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The Guide to Legal Car Modifications in Wisconsin

The Guide to Legal Car Modifications in Wisconsin ARENA Creative /

If you have a modified vehicle and either live in or plan to move to Wisconsin, you need to know the laws that determine whether your car or truck is street legal. The following regulations govern vehicle modifications in Wisconsin.

Sounds and noise

Wisconsin has regulations in place regarding both the sound emitted from your vehicle’s sound system and that of the muffler.

Sound systems

  • Sound systems cannot be played at levels that are considered excessive in any city, town, neighborhood, county or village. If you are charged with playing music excessively loud two or more times within three years, your vehicle can be impounded.


  • All vehicles must have mufflers that are designed to prevent unreasonably loud or excessive noise.

  • Cutouts, bypasses, and similar devices are not permitted.

  • Modifications that create flame inside or outside the exhaust system are prohibited.

  • Modifications to increase sound levels of the engine over that of the manufacturer are prohibited.

Tip: Always check with local county laws in Wisconsin to make sure you are following any municipal noise ordinances that may be more stringent than state-level laws.

Frame and suspension

Wisconsin has restrictions on modifications to the frame and suspension:

  • 4x4 vehicles that have a Gross Vehicle Weight Rating have a 5-inch suspension lift limit.

  • Shackles can be no longer than two inches longer than stock size for the vehicle.

  • Vehicles with a Gross Vehicle Weight Rating of less than 10,000 pounds cannot have a bumper height exceeding 31 inches.

  • Bumpers must be three inches tall.

  • Vehicle can be no taller than 13 feet 6 inches.

  • Car bumpers can be lifted to within two inches of original factory height.

  • Truck bumpers must be no more than nine inches above factory height.


Wisconsin does not have any engine modification or swap regulations. There are seven counties in which emissions testing is required. Check the Wisconsin DMV website for additional information.

Lighting and windows


  • Two fog lamps are permitted.
  • Two auxiliary lamps are permitted.
  • No more than four lights can be lit at one time.
  • Two backup lamps are permitted with white or amber light.
  • Green lights are only permitted on buses and taxicabs for identification.
  • Red lamps are for authorized vehicles only.

Window tinting

  • Non-reflective tint is permitted on the top of the windshield above the AS-1 line from the manufacturer.

  • Front side windows must permit 50% of light to pass through.

  • Back side and rear window tint must allow over 35% of light to pass through.

  • Side mirrors are required with rear window tint.

Antique/classic car modifications

Wisconsin offers Collector Plates that have no restrictions for daily travel or age of the vehicle.

If you want to make sure the modifications on your vehicle are in compliance with the laws in Wisconsin, YourMechanic can provide the mobile mechanics to help you install the new parts. You can also ask our mechanics what modifications may be best suited to your car using our free online Q&A system, Ask a Mechanic.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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