Vehicle Mod Laws in New Hampshire

Replacing the exhaust system is legal in New Hampshire, but a muffler in good working order is required and cutouts or bypasses are prohibited. There is no statutory 'no louder than stock' rule — the standard is that the exhaust must not produce excessive or unusual noise.

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New Hampshire sets no statewide decibel limit for passenger cars. A muffler in good working order is required, exhaust may not produce excessive or unusual noise, and cutouts or bypasses are prohibited.

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Smoked or tinted film on headlights and taillights is illegal in New Hampshire. Headlights must emit white light and taillights must show red at the required visibility distance, and tint that dims or discolors them violates those requirements.

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Frames are legal if nothing is obscured, and it is separately unlawful to knowingly obscure the figures or letters.

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New Hampshire requires bumper height within a band: 16 to 20 inches on private passenger vehicles and 16 to 30 inches on all others, measured from level ground to the bottom of the bumper with tires at maximum pressure.

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New Hampshire names the product directly: since September 2024, aftermarket LED light bars, flood-style pod lights, and roof or roll-bar mounted lights may not be illuminated while operating on a way. They must be off, not covered.

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New Hampshire sets a real floor: if the suspension has been altered, the bottom edge of the horizontal bumper bar must sit at least 16 inches above level ground, and no more than 20 inches on a passenger car (30 on an MPV or light truck).

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Underglow is legal in New Hampshire, including while driving, subject to color and flashing limits: All forward-facing light must be white or amber and rear light red; there is no underglow-specific ban.

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New Hampshire requires suitable fender guards or flaps on any vehicle not equipped with proper fenders, effectively reducing throw, spray, and splash from any wheel or tire. There is no numeric protrusion limit.

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Aftermarket windshield tint is prohibited except a strip no wider than 6 inches at the very top, and that strip must still pass at least 35% light — which an opaque banner cannot. Because the material must be transparent, a printed or opaque banner is not legal in New Hampshire — only a clear tint band.

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Front side windows: minimum 70% VLT. MPV and pickup windows behind the driver follow the federal standard.

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