[SCCA] Solo II Stock Class Rules

This is an unofficial transcription of Section 13 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.


  • 13.1 Authorized Modifications
  • 13.2 Bodywork
  • 13.3 Tires
  • 13.4 Wheels
  • 13.5 Shock Absorbers
  • 13.6 Brakes
  • 13.7 Anti Roll (Sway) Bars
  • 13.8 Suspension
  • 13.9 Electrical System
  • 13.10 Engine and Drive Train


    Cars running in Stock 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. Car models not specifically listed in any Stock Category class must have been produced, and must have met the above requirements and must have been sold through normal U.S. dealerships, in quantities of at least 1,000 in a 12-month period to be entered in the Stock Category.

    Except for modifications authorized below, Stock Category cars must be run as specified by the factory with only standard equipment as defined by these Rules. This requirement refers not just to individual parts, but to combinations thereof which which would have been ordered together on a specific car. Any other modifications or equipment will place the car in Street Prepared, Prepared or Modified Categories as appropriate.

    Option package conversions may be performed between specific vehicles of a particular make and model, but only between configurations from within a particular model year. Such conversions must be totally complete and the resultant car must meet all requirements of this section.  Alternate parts listed in a factory parts manual are not authorized unless their use is specifically referenced in the factory service manual or in a service bulletin for the specific model.

    The entrant has the burden of proving that his car conforms to these Rules by his owner's manual, manufacturer's shop manual, manufacturer's catalogs or other official manufacturer's documentation, which must be in the possession of the entrant at the event if ever available to the consumer from the manufacturer. At a minimum, the competitor must be in possession of the manufacturer's workshop manual. All manuals, catalogs and official documentation must be for non-competition purposes. If protested competitor possess the documentation required by this Section, but that documentation does not include sufficient information on the protested item, the burden shifts to the protesting competitor to prove the item illegal. Failure to provide appropriate manufacturer's documentation regarding vehicle specifications will result in disqualification.

    (OEM = Original Equipment Manufacturer's -- ed.)

    Alternate components which are normally expendable and considered replacement parts (e.g., engine and wheel bearings, seals, gaskets, etc.) may be used provided they are the same type and size as the standard parts and used in the same location. This does not include camshafts, differential covers, or ring-and-pinion sets.

    Hardware items (nuts, bolts, etc.) may be replaced by similar items of unrestricted origin. These allowances are strictly to allow components to be replaced from alternate sources other than the original manufacturer. They should not be construed as an allowance to replace components with those which could be considered a 'higher performance' alternative. Safety wire, threadlocker compounds, and locking nuts are permitted.  Parts available as replacements through the dealers parts department, the factory, or any other source which do not meet standard part specifications (e.g., hardness, size, etc.) are not legal in Stock Category, except as specifically provided elsewhere in these rules.

    Cars listed as eligible in and prepared to the current national Showroom Stock Club Racing rules are permitted to compete in their respective Solo II Stock Classes. This does not include Showroom Stock cars with installations of post-factory "performance packages" otherwise known as "trunk kits".  Neither Showroom Stock nor Solo II Stock cars are permitted to interchange preparation rules.  Showroom Stock cars may use tires which are eligible under current SS rules, even if they are not eligible in Stock.

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

    13.1 Authorized Modifications

    If a modification is not specifically authorized in this or previous sections of these Rules it is not allowed. It is not permitted to use illegal parts even if they have been set to stock specifications.

    Refer to Appendix F for past clarifications of these rules.

    13.2 Bodywork

    1. Accessories, gauges, indicators, lights and other appearance, comfort and convenience modifications which have no effect on performance and/or handling and do not materially reduce the weight of the car are permitted. This does not allow driver's seat substitutions or the removal of "tow hooks", a.k.a. "tie down loops". Delayed shutdown devices such as the "Turbo Timer", which perform no function while the car is in motion, are permitted.  This does permit the installation of an additional mirror (e.g. a "Wink"), but does not allow the removal of the original mirror.
    2. Hood straps or fasteners may be added.
    3. Any fuel tank cap may be used.
    4. Windshields may be folded (but not removed) provided the required mechanism is standard equipment.
    5. Alternate steering wheels are allowed, provided the outside diameter is not changed by more than one inch from the standard size.  Steering wheels with an integral airbag may not be changed.
    6. Spare tires, tools and jacks may be removed.
    7. Roll bars and roll cages may be added (see Appendix C). It is strongly recommended that they be constructed according to Section 18 of the current GCR. Roll bars may be welded. Roll cages must be bolted, not welded, into the automobile and within the driver/passenger compartment. A roll cage has more than four attachment points to the body or frame, or has bracing both fore and aft of the main hoop.
    8. Driver restraints as outlined in Section 3.3.1 are allowed. Seats may not be cut to allow for the installation of alternate seat belts or harnesses. Passive restraint systems may not be removed. A horizontal "harness bar" may be used as part of the installation hardware for allowed driver restraints.  It may serve no other purpose (e.g., structural enhancement).
    9. Cars may add one rear trailer hitch. The resulting weight addition is allowed. The hitch may serve no other purpose. Factory tie downs may be removed to facilitate hitch installation.
    10. Tow bar brackets may be installed but may serve no other purpose.
    11. Any item that can not be held permanently in place by factory installed fasteners may be removed.

