The Guide to Legal Car Modifications in New Hampshire

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Whether you live in New Hampshire or plan to move there in the near future, you need to understand the laws surrounding vehicle modification. Understanding the following regulations will ensure that your vehicle is street legal when driving on the roadways throughout the state.

Sounds and noise

New Hampshire has regulations in place that cover the muffler on your vehicle. Failure to follow them can result in a $100 fine for the first offense, $250 for the second offense, and $500 for each additional offense.

Mufflers

  • Mufflers are required on all vehicles and must be in working condition to limit unusually loud or excessive noise.

  • Muffler bypasses, cutouts, and similar devices are not permitted on roadways.

  • Straight pipes are not permitted.

  • After-market exhaust systems are permitted providing they are not excessively loud (exact loudness levels are not defined).

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

Frame and suspension

New Hampshire does not have frame or suspension lift height restrictions. However, other regulations include:

  • Vehicles cannot be more than 13 feet 6 inches in height.

  • Minimum bumper height for cars, SUVs, and trucks is 16 inches.

  • Cars and SUVs bumper height cannot exceed 20 inches.

  • Truck have a maximum bumper height of 30 inches.

  • Lowered suspension systems cannot allow any part of the chassis, steering or suspension on the vehicle to be lower than the lowest portion of the wheels.

Engine

New Hampshire does not have engine modification or swap regulations. However, annual safety inspections are required. Emissions testing is also required for vehicles manufactured after 1996.

Lighting and windows

Lights

  • Two spotlights are permitted providing that the high-intensity part of the beam does not strike windows, mirrors or the windshield of another vehicle on the roadway.

  • Three auxiliary lamps are permitted.

Window tinting

  • Non-reflective tint is permitted on the top six inches of the windshield.
  • No tint is permitted on the front side windows.
  • Back side and rear windows must allow over 35% of light through.
  • Side mirrors are required if back window is tinted.
  • Reflective tint is not permitted.

Antique/classic car modifications

New Hampshire provides Antique plates for vehicles that are more than 25 years old. However, these vehicles can only be used for public interest activities such as parades, club activities, and exhibitions.

If you want your vehicle modifications to comply with New Hampshire law, 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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Related questions

Engine modification
Sounds like a nice build. Assuming you used the 305 crank, the engine will still be called a 5.0 or 305, since that is the cubic inch displacement of the engine.
I am looking to make a "sports" , "dub" car with alot of power.
Taking on a project such as this takes lots of time, even for the most experienced mechanic. You will be re-engineering your car and this will require you to learn a lot and make a lot of decisions. There is...
i cut off the roof
If you still have the windshield and install a roll bar then you should not have a problem, but if I were you I would check with local ordnance to make sure it is legal.

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