[SCCA] Solo I & II Car Classification Rules: 
Street Prepared

This is an unofficial transcription of Section 14 of the 2003 SCCA National Solo Rules. (Copyright Sports Car Club of America 2003; all rights reserved) It is believed to be correct, but any questions should be referred to the official rules as published by the SCCA. Order your own copy here.

Changes since the 2002 Rules are shown like this;
Further changes from FasTrack are shown like this.


  • 14.1 Authorized Modifications
  • 14.2 Bodywork
  • 14.3 Tires
  • 14.4 Wheels
  • 14.5 Shock Absorbers
  • 14.6 Brakes
  • 14.7 Anti-Roll (Sway) Bars
  • 14.8 Suspension
  • 14.9 Electrical System
  • 14.10 Engine and Drive Train
  • 14.11 Out-of-Production Cars


    Cars running in Street Prepared Category must have been series produced with normal road touring equipment capable of being licensed for normal road use in the United States, and normally sold and delivered through the manufacturer's retail sales outlets in the United States. Cars not specifically listed in Stock or Street Prepared Category classes in Appendix A must have been produced in quantities of at least 1000 in a 12 month period to be eligible for Street Prepared Category.

    A vehicle may compete in Street Prepared Category if the preparation of the vehicle has not exceeded the allowable modifications of Stock Category, except as specified below. However, the distinction between different years/models used in Stock Category does not apply in Street Prepared Category. Example: Porsche 911 models that are listed on the same line are considered the same.

    Cars listed as eligible in and prepared to the current national Improved Touring rules are permitted to compete in their respective street prepared classes. Logbooks are not required. Neither Street Prepared nor Improved Touring cars are permitted to interchange preparation rules. Improved Touring cars may use tires which are eligible under current IT rules even if they are not eligible in Street Prepared.

    Cars listed as eligible in and prepared to the current American Sedan rules are permitted to compete in Class B Street Prepared. Logbooks are not required. Neither Street Prepared nor American Sedan cars are permitted to interchange preparation rules.  American Sedan cars may use tires which are eligible under current AS rules even if they are not eligible in Street Prepared.

    Cars listed as eligible in and prepared to the current national Touring category rules are permitted to compete in their respective Street Prepared classes.  Neither Street Prepared nor Touring cars are permitted to interchange preparation rules.  Touring cars may use tires which are eligible under current Touring rules even if they are not eligible in Street Prepared.

    While the rules of the Street Prepared Category have remained essentially the same, the laws governing various aspects of street-driven vehicles have changed over time. The original concept of this category as made up predominantly of street-driven vehicles has been rendered inappropriate. The SCCA does not encourage or condone the breaking of laws governing pollution control systems or the alteration of street-driven vehicles contrary to state and federal laws regarding their use. It continues to be the responsibility of the individual to comply with such state and federal laws.

    Specific vehicle classifications are located in Appendix A of these rules.

    14.1 Authorized Modifications

    1. All Allowable modifications permitted in Stock Category are allowed.
    2. Street Prepared vehicles may only be modified in excess of Stock Category rules in the following ways. Any modification not specifically authorized by the Stock Category or Street Prepared rules is prohibited. No unauthorized modifications are permitted in order to accommodate authorized modifications (i.e., non-stock hood scoops or holes necessary for carburetor clearance). Structural modifications, such as the addition of members known as "jacking rails", are not permitted unless specifically authorized herein.
    3. Equipment and/or specifications may be exchanged between different years and models of a vehicle if

    4. (a) the item is standard on the year/model from which it was taken,
      (b) the years/models are listed on the same line of Appendix A (Street Prepared Classes).
      The updated/backdated part or the part to which it is to be attached may not be altered, modified, machined or otherwise changed to facilitate the updating/backdating allowance. The updating and/or backdating of engines, transmissions or transaxles must be done as a unit; component parts of these units may not be interchanged. Cars not listed in the Street Prepared sections of Appendix A may not be updated/backdated until approved by the SEB and published in SportsCar magazine.
    5. Alternate computer control modules may be used whenever an equivalent change to the conventional system is allowed. For example, alternate computer module control of ignition settings or fuel injection is allowed. Direct turbocharger boost control by alternate computer control is not, since there is no equivalent mechanical allowance.
    6. Air conditioning systems may be removed in whole or in part. This rule should not be interpreted to allow modification of the heater system.
    Refer to Appendix F for past clarifications of these rules.

