WhatClassAmIAutocross Classing Guide

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Class my car

Pick your car, check what you've changed. Green = fine in Street. Red = that item moves you — and we'll show you where.

Fast lane · describe your car in plain English

This only fills in the pickers — your class is always computed by the rules engine, never by the AI.

1 · Your car

+295 more — keep typing to narrow.

2 · Your modifications

Sizes & drivetrain (for exact class limits)

Tire width (mm)Wheel width (in)DrivetrainMid-engine

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Tires & Wheels

Performance tires (UTQG 200+ treadwear)UTQG 200+ treadwear, min 7/32" molded tread depth, and listed in the Tire Guide (§13.3.A). Must fit allowable wheels without fender modification.
Aftermarket wheels (stock width, ±1" diameter)Same width as standard, offset within ±7.00mm of stock, diameter ±1" (§13.4). Spacers count as part of the wheel.
Wider wheels / any diameter (width per class)Width limits enforced per class via the wheel-width input: EST/AWD-AST/CST 7.5", DST AWD 8.0", most 2WD 9.0", BST 11.0", SST unlimited.
Wider 200TW tires than stock allows (width per class)Section-width limits enforced per class via the tire-width input: 225-315mm by class and drivetrain; SST unlimited.
R-comp / DOT tires below 200TW (e.g. Hoosier A7)
Wheels — any size, any width

Suspension

Aftermarket shocks/struts (stock spring rates & mounting)Street shock rules are more restrictive than ST — verify §13.5 details (count, adjustability limits).
Aftermarket anti-roll bar — ONE end only (front OR rear)
Alignment within factory adjustment range
Coilovers / lowering springs
Anti-roll bars on BOTH ends
Camber bolts / camber plates
Suspension/steering bushings (non-OE)
Strut bar / tie bar (2-point bolt-on)2-point bars freely; 3-point substitution rules apply (§14.2.G).

Engine & Drivetrain

Drop-in air filter elementFilter element only — no 'cold air' intake kits in Street.
Cat-back or axle-back exhaust
Cold air intake (to throttle body / turbo inlet)
ECU reflash / tuneReprogrammed PCM/ECU OR changed fuel pressure regulator.
Exhaust headers / high-flow cats
Limited-slip differential (one)Not allowed in EST except factory viscous units; AWD may replace one diff (SST–DST); GST 2WD only (§14.10.K).
Engine / transmission mounts
Radiator / fan upgradeCore dimensions >= standard, OE mounts, capacity/weight >= standard (§14.10.L).
Clutch / lightweight flywheelFULL PREP only — any metal clutch/flywheel (§15.10.O).
Standalone ECU / fuel system / ignition replacementFuel injection systems and carburetors unrestricted (§15.10).
Emissions equipment removed (cat delete, etc.)
Engine or drivetrain swap
Added turbo/supercharger (not factory)Engine/drivetrain systems broadly unrestricted in SM with listed limitations — verify §16.1 details for your combination.

Brakes

Brake pads / shoes
Big brake kit / brake linesRotors equal/larger & ferrous; calipers bolt to standard locations, piston count >= standard (§14.6.A/E).
Brake cooling ducts

Body & Aero

Small spoiler / splitterFULL PREP only; front spoiler/splitter below bumper, no side skirts (§15.2.I).
Aero wingRear deck/hatch behind rear axle centerline, max 8 sq ft total, 2 elements (§16.1.K).
Fenders modified/replaced for tire clearanceFULL PREP only — fenders/bumpers modified for tire clearance; complete replacement/flares prohibited (§15.2.A).

Interior & Electrical

Battery replacement (with hold-down)Replacement + supplemental hold-down hardware (§13.9.E). Relocation behind seats is an ST allowance (§14.9).
Aftermarket front seat(s)Seat + hardware must weigh >= 25 lb, fully upholstered, OE mounting holes (§14.2.B).
Aftermarket steering wheelReplacement for airbag wheel must weigh at least as much as standard assembly (§14.2.D).
Driver seat belt / harnessRestraints per §3.3.1; seats may not be cut; 2-point harness bar allowed (§13.2.G).
Rear seats removedFront seatbacks must remain covered when rear seats are removed (§16.1).
Radio/stereo removedFULL PREP only — Limited Prep SP cars keep the radio (§15.2.N).

3 · Your class

Select a car to see its class.

Unofficial tool — not affiliated with or endorsed by the SCCA®. Always verify against the current SCCA Solo Rules. Classing questions can be submitted to the Solo Events Board.

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