The 28 classes that compete in SCCA Club Racing Majors events:
TOURING
T1 - T4
faster ↔ slower
Stock production based cars
some changes allowed to wheels/tires and suspension
B Spec
Stock production based sub-compacts
some changes allowed to wheels/tires and suspension
PRODUCTION
EP / FP / HP
faster ↔ slower
Production based cars
a range of performance modifications allowed but retain original design, structure and drive layout
SUPER TOURING
STU / STL
stu = up to 3.2l / stl = up to 2.0l
Production based cars
modifications to their drivelines and bodywork
STU = World Challenge® Touring Car based
GRAND TOURING
GT-1 / GT-2 / GT-3 / GT lite
faster ↔ slower
Purpose-built, highly modified “silhouette” replicas of series-produced sports sedans
GT cars are permitted tube-frame chassis with performance being equalized by allowing cars with smaller engines to compete at a lighter weight
FORMULA
Purpose-built open wheel / open cockpit race cars
Formula Atlantic® (FA), Formula 1000 (FB), Formula SCCA® (FE), Formula Continental® (FC), Formula Mazda (FM), Formula F (FF), Formula 500 (F500) and Formula Vee® (FV)
SPEC MIATA
Production based cars from Mazda
SPORTS RACING
P1 / P2 / SRF
Prototype 1, Prototype 2 and Spec Racer Ford
SEDAN
AS - American sedan
Notes:
The GCR (General Competition Rules) click the link (huge PDF)
for individual class look under Section 9 Cars and Equipment