2008. Spec Miata Class Specifications
9.1.8. SPEC MIATA CLASS
These specifications are part of the SCCA GCR and all automobiles shall conform
to GCR Section 9.
A. PURPOSE AND INTENT
The Spec Miata (SM) class is intended to provide the membership with the
opportunity to compete in low cost, production-based cars with limited
modifications, suitable for racing competition.
The rules are intentionally designed to be more open than the Showroom Stock
class but more restricted than the Improved Touring class.
The vehicle identification number (VIN) shall correspond with the model-year
automobile classified. VIN plates or stampings shall remain in place.
There must be a minimum of two (2) VIN plates or stampings that correspond with
the model year automobile classified.
B. CLASSIFIED CARS AND WEIGHTS
Classified cars and weights are listed on the Spec Miata Specification Table.
Cars are to be weighed with the driver and required ballast. See GCR Section
C. AUTHORIZED MODIFICATIONS
The following items represent the only modifications and safety items permitted
and/or required on Spec Miata automobiles other than safety items as required in
Section 9. No permitted component/modification shall additionally perform a
prohibited function. No updating or backdating of cars, models, specifications,
and/or components thereof shall be permitted except as specifically authorized
in these specifications.
A Shop Manual for the specific make, model, and year of automobile is required
to be in the possession of each entrant. The manual is intended to aid
Scrutineers in identifying parts and the configuration of the automobile.
Overhaul procedures that in the slightest way would increase performance are not
to be utilized; e.g., porting, etc. Blueprinting and balancing are inconsistent
with the philosophy of this class and are not permitted.
All adjustments shall be at the manufacturer’s specification and/or within the
manufacturer’s specified tolerances except as permitted within the SMCS.
Stock replacement parts may be obtained from sources other than the manufacturer
provided they are the exact equivalent of the original parts. The intent of this
rule is to allow the competitor to obtain replacement parts from standard
industry outlets, e.g., auto-parts distributors, rather than from the
manufacturer. It is not intended to allow parts that do not meet all dimensional
and material specifications of new parts from the manufacturer.
The application and/or use of any painting, coating, plating, or impregnating
substance (i.e. anti-friction, thermal barrier, oil shedding coatings, chrome,
anodizing, etc.) to any internal engine surface, transmission, differential,
internal or external surfaces of the exhaust manifold or down-tube, is
a. Induction System
1.All air entering the intake tract shall pass through the
fuel injection air inlet.
2.1.6L cars may replace the stock air box with a cone style
air filter assembly. The air filter element is unrestricted. No ducting or
baffling of air to the air filter is permitted.
3.1.6L cars may open and adjust, but not modify, the OEM
airflow meter. For 1.6L cars, the position of the air flow meter may be moved
provided it remains attached to the unmodified
factory intake tube.
4. 1.8L cars must use the stock air box, but the air filter
element is unrestricted.
5. 1.8L cars shall use an air restrictor. The throttle
restrictor shall be placed between the throttle body and plenum. All intake air
shall pass through the restrictor plate.
Restrictor plates must be the proper size as listed in the Specification Table,
must be from Mazdaspeed Motorsports Development, and must not be modified.
b. Fluid hoses and clamps, oil filters, fuel filters, and belts (fan,
alternator, etc.) may be substituted with others of equivalent OEM
c. Fuel System
1. Unleaded fuel filler trap door and restrictor plate in
filler neck may be removed.
2. Refer to GCR Section 9.3.25 for permitted fuel
specifications and for the required fuel sample acquisition port.
d. Ignition/Electrical System
1.Spark plugs and spark plug wires
may be substituted.
2.Ignition timing is unrestricted
within stock adjustment capability.
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.
e. Exhaust System br />
1. The factory exhaust system beyond the OEM front down pipe may be replaced,
aa. Said replacement system retains the original configuration, e.g. single tube
design, and the tubing diameter is a maximum of 2.25” outside diameter.
b. The pipe may end anywhere after the rear subframe. Forward of the rear
subframe, the pipe must follow the original path of the OEM exhaust system.
c. No expansion chambers. A single muffler may be added.
d. The system meets all event specific sound requirements.
e. A cat replacement tube may be installed. The tube shall not exceed 17.5” in
length and have an outside diameter no greater than 2.375”.
2.Original exhaust system heat shields may be removed. br />
f. Clutch System and Flywheel: All cars shall use either the stock OEM pressure
plate appropriate model year or the ACT pressure plate (Mazdaspeed p/n:
0000-0205401-SS (1.6L cars)
or 0000-0205404-AC (1.8L cars)). The unmodified pressure plate shall be bolted
directly to the appropriate stock, unmodified flywheel. The 94 model year may
utilize the flywheel from
tthe 95-05 model years. Any clutch disk may be used. The minimum weight
(including the pilot bearing) is 17.6 lbs for the 1.6L and 17.1 lbs for the
g. Lubricants may be substituted with any lubricant. Oil additives are
h.The engine block and/or cylinder head may be decked/milled to achieve the
factory specified compression ratio for the correct model year as listed on the
i. Camshafts shall comply with the Official Camshaft Data as supplied by the
SCCA Club Racing Tech Department.
j. Cast iron cylinder liners (sleeves) may be installed to restore damaged or
worn cylinder bores to the original dimension.
