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The Guide to Legal Car Modifications in Colorado

The Guide to Legal Car Modifications in Colorado ARENA Creative /

Whether you currently live in Colorado and want to modify your car or you are moving to the area and want to ensure your vehicle is street legal, you need to know the laws and regulations throughout the state. Below you will find out what you need to know to make sure your vehicle is legal on Colorado roadways.

Sounds and noise

Your sound system and muffler must meet certain requirements in Colorado in order to avoid fines.

Sounds system

Colorado regulations limit the decibel levels in specific areas. These include:

  • Residential - 55 decibels between 7 AM and 7 PM, 50 decibels between 7 PM and 7 AM

  • Commercial - 60 decibels between 7 AM and 7 PM, 55 decibels between 7 PM and 7 AM


Colorado muffler modification laws include:

  • Vehicles with a gross vehicle weight over 6,000 pounds and produced prior to 1973 can’t produce noise that exceeds 88 decibels at 35 MPH or less or 90 decibels between 35 and 55 MPH.

  • Vehicles with a gross vehicle weight over 6,000 pounds and produced after January 1, 1973 can’t produce noise that exceeds 86 decibels at 35 MPH or less or 90 decibels between 35 and 55 MPH.

  • All vehicles must have a working muffler.

  • Bypasses and cutouts are not permitted.

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

Frame and suspension

Colorado frame and suspension laws include:

  • Suspension modifications cannot alter the type that was originally used by the manufacturer.
  • Vehicles can’t exceed 13 feet in height.


Colorado has regulations regarding engine modifications as well:

  • Engine swaps must be done with engines that are the same year or newer.

  • Gasoline engines that are over three model years old are required to pass emissions tests.

Lighting and windows


  • Vehicles can have no more than two spot lamps.

  • Vehicles can have no more than two fog lamps.

  • One running board courtesy lamp is permitted per side in white or amber.

  • No more than four lamps greater than 300 candlepower can be lit at a single time on the highway.

Window tinting

  • Non-reflective tint is allowed on the top four inches of the front windshield.
  • Front side and back side windows must allow over 27% of the light through.
  • Rear window must allow over 27% of light through.
  • Mirrored or metallic tint is not permitted.
  • Amber or red tint is not permitted.
  • Two side mirrors are required if the back window is tinted.

Antique/classic car modifications

Colorado only requires that antique, classic and custom-built vehicles be registered at your local county DMV location.

If you’re considering modifying your car to be within the laws in Colorado, 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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