Purpose and Intent: The Spec Miata (SM) class is intended to provide the membership with the opportunity to compete in low cost cars with limited modifications, suitable for racing competition. It is intended to encourage low cost, entry level, production car based competition in SCCA. Further, the rules are intentionally designed to be more conservative than the Improved touring class, but with equivalent safety standards. The Spec Miata class will be reviewed on a yearly basis for participation. If the class participation drops below a reasonable level, the cars will be assimilated into the appropriate Improved Touring class. These rules are intended to Supplement those of the Showroom Stock Category Specifications (SSCS). The Spec Miata class shall strictly follow the SSCS except f0r modifications permitted by these rules. Unless specifically mentioned or approved in these rules, no additional modifications may be made. A. Classified Cars and Weights: 1.1990 – 1993 Mazda Miata 1600cc at 2300 pounds. 2.1994 – 1997 Mazda Miata 1800cc at 2400 pounds. Cars are to be weighed with the driver. B. Authorized Modifications The following items represent the only modifications and safety items permitted and/or required on Spec Miata automobiles beyond those of the SSCS. No permitted component/modification shall additionally perform a prohibited function. 1. Engine Modifications a. Induction System 1. All air entering the intake tract shall pass through the fuel injection air inlet. 2.1600cc Cars may replace the stock air box with a cone type air filter assembly. The air filter element is unrestricted. 1800cc cars must use the stock air box, but air filter element is unrestricted. 3. 1800cc cars shall use a restrictor in the fuel injection system. The throttle restrictor shall be placed between the throttle body and the plenum and shall be a 0.060" flat steel or aluminum plate with the specified orifice. No air shall bypass the throttle restrictor. 1994-1995 47mm restrictor 1996-1997 45mm restrictor b. Fuel System 1. Unleaded fuel filter trap door and restrictor plate in filler neck may be removed. c. Ignition/Electrical System 1. Ignition wires may be substituted. 2. Ignition timing is unrestricted. 3. Batteries may be replaced with those of an alternate manufacturer, provided they are of similar amp-hour capacity, size, and weight and are fitted in the standard location. Additional battery hold-down devices may be used, and are strongly recommended. d. Exhaust System 1. The factory exhaust system beyond the OEM front down pipe may be replaced, provided: a. Said replacement system retains the original configuration, e.g. single tube design, and the tubing diameter is a maximum of 2.25". b. The system shall exit behind the rear sub frame. c. No expansion chambers. A single muffler may be added. d. The system meets all event specific sound requirements (see GCR Section 12) e. Clutch System 1. Any clutch disc and pressure plate of stock diameter may be used, provided that they shall be bolted directly to the unmodified stock flywheel. The addition of an external scattershield per GCR 17.24 is permitted and recommended. 2. Cooling System a. Any radiator may be used, provided it is mounted in the original location, and maintains the same plane as the original core and requires no body or structure modifications to install. b. Thermostats may be modified, removed, or replaced. 3. Transmission/Final Drive a. Transmission and final drive ratios must remain stock for the year of car. b. 1990 to 1993 Miatas may use the stock, unmodified viscous limited slip differential or the MAZDASPEED Motorsports Development limited slip differential, part number #QN10-64-AOO (previously TOY1-27-200 & 0000-02-5501). c. 1994 to 1997 Miatas may only use the stock Torsen limited slip differential. 4. Chassis Chassis modifications are limited to the addition of the MAZDASPEED Motorsports Development "Spec Miata kit" and those modifications detailed in this area. a. MAZDASPEED Motorsports Development Spec Miata Kit 1990-93 1.6 DOHC K-SPEC-M5-SUSP 1994-97 1.8 DOHC K-SPEC-M5-SUS8 The following is a breakdown of the components supplied within these kits. All part numbers are MAZDASPEED Motorsports Development part numbers. No substitution of parts is allowed. The kits must be used in their entirety. 1. Shocks Front:Bilstein 0000-04-5225-BL Rear: Bilstein 0000-04-5226-BL 2. Springs Front: Eibach ERS 700 lbs./ 6" 0000-04-9700-06 Rear Eibach ERS 325 lbs./ 7" 0000-04-9325-07 3. Coil-Over kit Front/Rear 0000-04-5402AW 4. Anti-Roll Bars K-SPEC-M5-SUSP Eibach Kit - front/rear bars 0000-04-5302-EB Front: 24mm adjustable Rear: 15mm adjustable K-SPEC-M5-SUS8 Eibach Kit- front/rear bars 0000-04-5303-EB Front: 27mm non-adjustable b. Cars registered prior to 1/1/2003 may weld a 63.5 mm centering ring to the top shock mount and turn the stock length bump stop (part# NAO1-28-111) to an outside diameter of 58mm. c. Sub frame braces may be updated to stock 1997 configuration utilizing the MAZDASPEED Motorsports Development Spec Miata kit. d. Anti-roll bar links may be replaced and/or adjustable, but the attachment points must remain stock. The control arms and specified anti-roll bar may not be modified. e. Cars may decamber wheels by the use of factory means to a maximum of two (2) degrees negative in the front, and two and one half (2.5) degrees negative in the rear. f. No other relocation or reinforcement of any suspension component or mounting point is permitted. g. Hardware items (nuts & bolts) may be replaced by similar items performing the same fastening function(s). h. Manual or power steering racks may be used. Power steering racks may be converted to manual by removing all power steering components. 