It’s that time of year again. Rick Ruth has updated the 2021 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.
AutoXandTrack put together a comparison of 2021 and 2020. After the cancelation of so many national events and Solo Nationals it’s no surprise that 2021 saw very few changes. Based on the strength of the new Falken Azenis RT660 tires the SSC class gets the dubious honor of the biggest SCCA PAX adjustment.
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!
2021 PAX Index compared to 2020 (updated for XS changes)
(click on image to enlarge!)
Additional information about the RTP/PAX index is available on the official page here: http://solotime.info/pax/
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.