How to Make Grippier Racetracks Using Spy Technology

If PJ1 TrackBite isn’t the Solution, What is?

Dale Earnhardt, Jr. suggested tracks stop using PJ1 Trackbite because it didn’t work well in Charlotte last weekend. He called for additional research to understand how the substance affects the track before continuing to use it. A couple of drivers expressed similar thoughts that the PJ1 actually made the race worse. Before getting into what else we might try, let’s examine whether PJ1 TrackBite failed last weekend

Reminder: How Tracks Get Grip

Grip is another name for the friction between the track and the tires. There are two kinds of friction. You learned about the first kind in school, probably by running a piece of sandpaper over a wood block. The second is the interesting kind: adhesive friction, which I think about like if you step on a piece of gun on the sidewalk on a warm day. The gum tries to hold you to the sidewalk. Adhesive friction is provided by the rubber that comes off the tires and sticks on the track.

I wrote an entire blog about how a track gets rubbered up. There’s a misconception that a green track rubbers up and then, when it reaches some optimal rubber-level, it stops.

This is wrong. Rubbering up a track is a dynamic process. Rubber is constantly being laid down while other rubber already on the track is coming up. Rubber tends to come up faster when you have cautions and the the tires cool down. I’ve taken the diagram below from a previous blog to illustrate. This cycle happens continuously throughout a race. The rates at which rubber comes up and goes down depend on a lot of factors, like the track roughness, the track surface material, and the temperatures of the tires and the track.

Review: How PJ1 TrackBite Works

To understand the disadvantages of PJ1 TrackBite, you have to understand how it works. I did a whole blog on that, but here are the high points:

  • PJ1 TrackBite isn’t a magically sticky substance that sticks the cars to the track better. It increases grip because it promotes adhesion between rubber and the track surface.
  • PJ1 TrackBite works differently on different surfaces at different times
    • Just because it works in one place doesn’t mean it’ll work in another
    • How well it works depends on everything from temperature to surface roughness to track material
  • PJ1 TrackBite is water resistant, so it stays put in rain; however, it’s soluble in oil-based fluids like, well, oil.
    • Any time a car puts an oily fluid on the track, it will have a negative effect on the PJ1.
    • The size of the effect is determined by how much fluid goes down and how long it’s in contact with the track.
  • Pj1 must be applied to the track using very specific application methods that are detailed down to the size of sprayer nozzle.

Why There Were Problems at Charlotte

The problem at Charlotte was not that PJ1 Trackbite didn’t work: The problem was how the Trackbite was applied. You have to spray the material onto the track. It goes down clear, so you can’t immediately see if there’s a problem.

Apparently, a nozzle on the sprayer clogged. The liquid was applied unevenly and not at the recommended coverage. Then there was rain and not enough time to re-apply it. A confluence of things results in the problem. Blaming TrackBite is like me blaming a sunscreen manufacturer for getting sunburned if I applied it incorrectly. This is user error, not product error. It’s going to happen, especially with a new procedure.

There’s no way to guarantee that Trackbite is going to “work” every single time it’s used. There are simply too many variables: temperature, track surface, application, accidents… If we stop using TrackBite, we stop getting data points on how it works. The experience so far is that it seems to help more times than it hurt. So I wouldn’t suggest getting rid of it.

But I also would suggest relying on it to solve all our problems.

How Do We Make Grippier Tracks?

We can think about changes in two primary areas:

  • The original asphalt laid down for the tracks
  • Coatings and treatments, which could be temporary or permanent.

Asphalt Research and Motorsports

There are people who spend their entire lives studying asphalt: how to make it, how to apply it, how to care for it, how to make it last longer, how to remove it, how to recycle it… and a ton of other areas that you probably wouldn’t think of as scientific research.

A search of Google Scholar (which indexes scientific articles and patents), yields almost a million citations. (There are 4.8 million citations if you just search Google proper.) There is a National Center for Asphalt Technology, headquartered at Auburn University. They have a test track (shown below) with 200-foot test sections they use to study different types of asphalt and treatments.

If you go to the NASCAR Hall of Fame (and you should), you can get an idea of how different the asphalt just at NASCAR tracks. You’ll find different sizes and types of aggregate, different types of binders, different proportions of binder to aggregate and more. And that’s not even considering concrete, which remains a viable material for many tracks, but requires much more energy to make and is harder to maintain.

NASCAR shares the same problem as NASA and the military: We have very specific, often extreme, requirements and they’re not shared by a lot of other people. We have higher forces, faster speeds and more heat. A lot of the research being done won’t be applicable to NASCAR. (Side note: This is the same problem motorsports safety researchers have.) State and Federal governments fund most asphalt and road research. They’re concerned with cars and trucks going 0 – 80 mph on expressways, not racecars going 200 mph on high-banked racetracks.

