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Friday, Dec. 26, 2025

Are noisy aftermarket mufflers illegal in Colorado?

Cassis Tingley, The Colorado Sun
yes

State law prohibits any changes to vehicle exhaust systems that increase the noise mufflers make. 

Coloradans can replace their mufflers with alternative models only if they make the car no louder than the original muffler. All motor vehicles are required to have an “adequate” muffler ​​to “prevent any excessive or unusual noise,” and modifications that cut off or bypass mufflers are banned by state law. 

Most people ticketed for the Class B traffic infraction face a maximum fine of $100, but drivers of commercial vehicles can be fined up to $1,000 starting July 1, 2027.

Some cities and counties have noise prohibitions that may apply to mufflers. Denver limits daytime noise in public places, including from vehicles, to 75 decibels. Colorado Springs limits noise from motor vehicles under 10,000 pounds to 85 decibels. 

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