Car classification depends not only on its model but also on the type and extent of changes (if any) made to the regular car. Improvements and alterations will cause a car to progress into a more competitive class if sufficient class-progression points are accumulated.

Some modifications are "free," that is, allowed without effect on classification charts. Other changes from stock are considered to affect performance significantly and, therefore, are handicapped (on the classification charts) through the weighted class-progression points. The "weighting" is established in such a manner that some specific modifications are, in effect, "free" for the Improved classes and still others, are in effect, "free" for the Modified classes. This allows a car that has progressed into a higher category to have the other modifications that typify the category and, therefore, be competitive its category.

The Summary Of Modifications Allowed provides an overview, but not a definition, of what modifications are handicapped for what categories, and what modifications are not allowed in certain categories.

You can view a further description of car categorization through handicap points.

There is also a car categorization worksheet for your use.