Some very interesting new types of asphalt are being developed: asphalt mixes that don’t wear as quickly, that use synthetic aggregate or recycled components instead of rock, that incorporate polymers in the binder to hold together better and make repairs easier, or that don’t lose grip in the rain. The problem is that these are very new developments and are just now moving from being tested at research facilities to being used on highways. Wholesale repaving of a racetrack is already risky: it would be even riskier (and more expensive) if an enterprising track owner switched to a new, mostly unproven asphalt type.

Upping the Friction

I’m using “treatments” to mean materials you apply for a specific race, like PJ1 TrackBite. PJ1 TrackBite is widely used in drag racing, so it’s a natural option for NASCAR tracks to try. There is also a history of drag racers lighting the PJ1 TrackBite on fire, which helps the compound spread out and dry more quickly. This is both dangerous and not recommended by the manufacturer.

You’ve heard the saying that 20% of the people cause 80% of the problems? Highways are the same: 23% of fatal crashes in 2015 happened on flat curves, but flat curves only make up 5% of the highway system.

States have used techniques like microsurfacing, diamond grinding, and cutting grooves into the asphalt to increase firction, but several High Friction Surface Treatments (HFSts) are now available. HFSTs are very small (3-4 millimeters, or about a tenth of an inch) pieces of a hard material suspended in a polymer binder and sprayed onto the road surface. The rock used is typically calcined bauxite, but flint, granite and steel slag have also been used. These materials aren’t as readily polished The result is better friction during wet conditions and higher friction in locations that tend to have a lot of accidents.

(Sidenote: The binder comes in different colors. Some places use the HFST to not only increase friction, but to give drivers a visual reminder that they’re entering a section of road where they might want to be just a little more careful – like a railroad crossing.

I’m not talking here about temporary fixes, like PJ1 TrackBite. I’m talking ways you could modify a track to make it grippier. (I already wrote about one way you might use a surface coating to make track drying faster!)

Lowering the Track Temperature

Tracks are grippier within a certain temperature range. The air temperature and amount of Sun on the track can vary the track temperature by a huge amount. So might it be possible to increase grip by lowering track temperature?

How do you cool 2.5 miles of track?

You can imagine a system that circulates chilled water or liquid nitrogen underneath the track surface. That would be expensive to install and a nightmare to maintain.

But it turns out (lucky for us), a lot of other people are interested in reducing asphalt temperature.

Urban Heat Islands

Roads make up about 1/3 of all surfaces in a major city. These surfaces absorb heat and then re-radiate it. There is so much asphalt (and similar materials) on roads and roofs in densely populated areas that the absorption and re-radiation of heat makes the urban area much warmer than the surrounding areas that have trees and other foilage. The effect is even more pronounced at night, which means the city doesn’t cool down as much.

These areas are called Urban Heat Islands. They’ve gotten more pronounced as we’ve made our cities bigger, crammed in bigger buildings and eliminated green spaces. This graph shows the temperatures in Tokyo (the yellow line) relative to surrounding areas. In 1907, Tokyo’s mean temperature was in the middle of the others. As Tokyo got more and more built out, it got warmer.

In addition to increasing temperature, there are other impacts:

  • more heat-related illnesses and deaths
  • the rainfall downwind of cities
  • more smog
  • higher air-conditioning bills
  • changes animal behavior and survival
  • more greenhouse gas emissions

These effects mean there are a lot of people looking into ways to keep asphalt from heating. Their discoveries could be interesting (and useful) for motorsports.

Track Color Matters!

If you have kids (or are, like me, easily amused) try this experiment: Leave a piece of white construction paper and piece of black construction paper out in the Sun for a couple hours. Come back and put your hand on each. The black construction paper will be much warmer than the white one.

If you’re really fancy, you can design a pattern with different colors on your computer and print it out. Something like this:

And put it in the Sun.

My last blog looked at how NASCAR is using thermal imaging and had a lot of cool false-color images. Here’s another one; this time, it’s a movie. It’s the pattern above, left in the Sun and imaged with a thermal camera. Red is the hottest temperature, yellow is medium and blue is the coolest. Not that the temperatures they’re using are Celsius. 15° Celsius is about 60°F. 50° Celsius is 122°F

Which color heated up the most? Black.

What color is asphalt? Black. In fact asphalt is about the worst surface for light/heat reflectance, as the graph below shows. All of these numbers are ranges: the front bar is the minimum and the rear bar is the maximum. I’ve coded the track surfaces in blue and the organic surfaces in orange.

The solution is obviously white asphalt!

