This section is intended to provide an overview of the rules structure for Solo I and II, focusing primarily on car preparation. The full Rules appear in the Solo I & II Rulebook, which is available from the National Office and often from your local Region. New Solo Rulebooks are released each winter.
Solo I rules are found in the 1996 Solo I & I Rulebook, available from the National Office. Updates to the rules are published periodically in SportsCar magazine, which is sent to all SCCA members. The Solo I rules heavily reference the SCCA General Competition Rules, also available from the National Office. Solo I does not have its own car classes as such, but rather provides places for cars classed by Club Racing and cars classed under Solo II Stock and Street Prepared rules to compete. All cars must be equipped with full roll cages and drivers must have proper safety equipment, as outlined in the Solo I & II Rulebook.
Solo II rules provide for 4 preparation levels, and provide places for SCCA Road Racing cars to compete in Solo, albeit with no guarantee that Road Racing cars will be competitive at the top levels.
These cars are fairly close to cars that are driven on the street, and are usually dual purpose automobiles. Permitted modifications include any DOT-approved tire, any shock that attaches to the stock mounting points, any exhaust from the catalytic converter back (subject potentially to local sound control), any brake pads, any front sway bar, any wheels of stock dimensions and offset, and addition of a race harness.
Cars prepared to Road Racing Showroom Stock rules are permitted to run in Stock, but are not permitted to "mix" rules between the two classes.
Street Prepared cars are allowed significant modifications over stock, but many are still dual-purpose cars. Some of the permitted modifications are: any legal modification in stock; any springs that fit stock attachements; any sway bars; any wheels & DOT-approved tires; any induction for the engine (except that cars that were originally normally aspirated must remain normally aspirated); and any exhaust including headers. Compression ratio and camshafts in the engine must remain stock.
Cars prepared to Road Racing Improved Touring and American Sedan rules are permitted to run in Street Prepared, but as with Showroom Stock, rules "mixing" is strictly prohibited.
Prepared cars are allowed very substantial modifications; Prepared cars are rarely licensed for street use. Interiors may be gutted, cams and pistons are free, and suspensions may be significantly modified.
Cars prepared to Road Racing GT and Production rules are permitted to run in Prepared.
Several types of cars run in Modified: Formula Cars and Sports Racers from Club Racing, and cars that once were street cars but which have received modifications pushing them out beyond the bounds of Prepared.