SCCA Autocross 2018 PAX Index comparison

It’s that time of year again.  Rick Ruth has updated the 2018 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 quick comparison of 2018 and 2017.  Because the A-Mod and B-Mod cars had another fast year in 2017 the index factor for every other class has dropped.  The median change is .008 so if your class dropped more than that your PAX index got a little easier and if your class dropped less than that your PAX index just got a little harder.  Check out the color coded info-graphic below.

2018 PAX Index compared to 2017

(click on image to enlarge)

SCCA autocross 2018 PAX index RTP index changes comparison

Additional information about the RTP/PAX index is available on the official page here:

Want to learn more about the car that has reset the PAX index the past two years in a row?  Then check out the AutoXandTrack feature on the A-Mod car that is the fastest autocross car in the country.

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.

Leave a Reply

Your email address will not be published. Required fields are marked *