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The Guide to Legal Car Modifications in Illinois

The Guide to Legal Car Modifications in Illinois ARENA Creative /

Whether you want to modify your vehicle while living in Illinois, or you are moving to the state with a modified vehicle, you need to know the laws to ensure you are street legal. The following are some of the requirements for vehicles in Illinois.

Sounds and noise

Illinois has strict regulations in place to control the amount of noise that vehicles are permitted to emit. In addition to the sound systems and muffler, Illinois also does not permit the squealing of tires unless by emergency vehicles.

Sound system

Illinois regulations require that sound systems are not audible within 25 feet of property lines in residential areas.


  • Mufflers are required and must be in good working condition and not emit sounds higher than 85 decibels when going over 35 miles per hour.

  • Mufflers can’t be altered to produce sounds louder than the original manufacturer equipment.

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

Frame and suspension

Illinois has the following regulations in place for the vehicle frame and suspension systems:

  • Vehicles can’t exceed 13 feet 6 inches in height.

  • Suspension modifications can’t lift or lower the vehicle bumper height by more than three inches.

  • Vehicles under 4,500 GVWR have a max frame height of 24 inches.

  • Vehicles from 4,501 to 7,500 GVWR have a max frame height of 26 inches.

  • Vehicles from 7,501 to 10,000 GVWR have a max frame height of 28 inches.

  • Vehicles 4,500 pounds and under have a max front bumper height of 24 inches and rear bumper height of 26 inches.

  • Vehicles between 4,501 and 7,500 pounds have a max front bumper height of 27 inches and rear bumper height of 29 inches.

  • Vehicles between 7,501 and over 9,000 pounds have a max front bumper height of 28 inches and rear bumper height of 30 inches.


Several counties in Illinois require emissions testing. Visit the DMV website in your county to find out if it is required.

Lighting and windows


  • Red and white rotating or flashing lights are not permitted on passenger vehicles.
  • Flashing amber lights are not permitted on passenger vehicles.
  • Blue stationary and flashing lights are not permitted on passenger vehicles.
  • Fog lights are allowed.
  • One spotlight is permitted.

Window tinting

  • Non-reflective tint can be applied to the top six inches of the windshield.

  • Front side windows, back side windows and rear window must allow more than 35% of light to pass through.

  • All window tint must be non-reflective.

Antique/classic car modifications

Illinois requires street rods and custom vehicles to be titled and registered by the make of the vehicle’s body and the year that it was created to resemble.

  • The vehicle is considered a street rod if it resembles a model from 1948 or older.

  • The vehicle is considered a custom vehicle is it resembles a 1949 model or newer.

  • Vehicles that are 25 years or older and have the original equipment must have an antique plate.

If you want to make sure your vehicle modifications are in compliance with the modification laws in Illinois, 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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