2. Cooling System
a. Any radiator may be used, provided it is mounted in the original location,
maintains the same plane as the original core and requires no body or structure
modifications to install. Any br />
openings created by fittng an alternate radiator shall be blocked to prevent air
from entering the engine compartment. The stock cooling fan(s) must be
maintained. At least one functional
sstock OEM cooling fan must be mounted in one of the stock locations.
b. Thermostats may be modified, removed, or replaced.
c. All cars may install the Upper Radiator Seal, p/n NA75-50OK7A
d. A radiator screen of one-fourth (1/4) inch minimum mesh may be added in front
of the radiator and contained within the bodywork. br />
e. The factory air conditioning systems may be removed. Items that serve a dual
purpose, such as the alternator/air conditioning compressor bracket, may not be
f. Engine coolant fluid, coolant/heater hoses and clamps may be substituted.
Heater core may be bypassed. It may not be modified or removed. Heater water
control valve(s) may be added or
3. Transmission/Final Drive
a. Transmission and final drive ratios must remain stock for the year of car.
1999-up cars shall only use the 5 speed transmission and the 4.3 differential
ratio. All cars may use the stock br />
unmodified OEM open differential or one of the approved alternates listed below.
b. 1990 to 1993 Miatas may use the stock, unmodified viscous limited slip
differential or the MAZDASPEED Motorsports Development limited slip
differential, part number #QN10-64A00
(previously TOY1-27-200 & 0000-02- 5501).
c. 1994 and newer cars may use the stock Torsen limited slip differential.
d. The 90-93 Miatas may convert to the 99-05 differential housing and the 4.3
differential gear ratio from the 99-05 model years. This conversion includes the
driveshaft and half-shafts. The
ooriginal 90-93 model rear suspension uprights must be retained.
Suspension modifications are limited to the addition of the MAZDASPEED
Motorsports Development “Spec Miata kit” and those modifications detailed in
a. MAZDASPEED Motorsports Development Spec Miata kit br />
1990-93 1.6 DOHC K-SPEC-M5-SUSP
1994-97 1.8 DOHC K-SPEC-M5-SUS8
1999-up 1.8 DOHC K-SPEC-M5-SUS9
The following is a breakdown of components supplied within these kits.
All parts numbers are MAZDASPEED Motorsports Development parts numbers. No
substitution of parts is allowed. The kits must be used in their entirety.
FFront Bilstein 0000-04-5225-BL
Rear Bilstein 0000-04-5226-BL
2.Springs br />
FFront Eibach ERS 700 lbs/6” 0000-04-9700-06
Rear Eibach ERS 325 lbs/7” 0000-04-9325-07
3. Coil-Over kit
4. Anti-Roll Bars
Eibach kit - front / rear bars 0000-04-5302-EB
Front 24mm Adjustable
Rear 15mm Adjustable
Eibach kit - front / rear bars 0000-04-5303-EB
Front 27mm non-Adjustable
Rear 15mm Adjustable
Eibach kit – front / rear bars 000-04-5304-EB
Front 27mm non-Adjustable br />
Rear 15mm Adjustable
b. All cars shall use unmodified Mazdaspeed bump stop (Part # 0000-04-5993AW).
1999-up cars shall use the bump stops from the Mazdaspeed kit (p/n
0000-04-5993-AW) in conjunction with the 1999-up stock upper mount assembly
consisting of the upper mount (p/n: NC10-28-
340C), the upper mount bushing (p/n: NC1028-775) and the upper mount washer (p/n:
NC10-28-774). All other OEM upper mounting hardware shall be discarded.
c. Subframe braces may be updated to stock 1997 configuration utilizing the
MAZDASPEED Motorsports Development Spec Miata kit.
dd. Anti-roll bar links may be replaced and may be adjustable, but the attachment
points must remain stock. The control arms and specified anti-roll bar may not
be modified. One end of the sway bar(s) may be disconnected as a suspension
tuning aid. The bar must remain in place and be solidly attached to the
suspension on one end.
e. Suspension alignments (camber, caster, toe) are unrestricted within the
limits of the unmodified factory adjustments. Minimum ride height is
unrestricted. br />
f. No relocation or reinforcement of any suspension component or mounting points
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.
i. Towing eyes per GCR Section 9.3.46 are required. Stock towing eyes may be
modified, replaced, or removed but may serve no other purpose.
j. Hubcaps and wheel trim shall be removed.