    14.2 Bodywork

    1. Fenders and bumpers (including the portion of the hood which serves as a fender/wheel well, 8/2003, but ONLY that portion  and not by complete hood replacement, 9/2003) may be modified for tire clearance. Flares may be added although tires may extend beyond the body work. Replacement of complete flared fenders or quarter panels is prohibited.
    2. Removal of factory trim is only permitted if the resultant configuration is an allowed update or backdate.
    3. Strut bars are permitted with all types of suspension. Strut bars may be mounted only transversely across the car from upper right to upper left suspension mounting point and from lower right to lower left suspension mounting point. No other configuration is permitted. Additional holes may be drilled for mounting bolts. Only bolt-on attachment is permitted.
    4. Any fully padded and upholstered front seat may be used. This does not permit the substitution of a passengers seat with a child or miniature seat of any type. Any substituted passengers seat must be sufficiently large and strong to be capable of adequately accommodating an adult, such that it could be used as the driver's seat. The OEM seat belts may be removed to facilitate the installation of alternate restraints complying with safety requirements.  Seat tracks are considered part of the seat and may be substituted when an alternate seat is installed. (3/2003)
    5. Any steering wheel may be used.  An alternate wheel which replaces an airbag-equipped wheel is not required to have an airbag.  The alternate wheel is not required to have a horn button. (3/2003)
    6. Spoilers and cosmetic trim pieces are permitted. Side skirts may not be used. Spoilers must comply with the following subsections. The intent of this allowance is to accommodate commonly available appearance kits, and replicas thereof, which have no significant aerodynamic function at Solo II speeds.
      2. A spoiler may be added to the front of the car below the bumper. It may not extend rearward beyond the front most part of the front wheel well openings, and may not block normal grille or other openings, or obstruct lights. Openings may not be used for the purpose of ducting air to the radiator, or oil cooler, but they may allow air to flow through a permitted oil cooler provided no ducting is used.  The spoiler may not function as a wing.
      3. A spoiler may be added to the rear of the car provided it complies with either of the following:
        2. It is a production rear spoiler which is standard or optional equipment of a U.S. model of the vehicle, or an exact replica in an alternate material.
        3. It is a non-production rear spoiler which is mounted to the rearmost portion of the rear hatch, deck, or trunk lid. The spoiler may extend no more than 10 inches from the original bodywork in any direction. Alternatively, in a hatchback, the spoiler may be mounted to the rear hatch lid at or near the top of the hatch; in such a configuration the spoiler may extend no more than 4 inches from the original bodywork in any direction. The spoiler may be no wider than the bodywork, and it shall not protrude beyond the overall perimeter of the bodywork as viewed from above. The use of endplates is prohibited. Angle of attack is free. The spoiler may not function as a wing.
    7. Roll bars and cages must comply with Section 13.2.G in Stock category.  Roll cages must comply with the following:
      1. The roll cage need not be removable.  It shall be bolted or welded to the car.
      2. The cage shall attach to the car at no more than 8 points, consisting of the basic cage with 6 attachment points, and 2 additional braces.
      3. The forward part of the cage shall be mounted to the floor of the vehicle.  In addition, the 2 optional braces referred to in (b) may be mounted, one on either side, from the forward section of the cage to the firewall or front fender wells.  No braces shall pass through the front firewall.
    8. The use of a fuel cell which complies with current GCR requirements is permitted, provided all of the following additional restrictions are met:
      2. The capacity of the cell may differ by no more than 20% from that of the original tank.
      3. The location of the cell may differ from that of the original tank by no more than six inches in any direction.
      4. The car meets all applicable Solo I safety standards, including those for rollover protection and the installation of a fire extinguisher.
    9. Fuel tank changes are permitted only as allowed under 14.1.C and 14.2.H. No additional tanks or reservoirs may be used.
    10. Accelerator, brake, and clutch pedals may utilize substitute covers of unrestricted origin, shape, and size, provided they meet the following requirements: Covers must be securely attached, provide a non-slip surface, not interfere with each other's operation, and must be deemed safe at Tech Inspection.

    14.3 Tires

    Tires must meet the eligibility requirements for Stock Category with the following exception: The list of non-eligible tires in Section 13.3.A is replaced with the following list, which may be altered at any time by the SEB upon notification of membership.