5. Brakes a. Backing plates and dirt shields may be ventilated or removed b. Brake lines may be replaced with steel lines or Teflon lined metal braded hose. Cars with anti-lock braking systems must have the system disabled as specified in GCE 11.2.1.E. c. Parking brakes, mechanisms, and actuating components may be removed. 6. Wheel/Tires a. Any wheel/tire may be used within the following limitations: 1. Required rim diameter is fifteen (15) inches. Maximum rim width is seven (7) inches. Minimum weight of wheel shall be 13 lbs without spacers. 2. Knockoff/quick change type wheels are prohibited. Wheels must be made of metal. 3. Any DOT approved tire is permitted. Racing, recapped, or regrooved tires are not allowed. Tire size is unrestricted. The only modifications allowed to tires are having treads “shaved” or “trued”. Individual regions may require spec tires. Supplemental regulations for specific events should be checked. Approved tire list: Toyo Proxes RA1 Kumho Victoracer V700 Hankook Ventus Z211 Hoosier SM In the event of rain conditions, tire choice will be free.. 4. Track may be changed to accommodate larger tires, provided that there is safe tire/fender/chassis clearance under all conditions of steer, bump, and rebound. Aftermarket wheel studs, lug nuts, and wheel spacers are permitted. 5. Tire tread (that portion of the tire that contacts the ground under static conditions) shall not protrude beyond the fender opening when viewed from the top perpendicular to the ground. To determine compliance, the vehicle should be rolled through a powdered substance, as raced with the driver, in order to indicate the tire tread contact patch under static conditions. 7. Body/Structure a. Fenders and wheel openings shall remain unmodified. It is permitted to roll under or flatten any interior lip on the wheel opening for tire clearance. Non-metallic inner fender liners may be removed. b. The "R" package Miata chin spoiler is allowed provided it is mounted in the location intended by the factory. c. Minimum ride height is unrestricted, but no part of the car, except for the exhaust system and the suspension components, shall be lower than the lowest part of the wheel rims. d. Windshield clips per the GCR section 17.33 are permitted and recommended. e. Convertible tops and attaching hardware shall be completely removed. Cars may compete with the Mazda factory detachable hard top in place (latches shall be replaced with positive fasteners), but it is not mandatory. When no top is used, driver shall wear arm restraints, and the cage will meet the helmet clearance rule. See GCR 18.3.1 for additional information. f. Body side moldings, rocker panel moldings, and wheel opening trim pieces may be removed. g. Hood inner plastic liner may be removed. h. Hood clips are permitted. Stock hood latches may be disabled or removed. i. Ducting may be added to provide fresh air to the driver compartment. This ducting shall be located in the driver and/or passenger vent window area by a means of transparent/alternate vent window material and duct with no modifications to the bodywork. 8. Driver/Passenger Compartment/Trunk a. Any steering wheel except wood rimmed types may be used. Any shift knob may be used. b. Gauges and instruments may be added, replaced, or removed. They may be installed in the original instrument(s) location using a mounting plate(s), or any other location using a secure method of attachment. Other than modifications made to mount instruments and provide for roll cage installation, the remainder of the dash "board" or panel shall remain intact. c. Any interior or exterior mirrors may be used. d. Front passenger seat, sun visors, seat belts and their attaching hardware and bracketry may be removed e. Carpets, center consoles, cargo bins, driver’s seat belt, floor mat, radio system, headliners, dome lights, grab handles and their insulating and attaching materials may be removed. Other than to provide for the installation of required safety equipment or other authorized modifications, no other driver/passenger compartment alterations or gutting are permitted. f. The driver’s door window glass, window operating mechanism, and inside door latch/lock operating mechanism may be removed and the inner door structural panel may be modified but not removed. The stock side impact beam, if equipped, and the outside door latch/lock operating mechanism shall not be removed or modified. This gutting of the door shall only be made to the driver’s door and shall only be made if roll cage incorporates NASCAR-style side protection extending into the door. g. Any removable covers used to cover spare tires, tools, bins, etc., may be removed along with attaching hardware and bracketry. Carpets, mats, and their insulating or attaching materials may be removed from the floor and recesses of the cargo/trunk/spare tire area. h. Dead pedal/ footrest and heel stop may be added. i. Ballast up to 100lb maximum may be located in the front passenger footwall area aft of the firewall and any footwall angle, and forward of the passenger seat. Installation shall be per SSCS. 9. Safety a. Roll cages shall meet all requirements of GCR Section 18., requirements for Showroom Stock cage configuration, tubing size, and material. 1. Regardless of car weight, all Spec Miata autos may be constructed to the requirements for a 2095-pound car. b. Steering lock mechanisms shall be removed. c. An electrical master ("kill") switch is required. See GCR section 17.27 for requirements.

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