Forum : Solo Lines

Location, Location, Location

Autocrossers, this article is about picking your racing “line,” the path you are going to try to follow around the course.  Some courses offer few choices of line; but if you go to a National Championship, National Tour, or Pro Solo, or if your local course designers try to give you comparable challenges, you are going to see courses with enough width and depth to give you many opportunities to miss the line and lose lots of time.  If you can learn to analyze the course for a good or “correct” line, you may lop whole seconds off your run times.

How can I make such a bold statement, “whole seconds”?  Consider the possibility that “on line” through a turn might be one tenth of a second quicker than “off line.”  Possible?  Probable!  Consider also that a past National Championship course had 19 turns. That’s 1.9 seconds behind for the driver off line. Add the slalom cuts on that course, and there were 23 turns. Anyone overcharging a slalom turned slalom “cuts” into “whole turns.” That driver is at least 23 tenths or 2.3 seconds behind.

So, is line important? I think line is critical.

How do we find or figure out the right line?  My first advice is to read a book.  I got exceptional basic training in line analysis from one chapter of an old but excellent book about road racing called Driving in Competition by Alan Johnson.

Mr. Johnson defined three types of turns and labeled them Type 1, Type 2, and Type 3. (Rocket Science!)  Type 1 is a turn before a straight.  Type 2 is a turn at the end of a straight.  Type 3 is a turn between turns.  In his autocross book, Dick Turner called these “egress,” “ingress,” and “neutral.”  I like 1, 2, 3.

Type 1 turns are the most important, and the single most important turn on a course is the turn before the longest straight.  If we do these turns right, we get to full throttle sooner, we get onto the straight with higher speed, and we carry the higher speed the whole length of the straight.  Type 1′s are always “late apex” turns.  The apex is the point at which the tires are the closest to the inside edge of the turn.  The apex for a Type 1 turn is usually about two-thirds around the arc of the turn.  To set the car up to take the late apex, we must give up speed in the early part of the turn (remember “Slow Down to Go Fast”?).  This allows us to go to full throttle, and actually start the straight, prior to or at the apex of the turn rather than after the apex or part way down the straight.  We are, in effect, increasing the length of the straight.

Type 2′s at the end of the straight are often early apex turns.  The earlier apex allows us to stay on the throttle longer and carry speed deeper into the turn.  But analyze carefully because the turn at the end of the straight may also be a turn at the beginning of the next straight, a Type 1 in disguise.  Although Type 3′s, turns between turns, are less important than 1′s and 2′s on a road course, they may be all important if the autocross course is all turns, therefore all Type 3′s.  Apexes will often be at or near the middle of the turn.  We want to motor through the 3′s with speed but also with care.  If we start sliding around, we start losing time.  Consider the purist combination of Type 3′s, the slalom.  Slaloms give us excellent opportunities to add several seconds to our times.

You may have heard the term “economy of line.” To me this means that it is not always necessary to drive way to the outside of the course, then way back to the inside to catch an apex, then way back to the outside to “use all the course.”  Some course designs give us lots of room just to draw us into wasting time driving out into the open space. A much tighter line may be the time saver.

Now here is my freehand formula shoebox racer to demonstrate some turns:

Line analysis requires more discussion and study than I can put into one article. We didn’t even get to that infamous killer of F Stock cars, the dreaded decreasing radius turn (which can be a 1, 2, or 3 depending on what precedes and what follows). So, if you are interested, read Driving in Competition (I found it at the local library) or a similar book.

I’ll try to apply some of the above 1, 2, 3 analysis to a sample Championship course in the next Solo Line, “Addiction.”

Read original blog post