    No tire models are currently listed.

    14.4 Wheels

    1. Wheels of any diameter, width, or offset may be used.
    2. Wheel spacers are permitted. Wheel studs and knock-off wheel drive pegs may be changed in length and diameter. Wheel bolts may be replaced with studs and nuts.

    14.5 Shock Absorbers

    1. Shock absorber bump stops may be altered or removed.
    2. On cars with lever-type shock absorbers, a tube-type shock absorber may be added. If the lever-type shock serves no other purpose, it must be removed. If the lever-type shock serves any other purpose, it must be retained.
    3. Any shock absorbers may be used, provided they attach to the original mounting points. The number of shock absorbers shall be the same as Stock. No shock absorber may be capable of adjustment while the car is in motion, unless fitted as orignal equipment. MacPherson strut equipped cars may substitute struts, and/or may use any insert. This does not allow unauthorized changes in suspension geometry or changes in attachment points (e.g., affecting the position of the lower ball joint or spindle).  It is intended to allow the strut length changes needed to accommodate permitted modifications which affect ride height and suspension travel.  This allowance differs from Improved Touring Allowance 12.1.4.d.5.d.1.

    14.6 Brakes

    Any brake line, single or dual master cylinder, vacuum brake booster, brake proportioning valves may be used. This does not allow multiple separate cylinders, but does allow for any single, dual-circuit cylinder.  "Safety breakers" and units such as the "Brake Guard System" are permitted. ABS braking systems may be disabled, but not removed; brake boosters may be removed or added.  Air ducts may be fitted to the brakes, provided that they extend in a forward direction only, and that no changes are made in the body/structure for their use.  They may serve no other purpose.  Backing plates and dirt shields may be modified or removed.

    14.7 Anti-Roll (Sway) Bars

    Any anti-sway bar is permitted. Bushing material, method of attachment, and locating points are unrestricted. This does not authorize removal of a welded-on part of a subframe toa ccommodate the installation. Components such as anti-roll bars and strut housings which serve dual purposes by also functioning as suspension locators may not be modified in ways which change the suspension geometry or steering geometry, and may not be installed in positions (e.g., upside down) other than that of the original configuration.  The bar may serve no other purpose which is not explicitly permitted elsewhere herein (11/2003).

    14.8 Suspension

    1. Ride height may only be altered by suspension adjustments, the use of spacing blocks, leaf spring shackles, torsion bar levers, or change or modification of springs or coil spring perches. This does not allow the use of spacers which alter suspension geometry, such as those between the hub carrier and lower suspension arm. Springs must be of the same type as the original (coil, leaf, torsion bar, etc.) and except as noted herein, must use the original spring attachment points. Coil spring perches originally attached to struts or shock absorber bodies may be changed or altered, and their position may be adjustable. Spacers are allowed above or below the spring.  These allowances permit multiple coil springs, as long as they use the original mount locations. (7/2003).
    2. Suspension bump stops may be altered or removed.
    3. Suspension bushings may be replaced with bushings of any materials (except metal) as long as they fit in the original location. Offset bushings may be used. In a replacement bushing the amount of metal relative to the amount of non-metallic material may not be increased. This does not authorize a change in type of bushing (for example ball and socket replacing a cylindrical bushing), or use of a bushing with an angled hole whose direction differs from that of the original bushing.  If the Stock bushing accommodated multi-axis motion via compliance of the component material(s), the replacement bushing may not be changed to accomodate such motion via a change in bushing type, for example to a spherical bearing or similar component involving internal moving parts. Pins or keys may be used to prevent the rotation of alternate bushings, but may serve no other purpose than that of retaining the bushing in the desired position.  Differential mount bushings are not suspension bushings and thus may not be substituted under this allowance, though Section 14.1.C allows certain update/backdate allowances (8/2003).
    4. On vehicles with strut-type suspensions, adjustable camber plates may be installed at the top of the strut, and the original upper mounting holes may be slotted. The drilling of holes in order to perform the installation is permitted but the center clearance hole may not be modified. Any type of bearing or bushing may be used in the adjustable camber plate attachment to the strut. The installation may incorporate an alternate upper spring perch/seat and/or mounting block (bearing mount). Any ride height change resulting from installation of camber plates is allowed.  Caster changes resulting from the use of camber places are permitted
    5. Addition or replacement of suspension stabilizers (linkage connecting axle housing or De Dion to the chassis, which controls lateral suspension location) is permitted. Traction bars or torque arms may be added or replaced. A panhard rod may be added or replaced. Methods of attachment and attachment points are unrestricted. This does not authorize removal of a welded-on part of a subframe to accommodate installation.  The longitudinal member which GM refers to as a "torque arm" on 3rd and 4th generation Camaros, which controls differential movement, is covered by this section and may be substituted or modified. 
    6. Changes in alignment parameters which result directly from the use of allowed components are permitted.  For example, the dimensional changes resulting from the use of a cylindrical offset bushing which meets the restrictions of 14.8.C are allowed, including those resulting from a change in the pivoting action to

