Course Dependency vs. Driving Lines

I was at an autocross event this past weekend with a relatively small group I run with only two or three times a year. On my last run the starter (who I didn’t know) leaned into my car and remarked something about how I show up in different cars but I’m always fast.

It may be true that I’ve raced in three different cars (not all mine) in my last three visits.

Still, I had to think about what he said because I wasn’t sure why he thought that would be in any way remarkable. I mean, ok, thanks for the complement!, but if you know how to be fast why should the car matter too much? Of course, it takes me a while to get the hang of any particular car and I don’t have nearly the multi-car experience like some of my car-slut friends.

I think we need to make the following distinction:

Course dependency between cars is a real thing. One car can be highly favored over another because of course differences. This is mostly influenced by power-to-weight ratio which varies widely between classes and preparation levels and to a lesser extent is influenced by car width and transient response. On the other hand, cornering and braking performance is very similar for all cars on Street tires and all cars on race compound tires, respectively.

But driving line differences between cars, while real, are relatively smaller than course dependency. The principles that produce speed on the autocross course are constant and apply quite generally to all cars and all classes.

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