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Thread: SCCA Solo Car Categories, a primer

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    SCCA Solo Car Categories, a primer

    Solo® Car Classifications
    The following information is from the SCCA® National Solo® Rules. Please
    consult those rules for specific information regarding allowable modifications and guidelines. If you are interested in a copy of the SCCA® National Solo® Rules, you can download it from or you can call the SCCA® National Office at 1-800-770-2055. For questions and/or information concerning the Solo® Rules, contact Doug Gill, SCCA® Solo® Competition Manager at [email protected] or call 1-800-770-2055.


    Stock – This category includes mass-produced, common vehicles that may be “daily drivers” (cars used for normal, everyday driving). Stock Category cars compete in their “factory” configuration with a minimal number of allowances (not requirements) such as:
    - Removal of spare tire and tools
    - Front anti-roll bar(s)
    - Suspension/wheel alignment using standard adjustments
    - High-performance DOT tires (including competition R-compounds)
    - Shock absorbers/struts (2 external adjustments maximum)
    - Competition-type seat belts (no shoulder belts in open cars)
    - Brake linings (pads/shoes)
    - Air filter element (the “throw-away” part)
    - “Cat”-back exhaust systems
    - Wheels of standard size (diameter, width, and offset within ¼”)
    - Roll bar/cage
    - Gauges, indicator lights, etc.
    Please refer to the SCCA® National Solo® Rules for more details and specifics.

    Street Touring® – Started in 1997, this is one of the more popular categories which includes Street Touring® Sport (STS), Street Touring® Sport 2-seater (STS2), Street Touring® Xtra (STX), and Street Touring® Ultra (STU). This is the only category that does not allow competition R-compound tires – only high performance tires with a UTQG treadwear rating of 140 or higher.

    STS consists of sedans/coupes with four seats minimum and normally aspirated engines up to 3.1L (very few turbo/supercharged cars are allowed).
    - Stock category allowances
    - No limited slip differentials except for standard viscous-types
    - Pedal kits and other interior trim
    - Front seats (15 pounds minimum weight each)
    - Rub strips, emblems, and mud flaps removed
    - Body kits, spoilers, and wings added
    - Tires up to 225 mm wide, UTQG treadwear 140 minimum
    - Wheels up to 7½ inches wide, any diameter/offset
    - Shocks/struts
    - Drilled/slotted rotors (standard size) and braided DOT brake lines
    - Anti-roll bars, front and rear
    - Lowered suspensions using standard-type springs
    - Suspension bushings (non-metallic)
    - Camber kits, plates, or bolts
    - Traction bars, torque arms, panhard rods
    - Strut bars, 2-point only
    - Battery relocated
    - Air filter systems up to throttle body or compressor inlet
    - Headers, emissions compliant
    - Engine computers (PCM/ECU) reprogrammed
    - Shifter kits
    - Accessory drive pulleys
    - Motor mounts (non-metallic)
    - Example of included cars: Audi A4 1.8T and TT (non-quattro), Mazda 323 GT and GTX (AWD), Volkswagen Golf/GTi/Jetta/Beetle/Passat 1.8T and TDI,
    Volvo S40 (except T5) and V40
    - Example of excluded cars: Datsun Z 2+2, Honda CRX, MGB GT, Porsche
    (all), Triumph (all)

    STS2 is for sports cars with 2 seats and normally aspirated engines up to 1.9L.
    - STS allowances
    - Included cars: BMW Z3, Honda CRX and del Sol, Mazda Miata (1990-97) and
    RX-7 (1979-92) (non-turbo), Toyota MR2 (1985-89) (non-supercharged)
    - Excluded cars: Lotus (all), Mazda Miata (1999+), Toyota MR2 (1991-95,

    STX is for sedans/coupes with four seats and engines up to 5.1L normally aspirated or up to 2.0L turbo/supercharged.
    - STS allowances
    - Tires up to 245 mm wide, UTQG treadwear 140 minimum
    - Wheels up to 8 inches wide, any diameter/offset
    - Limited slip differentials allowed (including aftermarket) for 2WD cars
    - High-flow “cat”
    - Larger brake calipers and rotors

    Excluded cars: Audi S4 (V8 engine), BMW M3 (E36, E46) and M5, Mitsubishi
    Lancer Evolution, Subaru Impreza WRX STi, Mazda RX-8

    STU is for sedans/coupes with four seats and normally aspirated engines of any displacement normally aspirated or turbo/supercharged engines up to 3.1L.
    - STS and STX allowances
    - No wheel restrictions
    - Tires for 2WD cars up to 275 mm wide (245 for AWD)
    - Example of included cars: Audi S4, BMW M3 (E36), Chevrolet Camaro, Dodge
    SRT-4, Ford Mustang, Mazda RX-8, Mitsubishi Lancer Evolution, Pontiac
    Firebird / Trans Am and GTO, Subaru Impreza WRX STi, Volvo S60 R,
    Toyota Supra
    - Excluded cars: BMW M3 (E46) and M5 (E39)
    Refer to the SCCA® National Solo® Rules for full details and specifications on
    the Street Touring® allowances.

    Street Prepared – The original SCCA® “street” category, Street Prepared allows any carburetor/fuel injection system and any ignition system. Turbo/supercharger hardware has to remain standard, but aftermarket boost control systems/programs and intercoolers are allowed. Exhaust manifolds and systems are free. Emission controls are not required for competition, but no internal engine or transmission modifications are allowed beyond factory specs (no cams, hi-comp pistons, ported heads, etc). Some cars are able to update/backdate components like engines, brakes, etc (See Solo Rules for details and specifics). There are no limits on wheels sizes or DOT tires; racing springs and shocks are
    the norm.

    Street Modified – The top of the “street” categories, Street Modified allows anything from Stock, Street Touring, and Street Prepared and just about any engine and drivetrain configuration as long as the engine manufacturer matches the body manufacturer (see Solo Rules for details). Four-seaters (BMW, Corolla, Civic, Integra, Neon, Supra, Talon, VW, etc.) run in SM and two-seat sports cars (Corvette, CRX, M Roadster, Miata, RX-7, MR2, etc.) compete in SM2. Carbon fiber hoods, cams, turbo/supercharger kits, etc are welcome, too.

    Prepared – These cars are not for the street; they are virtually race-prepared vehicles for dedicated Solo® competition. Gutted interiors and racing slicks are the first visual characteristics of these cars and when they crank up, you can tell these engines weren’t built for bringing home the groceries. Convertible cars are required to install roll bars per the Solo Rules.

    Modified – Except for D and E Modified, these were never ever “street” cars. They are special built competition vehicles and most of them resemble an open wheel Indy car or a closed-wheel LeMans sports racer. DM and EM cars may have started life on the streets, but just about any engine, drivetrain, or suspension is permitted. Supercharged rotary engines and V-8 engines are seen in 1700-pound EM machines and powerful 4-cylinders are common in 1300-pound DM lightweights.
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