    13.3 Tires

    Any tire which is O.E.M. on a car eligible for Stock Category may be used. Non-O.E.M. tires must meet the following requirements to be eligible for use in Stock category:
    1. The tire must not appear on the following list, which may be altered at any time by the SEB upon notification of membership.
    2. No tire models are currently listed.

    3. No tire models will be approved for competition during the rest of the year after April 30 of each calendar year. Each eligible tire model must meet all requirements of section 13.3 by April 30, and must continue to meet them thereafter. A tire model will normally be determined by the designation in the Tire Guide. However, any of the following changes or similar changes (as determined by the SEB) will also be considered to represent a new model for eligibility purposes, even if the designation does not change: Change of tread pattern at either full or partial tread depth; characterization by the manufacturer or distributor of a tire as "new" after April 30.

    4. Discontinued model tires already produced will continue to be eligible for Solo II competition in Stock and Street Prepared categories.  This follows years of precedence on eligibility for discontinued tire models.

      If a manufacturer reintroduces a tire model which was previously discontinued, that tire will be considered a new model.  Therefore, it will have to meet the rules specified in SIIR Section 13.3 including the April 30 introduction date.|

    5. The model of tire must be listed in a current or previous two years of the Tire Guide and Tread Design Guide, or otherwise be approved by the SEB. The tire model must have Department of Transportation approval.
    6. Within each tire model, the sizes which are available must be equally available to all competitors. Tire model variations differing from standard specification, delivered only on a limited basis, or only to selected competitors, may not be used.
    7. No racing tire or recap (on any casing) may be used.
    8. Each tire model must be sold in at least four diameters, with a total of at least six sizes.
    9. Tire must fit the allowable wheels and fender wells without modification.
    10. Each tire must have non-zero measurable tread depth (i.e., points where it is possible to obtain positive measurement values) as described in Section 3.3.D. Tires may not have cord visible at any time during competition.

    13.4 Wheels

    Any type wheel may be used provided it complies with the following: it is the same width and diameter as standard, and as installed (including wheel spacers if applicable) it does not have an offset more than +/- 0.25 inch from a standard wheel for the car. The resultant change in track dimensions is allowed. Vehicles originally equipped only with 12 inch diameter wheels, may use 13 inch diameter wheels of the same width as standard and offset within +/- 0.25 inch of standard.

    Wheel spacers are permitted, provided the resultant combination complies with the offset requirements of this section. Wheel studs lug nuts, and/or bolt length may be changed.

    Vehicles equipped with rims having metric specifications may use alternate rims as determined by using the following procedure.

    Diameter: converting the metric measurement to inches and using the nearest smaller inch diameter rim.

    Width: converting the metric measurement to inches and using the nearest smaller 1/2-inch width rim. Offset and track must still comply with the requirements of this section.

    13.5 Shock Absorbers

    1. The make of shock absorber may be substituted providing that the number, type, (e.g., tube, lever, etc.) system of attachment and attachment points are not altered, except as noted below. The interchange of gas and hydraulic shock absorbers is permitted. The following restrictions apply:
      1. No more than two separate external shock damping adjustment controls.  Gas pressure adjustment is not considered a damping adjustment.
      2. Suspension geometry and alignment capability, not including ride height, may not be altered by the substitution of alternate shock absorbers.
      3. Adjustable spring perches are allowed, but the spring load-bearing surface must be in the same location relative to the shock mounting points as on the standard part.  Shims may be used to achieve compliance.
      4. The fully extended length must be within plus or minus one inch of the dimension of the standard part. 
      5. Electronically controlled shocks may not be used on vehicles not originally equipped with such units. Vehicles originally equipped with electronically controlled shocks may use the standard parts or non-electronically controlled alternative shocks subject to all requirements of 13.5.  Non standard electronically controlled active shocks are not allowed.
    2. The mounting hardware shall be of the original type.  The use of any shock absorber bushing material, including metal, is permitted.  This does not permit the use of an offset shock absorber bushing.  The bushing attaching the end of the strut to the body or frame on a strut type suspension is a suspension bushing, not a shock absorber bushing. Suspension bushings, including but not limited to those which carry the weight of the car and determine ride height, may not be replaced with bushings of a different material or dimension.
    3. To facilitate the installation of commonly available aftermarket shock absorbers, struts, or strut inserts whose shaft is larger than the center hole of an upper mount assembly, that hole may be enlarged by the minimum amount necessary to accommodate the shock shaft size, provided the following restrictions are met:
      1. the enlarged hole must remain concentric with that of the original configuration;
      2. the enlargement of the hole does not require modification of a bearing (as opposed to a washer, plate, or sleeve);
      3. neither the hole enlargement nor the location of the shock shaft changes any alignment parameter.
    4. A suspension bump stop is considered to be performing the function of a spring. Therefore, the compressed length of the shock at the initial point of contact with the bump stop may not be increased from the standard part, although the bump stop may be shortened for the purpose of installing non-standard shocks.  Bump Stops installed externally and concentric with the shaft of a shock may be drilled out to fit a larger diameter shock shaft.   Bump Stops may be substituted for the purpose of installing non-standard shock absorbers.

