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.
Track Taxonomy
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.
Banking
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.
Backstretch Lengths
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.
Speeds
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.
Pole speed depends on corner banking, which makes sense. Banking helps the cars turn by providing some of the required centripetal force. More banking means more speed.
There is still, however, a 4.2 mph difference on the three quad-oval tracks. That means we must consider factors beyond shape.
Track Surfaces
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.
The Similarities
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.
The Conclusion
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.
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Note: I refreshed this post on 2021-03-21 to update the graphics and clean up/shorten the text.
I’m a software engineer and a huge Nascar fan. Anytime you can use the word taxonomy in reference to Nascar is a good day! Thanks so much for this article and your other content as well. I approach racing from an engineer’s perspective and your articles never let me down. Keep up the good work! Also, thanks for doing the tires article. Awesome!
Gary – thanks so much! More coming on tires. Tires are fascinating. Fifteen years teaching physics and I had no idea that you could have a coefficient of friction greater than one until I met tire engineers!
Hi there. Big fan of your site; it’s interesting to see a scientific take on Nascar. Based on your evaluation above (which left out Michigan & California in my opinion, but you covered the meat of the issue) you say it’s the car, not the track that is contributing to the parade racing at these tracks. What can be done to the cars, in your opinion, to make the racing better at these tracks?
Thanks!!
Michael: I was focusing on 1.5-mile tracks. Michigan and California are 2 mile tracks. NASCAR classifies them as superspeedways, although they don’t really go in the Dayton/Talladega mold. They’re both moderate banking and D-shaped ovals. In my opinion, here’s the issue: cars are very dependent on aero for downforce. When one car gets behind another, the trailing car loses downforce while the lead car doesn’t (or doesn’t lose as much). This makes it hard to pass. If you decreased the ratio of aerodynamic downforce to mechanical downforce, I think that would help — however, it would also take the speeds down quite a bit. That may be a naive approach, but I think that’s where they have to start. Problem is, it’s a touch problem to change and takes a lot of research – which means a lot of time. I suspect, however, that it might be a bit cheaper than repaving a track! Thanks for reading!
I doubt that most fans would dispute that each of these tracks has some differences individually. What they do tend to have in common, in spite of their differences, is that the races as most of these tracks tend to play out the same way. Long green flag runs, little passing on track as opposed to during green flag pit stops, and cars strung out over then entire track. Most of them do not make for compelling races, and tend to be deadly on TV.
Thanks Diandra!
Excellent article!! No track is the same, besides visibly! Cant wait to see what you dig up on these tires.
I honestly believe the parade racing as you call it, is a resultant of the aerodynamic parity, between the different manufactures, following the introduction of the COT. Before COT, the twisted sister cars, all had differing templates specific to the brand. My belief, next year with new cars with more shapes and angles, meaning more “gray-area” for teams to work with, think C-pillar fiasco, will result in more passing. Not totally erasing the issue, as some teams are just simply better funded than others. But, Also, the difficulty passing is a result of these cars being “stock cars,” they are supposed to be equal, and races today show it tremendously that the aerodynamics are fairly even across the board, when you hear every driver say its hard to pass, or that track position is key. Whats their excuse later in the run, that they cant catch the car several seconds in front of them, if the air is mostly clean?
I don’t believe its completely the dirty/turbulent air, as they make it seem, because in the middle of fuel run, lap times are very comparable, and the cars are spaced out around the track. I believe it boils down to the total package, tires, chassis setup, driver input and aerodynamics, being even. Heck Gordon came from 34th to 4th, he surely didn’t seem to mind the wind or the dirty air last Saturday, while conversely he practiced and qualified miserably, mostly on a track with clean air ahead, suggesting his car works better in this dirty race air, at least to me.