    7. (a) about the mounting bolt, or
      (b) about the bushing itself.

    14.9 Electrical System

    1. Any ignition setting adjustment or system may be used.  An original ignition sensor on a cam cover may be removed, and the hole plugged.  This may serve no other purpose. (3/2003)
    2. The make, model number, and size of the battery may be changed but not its voltage.
    3. Relocation of the battery or batteries is permitted but not into the passenger compartment. If the battery is relocated and the original battery tray can be removed by simply unbolting it, the tray may be removed, or relocated with the battery.  Holes may be drilled for mounting or passage of cables. Longer cables may be substituted to permit relocation. The number of battery or batteries may not be changed from stock. The area behind the rearmost seat is not considered to be within the passenger compartment.
    4. Any starter, generator or alternator may be used in the original position. This does not allow for the use of an alternator or generator having little or no output. An alternator or generator must have an electrical output equal to or greater than the original equipment unit.  Any generator or alternator pulley and belt of the same type as standard may be used (see 14.10.U)
    5. Wiring harnesses may not be removed in whole or in part.  Wiring connectors for emissions control devices are considered part of the harness, not part of the emissions control system, and may not be removed.

    14.10 Engine and Drive Train

    1. Engines must retain standard type lubricating system, but may have any oil pan (Accusump-type systems allowed), oil pump and pickup, oil coolers, oil or fuel filters. Fuel filters must be of automotive type and serve no other purpose. A permitted oil cooler may be positioned in an opening in an allowed spoiler, provided no unauthorized modifications are made in order to perform the installation.
    2. Heat shields may be added.
    3. Carburetors, fuel injection, intercoolers and intake manifolds are unrestricted. Alternate throttle linkage and connections to facilitate installation of allowed induction systems are permitted, but may serve no other purpose. As utilized only on engines originally equipped with forced induction, air-to-air heat exchangers (known as "intecoolers"), and radiators which are part of air-to-liquid charge coolers, must be cooled only by the atmosphere.

    4. The use of chilled liquids, ice, dry ice, refrigeration systems, vaporized compressed gases, etc. is prohibited.   If an induction system item is allowed to be removed and its original mounting bracket can be removed simply by unbolting it, the bracket may be removed as well.  Turbochargers may not be added, changed or modified. Turbocharger and supercharger systems may only be updated/backdated with the accompanying engine unit. No changes are allowed to waste gates, pressure sensors or their location, and to other turbocharger or supercharger boost limiting systems.  This allowance does not permit changes to blow-off (pop-off) valves.  Devices known as "fuel cut defensers", and any modifications which alter or defeat the fuel cutoff when it is activated by boost level, are not permitted.

    5. Air cleaner(s) may be changed or removed, velocity stacks may be added.
    6. Emission control devices may be modified or removed.  This permits the oil filler cap to be modified or substituted, but does not allow valve covers or cam covers to be altered to install a breather or for any other purpose.
    7. Intake water injection systems are allowed.
    8. Fuel lines and pumps are unrestricted except as specified herein as long as they do not pose a safety hazard. Fuel lines may be no larger than 1/2" i.d. and may only connect to the original fuel tank or allowed fuel cell. They may be no longer than necessary for reasonable and safe installation, and may serve no other purpose. A single fuel feed line may be used. A single fuel return line may be used, and a fitting for connecting it may be added at or near the top of the fuel tank. This does not authorize "cool-cans".
    9. Exhaust manifolds and muffler systems are free, except that they must be quiet and terminate behind the driver. Exhaust heat shields may be removed. Rear- and mid-engined cars without exhaust headers/manifold systems may use any exhaust system that meets the requirements of 3.5. This permits the removal of "heater boxes" in order to install headers on such cars.
    10. One bolt-on torque suppression device may be used. A torque suppression device attaches from the engine to the body, frame, or subframe in one location, and controls engine movement at that location along a single axis only. It may serve no other purpose.

