JEC_31

In the "Racecar Tech" section of the RX-7 Forum, a great debate rages. An experienced FD (the last generation twin-turbo RX-7) autocrosser and track-day'er named Damon posted that "The classic racing line is sooooo slow..." based on an article in Racecar Engineering:

http://www.rx7club.com/showthread.php?t=330669

What do you Shark racers think? What works for you?

Jim_H

Interesting. HP would play a big part, as they are discussing. After sitting at PIR yesterday at turns 1 & 2 the interesting thing to see was there was no one line that all cars used. This was the LeMans so I got to see a # of different cars using different lines. I think for people who only track 1 or 2 times a year the classic line is the one to use but will be interested to see what the week end warriors have to say.

Dennis K

Racecar Engineering has been running a series of articles about this over the last few months. They usually have feature articles like this when a manufacturer is introducing some new product.

Mitchell Software page

NASCAR guys do this all the time. If you've seen the race at Bristol or Darlington, it's pretty obvious that they follow that parabolic line. I see the CART guys doing it at Turn 2 at Laguna Seca too.

As a casual open track day guy, I've found trailbraking on the limit is a tough thing to do consistently. It's an advanced skill and I'm still trying to learn the basic ones.

Bill Ball

This debate has raged on in the motorcycle world for a long time too, although even more away from the classic line. Reg Pridmore won a lot of races by hugging the inside of the track. No wide swings out to line up for an apex. His son has continued the tradition.

http://www.classrides.com/roadwrk.html

Realist D.

It’s impossible to make a statement like that and expect it to be relevant to a wide variety of 180 degree corners and a wide variety of cars. For example, the parabolic line they describe would in fact be fastest for a car with outstanding brakes and outstanding acceleration since it places most of the emphasis for the corner on braking into and accelerating out of the corner (rather than zooming through the apex at max speed). But if a car is weak on brakes, or can easily overheat the brakes, or is weak on acceleration, then the classic line that maximizes momentum would be fastest.

For a “momentum” race car like a Formula Vee, the classic line would be fastest since those cars don’t brake or accelerate with much authority. Also, most street cars being driven at track days should go fastest using the classic line.

Motorcycles are a different story altogether. With bikes it’s a trade-off as well though. Race bikes don’t provide much absolute cornering G’s but they can brake and accelerate better than most race cars. So a race bike would benefit most from a parabolic line except for the fact that they don’t respond very well to mid-corner line changes. A race bike with a lot of power can be muscled into a mid-corner line change by sliding the rear wheel, so you will notice that Superbike riders often cut a parabolic line through a 180 degree corner, while a “momentum” bike like a 125GP (which I have 1000’s of laps on) will go best when maximizing momentum and cornering speed (use the classic line).

There’s another thing to consider in this argument, and that is race-craft. Using the classic racing line on a 180 degree corner leaves you wide open to an inside pass done by a competitor following you, even if this classic line is faster for your vehicle. He can cut down the inside leaving his braking later than you, and then block your path to the apex. If you want to defend the corner in this situation you pretty much have to take a parabolic line and leave your braking as late as possible.

And there's still one more thing to consider, and that is the condition of the track surface on a particular corner. I've been on some tracks where the braking zone for a particular line into a corner is severely rutted (like what you find approaching a stop sign on a dirt road), so you may need to find some other line through the corner to get your best lap time. The track surface at the apex can also become rutted the same way, which may force you to move your apex earlier or later, or further out from the inside of the corner.

So, you can see that making a finite statement like the one at the center of this controversy is pure folly.