Two very important things happened at Nationals 2002.

The first was that immediately after winning a ProSolo Championship, on the same surface, and in similar conditions, the car changed from a winner to a spinning, undriveable pig.

The second was that Carroll Smith gave a tech seminar where we were able to bombard him with questions for the better part of four hours.

Out of both of these events came the conviction that we simply didn't understand enough about the way the suspension on the car worked, and that if we wanted to keep on winning, that had better get addressed before next season.

Carroll insisted that a large part of that process was making an accurate kinematic model of the suspension, and he recommended using WinGeo3, produced by Bill Mitchell Software. Who am I to argue with the author of Tune to Win?

So we bit the bullet, bought the software, and started making the model.

The poor innocent victim, awaiting measuring.

Measuring the car involves projecting the location of all the suspension pivot points onto a plastic sheet, using a plumb bob. Here is a point on the rear suspension being plotted.

The finished projection of the rear suspension, after plotting the axis and measuring all the points. From this comes a list of points in 3-space which the software uses to form the model.

And here's the model of the rear suspension. It can be moved through its entire range of motion, and all the relevant data examined.

Like this - a plot of steer vs suspension travel. It can be seen here that the suspension toes in in both bump and droop.