Car Class Calculator

This calculator helps you determine your class eligibility and modification points based on your modifications.

Chassis

Gen. 2 cars adhering to Stock Class rules can participate in Stock Class but will take a time handicap. Please refer to the current rules for details.

Single choice

Gen. 1 (2013–2020 model years) 0.0

Gen. 2 (2022+ model years) 2.0

Tires

For Stock and Street Class, heavy tire restrictions apply (see rules for details). Any tire not on this list is automatically 6pts.

Single choice

17" GT Radial SX2 / HPY, 17" Michelin Primacy HP / 4 -1.0

PS4, V601 0.0

18" GT Radial SX2, GT Radial SX2 RS 1.0

B-TR, ECF, ECS, ZII SS, ZIII, RT615K+, 595RS-RR, F1S3, RS-4, V730, VR-1, PS4S, Cup 2 (180TW) / Connect, NS-2R, SUR4, NT01, NT05, R888, AD08R, AD09 2.0

Super tires: Rival S, RE71R, RE71RS, RT660, F1S3R, TrackAttack Pro, RC-1, VR2, AR-1, CR-1, SUR4G, A052 3.0

Treadwear 40–99 5.0

Racing slicks or any tire not listed above 6.0

Suspension

Free Modifications:

Any alignment bolt/kit
Any altered suspension mounting points and suspension lengths
Any bolt-on chassis bracing
Any spherical bushings, including strut top mounts
Any sway bars
Any wheel spacers

Single choice

Unmodified OE or OE-Replacement dampers with OE springs and bump stops 0.0

Unmodified OE or OE-Replacement dampers with aftermarket/modified springs and/or bump stops 0.5

Any other dampers without remote reservoirs with any springs and bump stops 1.0

Any other dampers with remote reservoirs with any springs and bump stops 1.5

Engine: Mechanical & Drivetrain

Free Modifications:

Any cat-back exhaust
Any drop-in replacement air filter for OE intake
Any pump gasoline (including blending high-octane pump gasoline)
Any radiator, oil cooler, oil catch can, oil pan baffle, and/or modified sump
Any transmission cooling or diff cooling system
Gen. 2 charcoal airbox filter removal
Removal of intake resonators

Multiple choices

Aftermarket intake, header, front-pipe, overpipe, and/or any removal of OE catalytic converter 0.5

Lighter-than-OE rotational inertia flywheel, clutch, and/or driveshaft 0.5

Aftermarket limited slip differential 0.5

Aftermarket transmission 1.0

Forced induction 4.5

FA20 to FA24 engine swap 2.0

Any other engine swap (contact Rules Board for individual classification) 8.0

Engine: Tuning

Octane ratings below use (RON+MON)/2 or AKI. This is the octane number displayed at the pump in the US.

Single choice

OEM Tune 0.0

Naturally aspirated engine tune for 93 octane gasoline or lower 0.5

Naturally aspirated engine tune for >93 octane gasoline or >15% ethanol content 1.5

Forced induction engine tune for 93 octane gasoline or lower 0.5

Forced induction engine tune for >93 octane gasoline or >15% ethanol content 2.5

Aero: Splitters/Lips

Single choice

No front aero modifications 0.0

Any device extending up to 50 mm in any direction from the bottom leading edge of the bumper (including STI lip and TRD lip) 0.0

Any device extending up to 75 mm in any direction from the bottom leading edge of the bumper 1.0

Any device extending up to 125 mm in any direction from the bottom leading edge of the bumper 1.5

Any device extending greater than 125 mm in any direction from the bottom leading edge of the bumper 3.0

Aero: Wings/Spoilers

Single choice

No rear aero modifications 0.0

OE rear spoiler, OE wing (except Gen. 1 BRZ tS wing), or any aftermarket spoiler less than 60 mm in height 0.0

Aftermarket rear spoiler greater than 60 mm in height 0.5

SARD LSR, Gen. 1 BRZ tS wing, or any wing with maximum width of 1400 mm, maximum stand height of 200 mm, maximum chord length of 200 mm, and no added gurney flap 1.0

APR GTC-200, Voltex Type 12, Voltex Type 1S, or any wing with maximum width of 1460 mm, maximum stand height of 245 mm, and maximum chord length of 250 mm 1.5

Any wing wider than 1460 mm, higher than 245 mm, or with a chord length greater than 250 mm 2.0

Aero: Other

Free Modifications:

Rear diffuser between the rear axle and the rear trailing edge of the bumper
Rear spats
Side skirts

Multiple choices

Canards, dive planes, hood vents, fender vents, and/or vertical deviations on splitters 0.5

Any underbody aero modifications between the front and rear axles and/or rear diffuser extending backward beyond the rear bumper trailing edge 0.5

Weight reduction

Free Modifications:

Any lightweight battery

Multiple choices

Removal of any interior trim pieces or seating not required for installation of a roll cage 1.0

Safety

Free Modifications:

Any brake fluid, brake pads, brake rotors, brake ducting, and/or big brake kit (BBK)
Any in-cabin safety equipment
Any lug nuts and wheel studs

Points	-1
Class	Stock

Chassis

Tires

Suspension

Engine: Mechanical & Drivetrain

Engine: Tuning

Aero: Splitters/Lips

Aero: Wings/Spoilers

Aero: Other

Weight reduction

Safety

Summary