Customizing your car can be thrilling, but not all modifications are legal. Some tempting modifications could result in expensive fines and legal troubles. Before making any significant upgrades, understand which mods might seem harmless but are illegal. Avoid these 15 banned customizations to keep your car street legal and avoid trouble with the police.

Underbody Neon Lights

Those colorful underbody neon lights may look fantastic at night, but many states prohibit non-standard auxiliary lighting that could dazzle or distract other drivers. Avoid this mod unless you want flashing lights in your rearview mirror.

Stretching Your Tires

Stretching tires beyond their recommended fitment can give your ride an aggressive stance. However, this decreases tread depth and impacts handling, making it illegal and unsafe in most states.

Excessive Window Tinting

While some window tinting is permitted for UV protection, going too dark on your windows can limit visibility and earn you a ticket. Most states regulate how much light must pass through.

Removing Catalytic Converters

While removing the catalytic converter may help you save some cash upfront, it’s illegal almost everywhere due to increased emissions. Your local smog check will catch this unlawful mod.

Non-DOT Approved Lighting

From high-intensity Xenon bulbs to underglow LEDs, any non-approved lighting can fail inspection and bring you fines. Stick to Department of Transportation-certified lights for street use.

Straight Pipe Exhausts

That loud, unmuffled exhaust may sound awesome but will likely have you singing a different tune when police cite you for excessive noise violations caused by removing emissions equipment.

Lowering Beyond State Limits

An aggressively lowered or “slammed” stance can certainly capture attention but may be unlawful if the frame or body components strike the ground. Most areas enforce minimum ground clearance limits you need to clear.

Removing Federally-Mandated Equipment

Ripping out your car’s catalytic converter, muffler, or even side mirrors may seem like an easy mod, but removing federally mandated safety equipment will fail you at inspection time.

Improper Lifting & Oversized Tires

Lifting modest trucks and using bigger tires is legal. However, extreme lifting cases with tires spilling beyond the fenders will cause law enforcement to cry foul for excessive raises and unsafe tire clearance issues.

Non-Certified Engine Swaps

Dropping a larger, non-stock engine into your ride can be a nightmare for emissions testing. Unless the new powerplant is certified for that chassis, be prepared for potential registration headaches.

Mismatched Lighting Colors

Having mixed bulb colors from different lighting temperatures can seem like an easy face-lift but is often illegal due to the uneven, distracting glare non-matched lights can cause.

Unauthorized Trailer Hitch Modifications

Modifying trailer hitches beyond manufacturer specifications or without proper engineering certification can compromise towing capacity and pose a hazard to other motorists.

Tinted Headlight Covers

While tinted or smoked headlight covers give a custom look, they also reduce essential nighttime visibility, which makes them unlawful in most jurisdictions that want to keep roads bright and safe.

Obscured License Plates

Customizing or tinting over your license plate to make it unreadable might seem innocuous, but deliberately obscuring it runs afoul of the law in every state requiring visible plates.

Race-Only Stancing Modifications

Maxed-out camber, stretched tires, and extreme lowering may turn heads at the track, but crossing over to street use makes these race-bred mods blatantly illegal for public roadways.