Slipstream - March 2006

Inside the 2006 AX/TT Rules
By Charlie Davis
When James Shoffit and I approached Rocky last fall and suggested
forming an Autocross Rules Committee, it had been 5
years since anybody had looked at the Rules. Well, there was a
copy on the web site, but nobody seemed to read them or pay much
attention to them anymore.
Rocky approved our idea of a Rules Committee consisting of the AX
Chair, the TT Chair, the Timing guy, the Truxster Driver, and Lisa Steele.
Our initial reason for forming this committee was to devise a
different way to select the Top Drivers. The old process had a problem:
Many classes only had one driver and without competition, it was
impossible to be selected as one of the Top Drivers!
At our first meeting, we quickly found consensus that part of the
problem was too many classes. We additionally decided to “invent” a new
algorithm that indexed drivers within class boundaries. Indexing is
controversial, because it’s difficult to do well. There are two primary
ways: 1) Collect historical event results and compile this into figures-ofmerit
for car models, and 2) Analyze each car technically and compute a
figure-of-merit for each model. The first approach is common (the
SCCA uses it, for example to generate their PAX index), but it is plagued
with sensitivities to both venue and driver. If you can collect lots of data
across many venues and drivers, this is acceptable. Unfortunately, with
only three venues and a total of about 100 AX drivers, we could do
neither. So we pursued the second option. We called the index the
“Predicted Performance Factor” or PPF for shorthand.
Bumping is an old, some say discredited technique where, as a car
collects modification points and passes a threshold value, it “bumps” up
a class. An advantage of the PPF approach is that it somewhat validates
bumping by solving one problem that discredited it: Classes organized in
historical order rather than ascending performance. The other objection
to bumping is that it requires dissimilar models to compete. We
wondered, for example, is it fair for a Cayenne to compete with a 356? In
fact, we virtually never see either one at an AX or TT, but if we did, they
might have to compete.
Our goal being good competition, we decided to have only 10
classes. We realized that with only 10 classes we would have to mix
models more than in the past. As we delved further, it became obvious
that most of the reasonably stock cars should fall into the bottom 7
classes; the upper 3 should be reserved for highly modified cars. Then we
realized that a modified 356 would probably not get beyond class 3 or 4!
Would a stock class 4 entrant (say a 2.7L 944) be upset if a race prepped
356 joined the class? The simple answer was,“Not if he beats the 356 race
car!” We asked several drivers. They all agreed with the unanimous
opinion of the Rules Committee; that competition was an important
part of their AX and TT enjoyment.
One of the big issues with the PPF approach is that it requires lots
of data. Some of the data we needed was in the Owners Manuals, Parade
Competition Regulations, Club Race Rules, Tech Spec Books and Shop
Manuals. What we didn’t find was often on a web site (some of that data
is questionable). We sent letters to the PCA Technical Committee for a
few gems. After about 3 months of work, we still have a few “holes” in the
data. Today, there are 102 different models in the list. We continue to
gather data and correct typos.
As we started piecing the PPF algorithm together, we created an
Excel spreadsheet. It’s quite complex, but only the Rules Committee
needs to delve into the “guts”. We did this work to make it easy to
classify a car. All an owner has to do is to answer a few car questions and
the classification is automatic. For a stock car you need to describe the
model and year (and for some cars, select which engine you have). If your
car is modified you must provide data about some of the modifications.
For example, if your car is lower than stock, you must supply the height
of the car at the top of the roof. If you can’t figure out how to measure it,
we’ll help (it’s actually quite simple). If you still can’t (or won’t) make the
measurement, we’ll do it for you. Our PPF scheme requires the actual
condition of the car to be known. Note that I didn’t say “if you modified
it” or “if you lowered your car”! If you bought it in a modified condition,
you have to figure out what the previous owner(s) did. Sorry…
We think most owners will have to use at least part of the
“modified” section, as most people have tires that aren’t stock.
James is converting the Excel spreadsheet to a web-based
application. It’s actually fun.You can play “what if”and see the effects…it
shows the Mod Points, the PPF, the Class, and where the car sits within
the class. The AX/TT Class Calculator will be used in conjunction with
on-line AX/TT Registration. In order to compete, you must be classified.
James will keep a class database for all competitors. You must classify
your car before your first AX/TT and if you change anything that would
affect your class, you must reclassify your car. It’s an honor system…
We are making some other changes. We will call the 10 classes
“open” classes. By this, we mean that they are open to anyone; lady
drivers can choose to compete with the men in these open classes. Some
ladies have been quite vocal about being forced to compete only with
other ladies! There is nothing to make ladies inferior to men at an AX. So,
in 2006, any lady can choose to compete with the guys. Those that don’t
like this option, can compete in a single, indexed Ladies Class. That’s a
change from the past, where we had 17 un-indexed Ladies Classes.
Usually only a few ladies showed up and populated a couple of these
classes. We will use the PPF to normalize the results within the new
Ladies Class. We’ll also index the Developing Driver Class the same way.
Drivers of either sex can chose to enter the Developing Driver Class.
Over the past several years, we have changed our timing and process
of running cars. A goal was to decrease the interval between cars. We now
routinely start a car every 25 seconds. We can do it faster but it’s pretty
hectic. This improvement was to enable us to give more runs. We
normally give 8-10 runs. The downside of our success is that the first
runs are essentially practice runs. This is counter to accepted AX norms,
where 2-3 runs are considered “right”; it’s OK to practice at a Time Trial,
but not at an Autocross.
The 2006 Rules say that our AXes (not TTs) will offer between 3 and
5 runs. At first, many think it’s silly or even evil to stop at 5, when we have
time for 10. Consider this an opportunity! We might have 2 events on one
day. In the AM, run AX#1. During lunch, change the course and in the
PM, run AX #2. We still get 8-10 runs and don’t bastardize the event by
allowing practice. Plus, it’s more flexible. Drivers will be able to choose AX
#1, AX #2, or both. For events where we don’t double up, we’ll still have
lots of extra runs (“fun runs”) for everyone after the 5 official runs. The
only difference will be that there will be pressure to peak early, not late.
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