Are Coilovers Legal in the US?

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Coilovers are legal in the US, but how low you can go is limited by state law. States set minimum frame or bumper heights and can regulate how far a car may be lowered, so a drop that is fine in one state can be illegal in another.

Why?

Adjustable coilovers are a normal suspension upgrade and legal to fit. What varies is ride height: many states set a minimum bumper or frame height, and some specifically limit how low a vehicle can be, to keep bumpers aligned and headlights at a legal level.

Those figures differ from state to state, so a slammed setup that passes in a permissive state can be over the line elsewhere. The car also has to keep its headlights at a legal height and aim, and the tires must remain covered by the fenders.

So coilovers themselves are fine; the legal question is the height you run them at. Stay within your state's minimum-height rules and keep the lights and fender coverage legal.

What decides if it's legal

Minimum frame and bumper heights are set by each state.
The car must not sit below the state’s legal ride height.
Headlights must stay within legal height and aim.
Tires must stay covered by the fenders.

Does it depend on your state?

Yes. The minimum ride-height rules are state law, so the same coilover drop can be legal in one state and too low in another. Headlight height and fender coverage apply everywhere.

Related legality guides

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Sources

This page is general guidance, not legal advice, on the rules in the US for coilovers. The detail varies by exact vehicle and changes over time - confirm with your insurer and the EPA, NHTSA and your state DMV before modifying.