    11. Examples of permitted devices:
      1. ) a chain
      2. ) a rod with spherical bearings at each end.
      Examples of devices not permitted:
      1. ) one or more solid motor mounts
      2. ) any link which confines movement along more than one axis
      3. ) an engine mounting plate, or one or more plates rigidly bolted between the engine and the frame.
      Holes may be drilled to mount a torque suppression device. The installation may not include the welding of any plate(s) to the motor mount(s) or bodywork (7/2003), nor may it include multiple non-parallel links.
      This does not allow motor mount changes other than those which are update/backdates of factory components.
    12. The engine fan and fan shroud (unless it serves another purpose, e.g. as an alternator/generator mount) may be removed, modified or replaced. Electrically driven fans are allowed.
    13. On two-cycle engines, the ports must be of standard heights, size and configuration; crankcase volume and reed plates must not be altered.
    14. Any metal clutch assembly, metal flywheel or metal torque converter that uses the standard attachment to the crankshaft may be used. Non-metallic friction surfaces (e.g. clutch disks) may be used. Dowel pins may be added. Minor repositioning of the clutch slave cylinder is allowed to accommodate the alternate clutch, but the unit may not be relocated and the repositioning may serve no other purpose. This allowance does not permit the substitution of slave cylinders or the use of non-original methods of clutch actuation (e.g. pull type vs. push type).
    15. Any mechanical shift linkage may be used.
    16. Limited slip differentials are permitted. This permits locked differentials, either by design, welding, or mechanical means. Differential cases, internal differential parts, and axle stubs may be machined as required for clearance and installation to the extent that material may only be removed, not added, and the exterior of the case may not be altered in any way. This machining may serve no other purpose.
    17. Cylinders may be rebored to .0472 in. over standard bore and the appropriate standard oversize piston may be substituted. Cast or forged, non-stock pistons of the same dimensions and configuration as original equipment pistons may be used. Additionally the replacement pistons must be of the same weight or greater as the original equipment pistons.  The .0472 in. limit is absolute, no additional tolerance is permitted to accommodate wear.   This allowance does not permit alternative ring configurations. (3/2003)
    18. Rotating and reciprocating parts may be balanced but not lightened.
    19. Intake and exhaust ports and manifold openings may be matched provided no change is made more than one inch from the port/manifold interface.   Material may be removed to facilitate port matching, but no material may be added. (3/2003)
    20. Any transmission oil cooler may be used.
    21. The engine cylinder head(s) may be milled only to that amount specified in the manufacturer's workshop manual. If no amount is specified than a maximum of 0.010 in. may be milled.
    22. Axle/halfshaft and driveshaft retention/location devices may be installed for safety reasons to control the motion of attached shafts upon the failure of a coupling or universal joint. They may serve no other purpose.
    23. Any accessory pulleys and belts of the same type (e.g., V-belt, serpentine) as standard may be used.  This allowance applies to accessory pulleys only (e.g., alternator, water pump, power steering pump, and crankshaft drive pulleys).  It does not allow replacement, modification, or substitution of pulleys, cogs, gears, or belts which are part of cam, layshaft, or ignition drive or timing systems, etc.  Supercharged cars are excluded from this allowance.  This does not permit replacement of integral pulley-damper/balancer assemblies. Alternate pulley materials may be used. Idler pulleys may be used for belt routing in place of items which the rules specifically allow to be removed, such as smog pumps and air conditioning compressors. They may serve no other purpose.  Supercharged cars may not change the effective diameter of any pulley which drives the supercharger. (11/2003)

    14.11 Out-of-Production Cars

    Where a car is out of production and the manufacturer is either out of business, stocks no parts or no longer has a required part, a part of any origin but as similar as possible to the original may be substituted. The entrant must be prepared to show documentary evidence that one of the three circumstances above applies and that the substituted part is as similar as possible under the circumstances.  Substitute parts which provide improvements in performance (e.g. superior gearing, lighter weight, better camshaft profile, etc.) are not permitted under this allowance.

    ...Jerry Mouton || jerry@moutons.org || Last modified 02/22/03