• Stock vehicles are basically as they come from the factory.  Best allowable modifications - R-type DOT tires on stock size wheels, shock absorbers, wheel alignment, cat back mufflers, front sway bar.

• Street Prepared are stock vehicles with external engine mods and basic handling upgrades.  Best allowable modifications - R type DOT tires on any size wheels, limited slip differentials, lowering, springs, engine bolt on items such as headers and air cleaner boxes.

• Prepared cars are heavily modified production based vehicles with no tire restrictions.  Racing engines (within displacement limits), racing brakes, chassis stiffening and light-weight glass and body panels (lexan and carbon fiber respectively) are allowed.

• Modified cars in general are single seat vehicles designed for racing.  Wings are just one of the reasons that this class is VERY, VERY fast.  Money and talent are your only limitations.  Street Modified is a class for production based cars but almost anything goes here.

To help understanding, the PAX chart below breaks these classes apart a little further.  The chart below has 6 classes of vehicles based on speed potential; Street Touring, Stock, Street Prepared, Formula, Prepared and Modified.

• Street Touring is a class for the lover of imported sub compacts and street tires.  This class allows the bolt-ons that are popular on the street today.

• Formula is all karts except for FSAE which is a new class for the Formula SAE vehicle that many top Universities sponsor.

If you are just starting out...before you modify your vehicle run a couple of events in the Street Touring or Stock classes...they are faster than you might think.  Remember, driver experience (and tires) is much more of a factor to the lap time than the vehicle!

Check the SCCA rulebook for details on allowable chassis, engine, suspension details for each class.

 Ben Clement over at azsolo.com (Arizona SCCA) has generated a pretty good pdf with modifications and what classes can run them, check it out before you make changes or when trying to decide what class to run in.