? Armed with Google Maps, data from racing-reference.info, and the Excel file in which I’ve collected track parameters), I dug in to see how similar these tracks really are.
A Taxonomy is simply a way to classify things, like animal species or plants… or race tracks. We start at the top with 1.5-mile tracks. The first distinction is the track shape because not all ovals are equal. Homestead actually is oval shaped.
The other tracks have one of two shapes: D-shaped or quad-oval. Atlanta, Charlotte and Texas fall in the latter category, Chicagoland, Kansas, Kentucky and Las Vegas are in the D-shaped oval Camp. The difference is evident in the figure below. The photo in the upper left is Kansas and in the lower right is Atlanta. The D-shaped oval is more of a triangle while the quad-oval has a double dogleg. The D-shaped oval looks like someone grabbed the long side with two hands and pulled. Intermediate tracks don’t have a monopoly on D-shapes. California, Michigan and Richmond are D-shaped ovals, too.
The second distinction between cookie-cutter ovals is banking. Within the D-shaped ovals, no two tracks have the same corner banking. Kentucky is 14°, Kansas is 15°, and Chicagoland is 18°. Las Vegas has progressive banking that runs up to 20°. (Homestead also has progressive banking.) The quad-ovals all have the same corner banking (24°), so we can’t differentiate that class any further in this level.
To distinguish between quad-oval tracks, we have to look at things like the backstretch length. Charlotte and Texas have approximately the same backstretch length (~1350 ft), while Atlanta has an 1800 ft. backstretch. Although Charlotte and Texas have similar frontstretch lengths, they do differ by 300 feet, so if you were really looking for an excuse to put them in separate categories, that’s about the most obvious division.
Next, let’s look at how the tracks race. Pole speeds on so-called ‘cookie-cutter’ tracks vary from an average of 174.8 mph to 193.0 mph.
There is still, however, a 4.2 mph difference on the three quad-oval tracks. That means we must consider factors beyond shape.
Asphalt is a much more complex material than more people give it credit for being.
Asphalt is a composite of aggregate (stones) and binder (bitumen). The aggregate size distribution, the asphalt’s chemical makeup and the way the asphalt is deposited impact racing, but also how the track wears. Weathering changes the track surface, and no two tracks experience the same combination of factors.
The diagram above shows how the aggregate (grey) and asphalt (black) wear over time. More of the aggregate is exposed with time and sharp edges round. Tracks also change in response to temperature and, again, different tracks change in different ways. Atlanta, for example, is a tire-eating track because its rough surface is very hard on rubber.
The same issue arises over the course of a single race. When you hear a driver or crew chief talk about “chasing the race track”, it means that the setup they had that worked so well at the start of the race didn’t work as well during the race. A track changes significantly over the course of a race: it heats up due to friction between tires and the track, plus it may heat or cool due to the way the Sun hits the track (or portions of the track) or even just because a race goes into evening and the overall temperature changes. Different weather means different racing.
Bumps Further Distinguish Cookie-Cutter Tracks
In addition to the small-scale roughness discussed above, some tracks have larger perturbations in their surfaces. Texas has a major bump between Turns 1 and 2 that was caused by the track settling over the infield entrance. In 2007, they drilled a bunch of holes in the area and injected a structural urethane to try to fix the giant distraction. They made it better, but you have still heard drivers all week talking about “the bump”.
This isn’t unique to Texas: Charlotte has a big bump entering Turn 1. Those bumps pose major challenges for setting up the suspension. The ideal position for the splitter is as close to the track as possible – but if there’s a big bump, you have to make sure that the splitter doesn’t hit the bump. There are also issues like seams and patches, where the texture or type of asphalt changes, that challenge drivers.
This is not to say that these tracks don’t share some similarities. They are all fairly wide (50-60 feet) compared to smaller tracks. The most important similarity is less a function of the track and more a function of the car. The current version of the NASCAR stockcar is highly aerodependent on one-and-a-half-mile tracks. Aerodynamic forces go like the speed squared, so these high-speed tracks have three-to-four times more emphasis on aero than short tracks.
A car depends on air rushing over it to push its tires into the track. Turbulent air – like you find in the wake of a high-speed car – doesn’t provide as much downforce as laminar (straight-flowing) air. This is why drivers value “clean air”. If you’re the first car in line, you don’t have turbulent air from the car in front of you because there is no car in front of you. Another feature of 1.5-mile tracks is that, because it is larger, you don’t run up on lap traffic as much as you do at a short track, and there’s plenty of room for a lapped car to get out of the way. At these tracks, being out front gives you have a huge advantage. That leads to a car that can easily put quite a distance between itself and the rest of the field.
The ‘aeropush’ effect happens when you get too close to the car in front of you. The air coming off its rear end is turbulent and doesn’t give you as much downforce as laminar flow would provide. It’s like running over ice: the only thing you can do is slow down. The aero-push makes it really hard to pass because you have to get close to the car in front of you in order to pass it. If the cars weren’t so dependent on aerodynamic downforce, then losing a fraction of that downforce wouldn’t affect them a significantly.
I’d say there are actually only three ‘cookie cutter’ tracks: Texas and Charlotte are identical twins that get their hair cut differently and refuse to wear identical clothing. Atlanta is a fraternal twin to Texas and Charlotte. Lumping the D-Shaped Ovals in with these tracks, however, is unfair. The issues that many race fans have with racing at these tracks requires changing the car rather than changing the track.
Note: I refreshed this post on 2021-03-21 to update the graphics and clean up/shorten the text.