What keeps me up at night

I wasn’t always a fast driver. Getter faster took a combination of book learning, sim racing, data analysis, and self-coaching. Looking back on my driving journey, I would say that the most important reason I improved is because I had a lot of questions that needed to be answered. Exactly how does a tire compound change a lap time? Specifically what is one driver doing with the wheel that another driver is not? I went after these questions with gusto because puzzles motivate me.

I’m now at the point where many of my critical questions have been answered and my improvement as a driver has slowed.

Don’t get me wrong, the only peak of performance I’m reaching is my own. I’ll never be a pro driver. I didn’t start early enough, I don’t have the time, I probably don’t have the talent, and I definitely don’t have the money. But even as I slide into the comfort of my performance plateau, there is a burning question that keeps me up at night.

If you watch rally drivers on loose surfaces, they all drive with a lot of yaw. But on sticky surfaces they drive much tidier. Some of this is down to safety: it’s easier to make corrections (e.g. dodge sheep) mid corner if you drive a rally line. But even in arena rallycross where the cars can drive a more optimal line, they still drive with a ton of yaw.

I remember watching a video of Sebastian Loeb’s Pike’s Peak run a few years ago and noted how tidy that was. Check this out. Where are all the tank slappers?

So what precisely is my question? At what point does driving with massive yaw give way to driving without any? And by point I mean grip level, because that’s what the factor appears to be. Low grip = high yaw. High grip = low yaw. Is it as simple as 0.8G? How much does it depend on the power of the vehicle?

Testing

I’ve decided I want to test this in simulation. In order to do the proper experiment, I need to drive several different cars on some very simple tracks with varying grip levels. Where do I get such a track? I’m going to make them myself. I just purchased Race Track Builder, which is software that outputs to Assetto Corsa or rFactor 2. I’m just learning how to use that now. I have to say, it’s pretty fucking cool. In addition to making some “burning question” tracks, I want to build some rally stages using nearby locations. So yeah, it’s time to add “building racetracks” to my ever growing list of hobbies.

2 thoughts on “What keeps me up at night

  1. I seem to remember reading somewhere that the high-yaw rally driving style was due to the loose nature of the surface, rather than simply the grip level available. Supposedly the gravel (or dirt, snow, etc) moving under the sliding wheels will “pile up” and provide more grip than you would get otherwise. That suggests to me that this is not a technique that would be useful on a solid-but-low-grip surface like polished concrete.

    I don’t know if this is true, but if so then that suggests to me that the simulation may not be useful because it’s going to depend more on the way that the physics of the tire/surface interaction are simulated than on the driving techniques.

    What about wet pavement? Large amounts of yaw does not seem to be the “fast” way to drive in the rain — yes you do tend to see a lot of sliding in wet races, but I think that’s more due to the unpredictable nature of the grip level than intentional high-yaw techniques.

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    1. I had the same thoughts. AC doesn’t have a proper model for dirt. If a rally line in AC is faster at low grip levels, it will show that it’s really not about the dirt. However, if it’s slower, there isn’t much I can say.

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