Class A – Ultimate Racing Series: Cars similar to F1, Indie, etc.

Class S – Stock Car Racing Series: Cars similar to North American stock cars

Class T – Touring Car Racing Series: Cars similar to DTM

Class H – Historic Car  Series: Legendary out of production Cars (Open Series)

Class F – Fantasy Car Racing Series: Cars with no prototypical reference. This class includes combat capable vehicles eqipped with machine guns or grenade launchers, emp discharger, oil spiller, nail carpet dispenser and what not.

Class X – Concept Car Racing Series: Futuristic and Concept cars. As opposed to Fantasy Cars, this class represents fully develloped car concepts, potentially based on real world calculations of bhp, torque, mass, etc.

Class R – Truck Drag Racing Series (Truck Rodeo, Open Series): Heavy Semi Trucks in Solo and Semi+Trailer Drag races

Class D – Drag Racing Series (Open Series)

Class O – Dirt Track Racing Series (Open Series): Cars similar to Off Road Buggys, PickUps, Crawlers, etc.

Sprint Racing Series: Classes STHFX

Drift Racing Series: Classes STHFX

Racing Series are essentially Scenario Descriptions, that put vehicles and rules into context and award points consitently.

Prototype Racing Series Car Specs Reference

IZOD Indie Car: http://en.wikipedia.org/wiki/IndyCar_Series#Specifications_.282012-present.29

NASCAR Sprint Cup: http://en.wikipedia.org/wiki/Sprint_Cup_Series#Specifications

NASCAR Nationwide: http://en.wikipedia.org/wiki/Nationwide_Series#Specifications