2012 NCR PAX Information
What is PAX?
The PAX (Professional Auto-X) Index has been used by SCCA and other clubs for years. It is a handicapping system that attempts to account for performance differences between car classes allowing the drivers' performances to be compared. A PAX factor is assigned to each class or subclass; the faster the class, the higher the factor. The fastest cars have a PAX factor of 1.000; other PAX factors are a percentage based on performance potential relative to the fastest cars. Each driver's actual time around the course is multiplied by their car's PAX factor to calculate their PAX time. This PAX time is also called their indexed time or factored time. PAX times can then be compared across classes.
It is impossible to come up with a PAX index that is perfect just as it is impossible to come up with a class system that is perfect. Everyone believes that someone else has a softer(i.e. easier) PAX factor.
What is an Indexed Class?
An indexed class is a class that combines several classes into one class and uses factored times to compare the results. For several categories we do not get enough entries to populate the individual classes so we need to combine multiple subclasses. By forming indexed classes. the factored (aka indexed) times provide a more equitable comparison of the results than the raw times.
NCR Autocross uses several indexed classes:
- All Porsche Novice entries are combined into a single indexed class, N.
- Strict Stock subclasses S1-S5 are combined into a single indexed class, 1S.
- Strict Stock subclasses S6-S8 are combined into a single indexed class, 2S.
- Production subclasses P1-P2 are combined into a single indexed class, A.
- Production subclass P3 forms the indexed class, B.
- Production subclass P4 forms the indexed class, C.
- Production subclass P5 forms the indexed class, D.
- Production subclasses P6-P9 are combined into a single indexed class, E.
- All Improved and Modified subclasses are combined into a single indexed class, R.
- All non-Porsche entries are combined into a single indexed class, X.
- All non-Porsche Novice entries are combined into a single indexed class, Z.
The NCR PAX Index
The NCR PAX Index is based on the PAX/RTP Index. developed by Rick Ruth. that is based on hundreds of autocross events nationwide. Some explanation of the NCR charts and how we arrived at the numbers we use follows. First for the Production Stock and Strict Stock chart:
| Column | Description |
|---|---|
| Subclass | NCR Production Stock and Strict Stock subclass names. |
| Models | The car models which make up the respective subclasses. This information is from our Autocross Rules. |
| SCCA Class | The SCCA class for each model. |
| SCCA PAX | The SCCA class we use for each of our Production/Strict Stock subclasses. All models which make up one of our subclasses are generally in the same SCCA class. This makes coming up with a PAX factor easy because we just used the SCCA class PAX For example, several different car models make up our subclass P4, but each one of them is in the SCCA C-stock (CS) class, so we use the CS PAX factor). |
| Production PAX Factor |
The SCCA PAX factor for each Production Stock subclass. |
| Strict Stock PAX Factor |
The SCCA PAX factor for each Strict Stock class. These factors are calculated using a two second handicap over the corresponding SCCA PAX. This is based on the commonly accepted assumption that R-compound tires make a car about two seconds faster than street tires. |
| 60 sec | Shows the raw time needed for a factored time of 60 second raw time in this class. Here you can see how much time you'll be giving, or gaining, from your friends. |
The Improved and Modified charts are similar but these categories are more of a problem because these subclasses do not map easily to the SCCA classes. However, the Improved Category is similar to the SCCA Street Prepared (SP) and Street Modififed Categories (SM) so we map the range of SP PAX factors from DSP to SSM evenly over the range of NCR Improved classes. A range of SCCA Prepared classes (DP, FP, BP, XP) and Modified classes (DM, EM) map to the NCR Modified subclasses so we map the range of PAX factors from DP to EM evenly over the range of NCR Modified classes. Again, the mappings are not perfect but it does provide a progression of PAX factors allowing for a more equitable comparison of results between the individual classes that are included in the indexed class.
For the non-Porsche classes we simply use the PAX factors for their SCCA classes.
