UPDATED April 2020 for additional changes! It’s that time of year again. Rick Ruth has updated the 2020 PAX Index, aka Racer’s Theoretical Performance index, for autocross. PAX is the SCCA’s system for comparing the performance of cars from different classes against each other.
12/4/2019 update. As a result of the new 2020 CAM rules the PAX factors for CAM-C and CAM-T have been updated. Clearly Rick Ruth believes that the 4th gen Camaro and SN 95 Mustang have similar potential to the modern muscle cars. There is now virtually no difference in the PAX between the two classes. CAM-T just got .24 seconds harder (on a 60 second course). Also, FS, STH and SS have been changed.
AutoXandTrack put together a quick comparison of 2020 and 2019. For the most part 2020 saw very minor changes in almost all classes. The primary exception being CSP and DP and to a lesser extent DS. The median change is .000 or 30 thousands of a second on a 60 second course. Or in other words no change.
If your class increased more than that, your PAX index got a little harder and if your class dropped or increased less than that, your PAX index just got a little easier. Check out the color coded info-graphic below.
We’ve also included the time increase or decrease on a 60 Second course. In other words if your buddies’ PAX didn’t change, but yours went up by .005 then you need to run 3 tenths faster in 2020 to keep up!
2020 PAX Index compared to 2019
(click on image to enlarge!)
Additional information about the RTP/PAX index is available on the official page here: http://solotime.info/pax/rtp2020.html
Want to learn more about the car that has reset the PAX index the past few years in a row? Then check out the AutoXandTrack feature on the A-Mod car that is the fastest autocross car in the country.
Check out the new AutoXandTrack YouTube series!
If you are here, you must really like autocross! And when you aren’t at the track get your fix watching our event coverage and more. Here is a sample episode.
How is the RTP / PAX Index determined?
The RTP / PAX Index was developed by Rick Ruth and reflects study of results from well over 500 nationwide Solo events with a history going back to the 1970’s.
There are two common misconceptions about PAX when folks first encounter it. First, they don’t understand how it can be applied to themself or their own car as others might not have a car setup exactly like they do. Second, why is a pax “softer” or easier for a class that on paper should be faster.
The thing to keep in mind is that the RTP / PAX index is based on real world results for each “class” (not car). By comparing actual results from national level events and large regional events you can come up with a good (but not perfect) benchmark about how typical cars perform against each other. If your car isn’t prepped to a nationally caliber level or you are a newer driver then you probably won’t do as well on a PAX adjusted basis. The index is updated once a year, each year.