As is always the case with the obvious solution, there are a couple of problems

  • There are 4.12 million miles of roadway in the United States (according to the Federal Highway Administration) It would be prohibitively expensive to replace it all.
  • There’s no such thing as white asphalt. The binder is made from the last dregs of the oil refining process. It’s black. You’re not going to make it green, much less white.

How to Make Asphalt Cool

Luckily, all the worry about urban heat islands has prompted researchers to look into ways to treat existing roads to make them less absorptive. A number of companies have developed ‘cool pavement’ materials. “Cool” meaning temperature, not hipness.

The first major test of one of those materials has just begun in Los Angeles, a city that could certainly benefit from less smog. The scientific journal Science called it “a hellscape”. The Washington Post called it “the poster child of the heat island effect“. Temperatures have gotten much warmer in LA and a lot of places don’t have air conditioning. LA is one of the few places that have heat-related fatalities in the winter.


LA is putting a reflective coating called CoolSeal down on 14 test streets. It’s a sealer, used the same way you’d routinely seal your driveway or the city would seal the streets.

How’s it Work?

The headline in the Washington Post story says it all: Why L.A. is coating its streets with material that hides planes from spy satellites.

GuardTop, the company that makes CoolSeal, started working with the defense industry years ago to make a material for airplane taxiways that couldn’t be picked up on the infrared cameras on spy satellites. Color isn’t the only factor that determines how much heat a surface absorbs: a shiny surface reflects better than a matte surface. As is usual for an engineering problem, the challenge was finding a material that reflected heat, but could still withstand the forces of a plane landing. The photo below shows infrared pictures of a coated asphalt area compared to the uncoated area. In their color code, yellow is the hottest, orange is in the middle and purple is the coolest.

CoolSeal is unique because it’s an asphalt-based product. Most of the other coatings are polymer based. I haven’t been able to find documentation to prove this, but I suspect a polymer-based product would be more susceptible to heat and wouldn’t be able to stand up to forces as well as an asphalt-based product. The reports you’ll find on CoolSeal say that it’s a white coating, but it’s actually a light grey. It’s applied the same way you’d apply most surface coatings for asphalt.

The initial tests show that the temperature of the coated area was anywhere from 10 °F to 20 °F cooler than the asphalt surface was. A number of Los Angeles reporters ran their own tests.

  • Dogs that have learned not to walk across the asphalt had no problem walking across the CoolSeal-coated street
  • People have noticed that the sealed street feels cooler.
  • Fox 11’s reporter did try to fry an egg on the asphalt and on the CoolSeal surface. It didn’t really cook on either surface, but it started to coagulate on the asphalt and didn’t change on the sealed surface.

Would It Work for NASCAR?

  • If GuardTop’s coating bears the forces of a plane landing (high speed and higher weight than a racecar), I would expect it would be able to handle forty racecars for a couple hours. When I first read about the polymer-based coatings, I worried about durability and if the coating would wear off. But it seems that, for this application, it should work.
  • GuardTop costs between $25,000 and $40,000 a mile. Before you write it off because of cost, consider the following:
    • A typical sealer runs between $15,000 and $30,000 a mile
    • The pavement will cool down the entire racetrack area, which would make it cooler for the people working and watching
    • Because the pavement is more reflective, you need less lighting, which could save money on electricity and maintainance costs.
  • It could be tried out and, if it didn’t work, a traditional sealer could be applied over it.
  • It would require a lot of work from the folks at Goodyear – but because this type of coating is likely to become more widely used, they’re going to have to start getting familiar with it anyway. Remember that grip is the tire and the track. They have to work together.
  • They’d have to consider whether the reflectivity of the surface causes issues for the drivers, especially at night races.

Conclusion: It’s a major investment of money and time, but worth investigating.

Other Uses in NASCAR?

  • If I were a driver, I would agitate like crazy for a white (or silver) interior. I feel really sorry for the drivers in black firesuits and black-interior cars. I’d inundate my owner and crew chief (and sponsor) with all the literature showing that an overheated driver is more likely to make bad decisions.
  • Here’s an idea for NBC Sports: Put thermometers in a car with a white interior and in a car with a black interior and check in with them over the course of the race. That would be a great science experiment teachers could use for their classes and so much more interesting than two sheets of construction paper.
  • Track owners who have seats painted dark blue or dark red might want to re-think their color scheme just to make their patrons more comfortable. Then again, a cool beer could accomplish the same purpose.

It Works for your House, Too!

I was going through my reading feeds and found this article about how thermal reflective paint can help cool your house, too.

ADDED: 4:49 10/13/17: Just found this article about a paint that actually cools when it’s exposed to sunlight. It basically absorbs heat and re-emits it as light (the basic principle of laser cooling.)

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The Physics of NASCAR is 15 years old. One component in getting a book deal is a healthy subscriber list. I promise not to send more than two emails per month and will never sell your information to anyone.

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