kk. All chassis/structural/electrical repairs, if performed, shall be in
concurrence with factory procedures, specifications, and dimensions. Unless
specifically authorized by the manufacturer for repair or allowed by these
rules, no reinforcement, i.e., seam welding, material addition, etc., is
l. The front shock tower connector/brace is not permitted on the 1999 and newer
a. Backing plates and dirt shields may be ventilated or removed. br />
b. Brake lines may be replaced with steel lines or Teflon lined metal braided
c. Cars with antilock braking systems must have the system disabled as specified
in GCR 9.3.11.
d. Parking brake mechanisms, and actuating components may be removed.
e. Brake pads and brake fluid are unrestricted
ff. 2001 and newer cars must use the 255mm(F) and 252mm(R) brakes. The larger
brakes 269.5mm(F) and 267.9mm(R) are not permitted.
Any wheel/tire may be used within the following limitations: br />
a. Required rim diameter is fifteen (15) inches. Maximum rim width is seven (7)
inches. Minimum weight of wheel shall be 13 lbs without spacers.
b. Other than the stock 15” Mazda steel wheel, all wheels must be one-piece
metal castings (not multi-piece wheels, bolted, riveted or welded together).
AAll cars shall use the Toyo Proxes RA-1 (205/50R15)
2. Regional Competition br />
AAny DOT approved tire is permitted. Racing, recapped, or regrooved tires are not
allowed. Tire size is unrestricted. The only modifications allowed to tires are
“shaved” or “trued.” Individual regions may require spec tires for regional
races. Supplemental regulations for specific events should be checked. br />
d. 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.
e. 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.
TTo determine compliance, the vehicle should be rolled through a powdered
substance, as raced with driver, in order to indicate the tire tread contact
patch under static conditions.
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 br />
bb. Body repair shall be performed using every reasonable effort to maintain
stock body contours, lips, etc. Any body repair modification having as its
purpose increased clearance is
c. The “R” package Miata chin spoiler is allowed on 1990-1997 cars provided it
is mounted in the OEM location. 1999-up cars may use the OEM chin spoiler for
these cars (99-00 /n: NC10V4-
900F or 01-05 p/n: NO67-V4-900G). Rear spoilers including OEM design are
d. Windshield Clips/Rear Window Straps per GCR Section 9.3.53. are permitted and
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.
f. Body side moldings, rocker panel moldings, and wheel opening trim pieces may
g. The plastic trim on the hood may be removed.
h. Hood and trunk clips are permitted. Stock hood and trunk 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
means of a transparent/alternate vent
window material and duct with no modifications to the bodywork. To improve
driver exit through the window area, the driver vent window and verticle vent
window support may be removed as a
pair. If removed, ducting may be in the passenger side vent window only.
jj. Radio antennas may be removed. Antennas for two-way radios may be added.
8. Driver/Passenger Compartment - Trunk
a. The driver’s seat shall be replaced with a one-piece bucket-type race seat.
All seat mountings shall be reinforced. Factory seat tracks/brackets may be
modified, reinforced, and/or br />
removed to facilitate replacement mountings provided they perform no other
function. The passenger seat must be removed.
b. Any steering wheel, except wood rimmed types, and its required mounting
modifications may be used. Any shift knob may be used.
c. 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 make to mount instruments and
provide for roll cage installation, the remainder of the dash “board” or panel
shall remain intact.
d. Any interior or exterior mirrors may be used.
ee. Carpets, center consoles, cargo bins, seat belts, floor mat, radio system,
headliners, dome lights, grab handles, sun visors 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. br />
f. Two way radios may be used.
g. Spare wheels and tires, jacks and tools shall be removed from the cargo/trunk
area. Spare tire covers and trunk mats and/or trunk carpeting shall be removed.
hh. Modifications may be made to the foot pedals to improve the comfort and
accessibility to the driver. Dead pedal/foot rest and heel stop may be added.
i. If ballast is required to meet the required weight it shall be added as
1. All ballast shall be securely mounted on the passenger
2. Each segment of ballast shall be fastened with a minimum
of two (2) one-half (1/2) inch bolts and positive lock nuts of SAE Grade 5 or
better and shall utilize large diameter, load distributing washers.
3. Holes may be drilled in the passenger floorpan for the
purposes of mounting the ballast and the floorpan may be reinforced for that
j. All cars shall run with both front door windows fully open (down).
a. Steering lock mechanisms shall be removed. See GCR Section 9.3.41. br />
b. An electrical master (“kill”) switch is required. See GCR Section 9.3.33.
c. Installation of a fire extinguisher or fire system is required. See GCR
d. Air bag systems shall be disarmed and may be removed.
ee. In any automobile where allowed removal of upholstery, seat belts, etc.,
creates an opening between the driver/passenger compartment and an exposed gas
tank, or part thereof, including the filler tube, a metal bulkhead which
completely fills such openings