The PAX index was developed by Rick Ruth and reflects study of results from well over 500 nationwide Solo events. The below information is sourced from the official PAX webpage.
| Category | Class | Multiplier (2018) | Multiplier (2017) | Difference |
|---|---|---|---|---|
| Street | A Street | 0.814 | 0.819 | -0.005 |
| Street | B Street | 0.808 | 0.813 | -0.005 |
| Street | C Street | 0.805 | 0.810 | -0.005 |
| Street | D Street | 0.794 | 0.801 | -0.007 |
| Street | E Street | 0.787 | 0.794 | -0.007 |
| Street | F Street | 0.797 | 0.804 | -0.007 |
| Street | G Street | 0.786 | 0.793 | -0.007 |
| Street | H Street | 0.781 | 0.786 | -0.005 |
| Street | Super Street | 0.817 | 0.826 | -0.009 |
| Street R | Super Street R | 0.838 | 0.847 | -0.009 |
| Solo Spec | Solo Spec Coupe | 0.806 | 0 | |
| Street Touring | Street Touring Hatch | 0.811 | 0 | |
| Street Touring | Street Touring Pony Car | 0.815 | 0.820 | -0.005 |
| Street Touring | Street Touring Roadster | 0.823 | 0.830 | -0.007 |
| Street Touring | Street Touring Sport | 0.810 | 0.818 | -0.008 |
| Street Touring | Street Touring Ultra | 0.824 | 0.831 | -0.007 |
| Street Touring | Street Touring Xtreme | 0.813 | 0.822 | -0.009 |
| Street Prepared | A Street Prepared | 0.848 | 0.856 | -0.008 |
| Street Prepared | B Street Prepared | 0.846 | 0.853 | -0.007 |
| Street Prepared | C Street Prepared | 0.857 | 0.860 | -0.003 |
| Street Prepared | D Street Prepared | 0.835 | 0.842 | -0.007 |
| Street Prepared | E Street Prepared | 0.828 | 0.837 | -0.009 |
| Street Prepared | F Street Prepared | 0.819 | 0.829 | -0.01 |
| Street Prepared | Super Street Prepared | 0.852 | 0.862 | -0.01 |
| Street Modified | Street Modified | 0.853 | 0.861 | -0.008 |
| Street Modified | Street Modified FWD | 0.839 | 0.848 | -0.009 |
| Street Modified | Super Street Modified | 0.871 | 0.875 | -0.004 |
| Prepared | B Prepared | 0.860 | 0.869 | -0.009 |
| Prepared | C Prepared | 0.847 | 0.854 | -0.007 |
| Prepared | D Prepared | 0.858 | 0.865 | -0.007 |
| Prepared | E Prepared | 0.850 | 0.859 | -0.009 |
| Prepared | F Prepared | 0.863 | 0.873 | -0.01 |
| Prepared | X Prepared | 0.884 | 0.892 | -0.008 |
| Modified | A Modified | 1.000 | 1.000 | 0 |
| Modified | B Modified | 0.956 | 0.956 | 0 |
| Modified | C Modified | 0.890 | 0.901 | -0.011 |
| Modified | D Modified | 0.895 | 0.906 | -0.011 |
| Modified | E Modified | 0.894 | 0.905 | -0.011 |
| Modified | F Modified | 0.904 | 0.916 | -0.012 |
| Modified | Kart Modified | 0.928 | 0.939 | -0.011 |
| Formula | Formula SAE | 0.958 | 0.966 | -0.008 |
| Formula | Formula Junior A | 0.855 | 0.864 | -0.009 |
| Formula | Formula Junior B | 0.825 | 0.834 | -0.009 |
| Formula | Formula Junior C | 0.718 | 0.726 | -0.008 |
| CAM | Classic American Muscle Contempory | 0.816 | 0.823 | -0.007 |
| CAM | Classic American Muscle Sport | 0.831 | 0.838 | -0.007 |
| CAM | Classic American Muscle Traditional | 0.807 | 0.817 | -0.01 |
| Heritage Classic | Heritage Classic Race Tire | 0.812 | 0.825 | -0.013 |
| Heritage Classic | Heritage Classic Street Tire | 0.791 | 0.809 | -0.018 |
| Category | Class | Multiplier (2018) | Multiplier (2017) | Difference |
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Written by Rocky Entriken, this is the record book of 52 years of the Sports Car Club of America's National Solo (autocross) championships from its beginning in 1973 to 2025, including a brief history of the sport and the championship. It includes the final placing of every driver who has ever competed in the annual event.
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