    13.6 Brakes

    1. The make and material of brake linings may be changed.
    2. Substitution of clutch and brake hydraulic lines with solid metal or braided metal is allowed on all cars manufactured before model year 1992.
    3. Alternate brake bleeder fittings such as "Speedbleeders" are permitted  They may serve no other purpose.

    13.7 Anti Roll (Sway) Bars

    1. Front anti-roll (sway) bars:
      2. Substitution, addition or removal of any front anti-roll bars is permitted.
      3. Substitution, addition or removal of anti-roll bars may serve no other purpose than that of an anti-roll bar.
      4. The use of any bushing material is permitted.
      5. No modification to the body, frame or other components to accommodate anti-roll bar addition or substitution is allowed, except for the drilling of holes for mounting bolts. Non-standard lateral members which connect between the brackets for the bar are not permitted.
    2. Rear anti-roll (sway) bars:
      2. May not be removed, replaced, or modified in any way.

    13.8 Suspension

    Standard, as defined herein, suspension springs must be used. They may not be cut, shortened or collapsed. Cars with swing axle suspension may be lowered sufficiently to achieve no more than two degrees of negative camber at rest, and may use a camber compensator.

    Both the front and rear suspension may be adjusted through their designed range of adjustment by use of factory adjustment arrangements or by taking advantage of inherent manufacturing tolerances. However, no suspension part may be modified for the purpose of adjustment unless such modification is specifically authorized by the factory shop manual for non-competition purposes.

    Replacement control arms for vehicles having integral bushing/arm assemblies must be standard factory parts as per Sections 12.4 and 13.0. This encompasses both alignment and ride height parameters, if such adjustments are provided by the stock components and specified by the factory as normal methods of adjustment.

    If authorized by the manufacturer, the use of shims, special bolts, removal of material to enlarge mounting holes, and similar methods are allowed and the resulting alignment settings are permitted even if outside the normal specification or range of specifications recommended by the manufacturer. If enlarging mounting holes is specifically authorized but no material removal limits are specified, material removal is restricted to the amount necessary to achieve the maximum factory alignment specification.

    13.9 Electrical System

    1. The make of spark plugs, points, ignition coil and high tension wires is unrestricted including spark plug wires having an in-line capacitor .
    2. On cars made prior to January 1, 1968, any ignition system using a standard distributor without modification may be used.
    3. Ignition settings may not be adjusted outside factory specifications.
    4. No changes are permitted to electronic engine management systems or their programming.

    13.10 Engine and Drive Train

    1. The engine air filter element may be removed or replaced. A replacement element which is taller than standard may not be used to hold the air cleaner cover open. No other components of the air induction system may be removed, replaced or modified.
    2. Engines may be rebored to the manufacturer's first standard overbore, not to exceed 0.020". Sleeving is allowed to repair to the standard bore. Only OEM-type standard or first overbore pistons of the same configuration and of the same or greater weights are permitted. No interchange between cast and forged pistons is allowed.
    3. Rotating and reciprocating parts may not be balanced.
    4. Port matching is not allowed.
    5. Any part of the exhaust system beyond (downstream from) the header/manifold or catalytic converter, if so equipped, may be substituted provided the system meets the requirements of 3.5. Stainless steel heat exchangers are permitted only if the physical dimensions and configuration remain unchanged. Modifications of any type, including additions to or removal of, the catalytic converters, thermal reactors, or any other pollution control devices in the exhaust system are not allowed and the system must be operable. Replacement catalytic converters must be OEM if the vehicle has not exceeded the 5-year/50,000 mile warranty period as mandated by the EPA. Converters must be of the same type and size and used in the same location as the original equipment converter(s). This does not allow for a high performance unit. If the vehicle has exceeded the 5 year/50,000 mile warranty period, replacement catalytic converters must be OEM-type as per Section 13.
    6. Any oil filter may be added if not originally equipped. Canister-type oil filters may be replaced with a spin-on type filter using a minimum amount of hardware and connecting lines.
    7. The installation of water expansion tanks is allowed. The installation of oil catch tanks is allowed provided the PCV system is not altered.
    8. A scattershield may be added. This does not permit bell housing substitutions.
    9. Thermostats may be added or substituted. A thermostat is a device which controls the passage of water.
    10. Silicone replacement hoses are permitted as alternate components, provided they meet the requirements of section 13.0 with regard to size, shape, location, and performance equivalence.
    11. A device for locking out reverse gear may be used.
    12. Limited-slip differential, transmission and differential ratios, clutch mechanisms, and carburetion, fuel injection or supercharger induction systems must be standard as herein defined.
    13. Any oil or grease, including synthetic, is permitted.
    14. Valve seats and guides in older engines originally designed for leaded fuel may be only substituted with alternate components if the dimensions of are the same as those of the standard components.

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