If we allow air to travel under the car, like back when the cars were their factory twins, the dependancy on aero would be reduced, and with aero grip reduced, drivers would have to work the throttle and actually “drive” thw cars, what an interesting concept…jmo
Very good article however I think you are missing a key piece of information, and that’s the transitions from the corners to the straightaways and vice versa. Those transitions are the difference between Charlotte and Texas. At Texas the corners and the straightaways are at relatively the same elevation (just eyeballing it). So the transitions are very flat at Texas, where as at Charlotte the turns seem to be higher than the straightaways, so the banking doesn’t flatten out on corner exit like it does at Texas. I feel like this is a key piece of information that further differentiates the 1.5 miler’s.
Harrison: You are 100% right. That was a key piece of my discussion of this on SiriusXMSpeedway last Friday and I totally forgot to put it in the blog article! Thanks for bringing this up – it is indeed a major difference in the track layout. I was trying to get some data to quantify this, but I’ve not been able to do so yet.
Interesting article, Diandra and a great explanation of the “differences” in the tracks. The problem continues to be, however, that regardless of their physical differences, when the race itself isn’t interesting (similar to Sal’s point), it essentially isn’t interesting to watch.
Always enjoy your fact-based, scientific reports Diandra. The problem with these tracks is that you end up watching an Aero-push 500. I remember in the 80’s when the cars more resembled stock cars, certain manufacturers would complain to NASCAR that they didn’t have the same downforce as the others. So, NASCAR would let them extend the front air downs another inch or so. And, after a while, another manufacturer would complain about a disadvantage and the front air dams for their cars would grow. And so would the dependency on “clean air”.
I wish NASCAR had gone the opposite direction and took away some of the air dam size from the faster models. They need to get back to more mechanical grip and less aerodynamic downforce. And the sudden building of a bunch of high speed, mile-and-a-half tracks several years ago displacing the smaller, slower tracks on the schedule just made the problem more of a weekly headache for the hapless fan.
Yes, NASCAR now has lots of fast tracks with huge grandstands by big cities but they also killed the racing.
Nice analysis…but the racing at the cookie cutters is still boring (as is Michigan & California).Real racing can only be seen at Rockingham, North Wilkesboro, & Darlington. All of whom were sacrified for ‘markets’.
I agree with you, Mike. My point (which I may not have made straightforwardly enough) is that the racing we see isn’t just because the tracks are the same. It is because all of these tracks share certain characteristics that, coupled with the current car and the current tires, produce the racing we see. While I certainly wouldn’t mind turning some of the 1.5 mile tracks into close cousins of Rockingham and Darlington, that realistically isn’t going to happen. So the question we’re left with is: what can we do with the tracks we have to change the style of racing into something more like what we see at those much-loved (and much-missed) tracks? Every answer I can think of would result in slower speeds; however, the comments I get sound to me like many people would willingly sacrifice a little bit of speed for more competitive racing. Thanks for your comment!
The person that said “let the air go UNDER the car” has the right idea. Ever since the went to the soft spring-bug bar setups the nose of the car is on the track making it more aero dependent.
Thank you so much for this article. You explained tracks, how all the details effect it & how they wear over time. And the fact they aren’t even identical cookie cutter tracks in reality – so even I got it. Keep up the excellent work!
Diana, I have a question. Why doesn’t NASCAR try to mandate suspension geometry rules that would make it impossible to get the splitter/airdam no closer to the ground than say four or five inches? Is it not possible? I ask because In the 80s and 90s, when teams hadn’t yet figured out ways to coilbind and seal off the front end, we saw the cars run Charlotte, Atlanta, etc. with a lot of ground clearance even under maximum cornering load and the racing was much closer, and by closer, I don’t mean statistically closer like they keep claiming today’s racing as being but that cars could actually race much close to each other during a battle.
Now even though the aero plays a big role in these races, they will always be relatively boring because certain cars will have a better mechanical package, and will be faster. The only thing that would be different without aero is that these faster cars wouldn’t get stuck behind slower cars as they made their way through the field.