Before you trick out your car to make it go faster or look better, make sure the upgrades won’t cost you money due to fines or put your vehicle out of commission. We looked at some of the top modifications that are illegal in most states, plus a few questionable choices that probably should be illegal.
Since what is illegal varies by state, you’ll want to contact your Department of Motor Vehicles or local law enforcement before you break out the blowtorch. This does offer a breakdown of popular modifications and some guidelines, so you can find out here which car modifications are illegal — or should be.
Illegal: Loud Exhaust
If you want people to hear your car before they see it, make sure it’s not illegal in your state to have a loud exhaust. In 2019, California changed its exhaust law so that a loud muffler is no longer a fix-it ticket but rather a fine on the spot. Vehicles must have a muffler that prevents “excessive noise from the exhaust system.”
If you’re driving a passenger vehicle — other than a motorcycle — or a truck weighing less than 6,000 pounds, the exhaust can’t be louder than 95 decibels, according to the California Bureau of Automotive Repair.
Illegal: Tire Chains and Studded Tires
In most cases, tire chains are allowed in “hazardous” weather and as needed, as long as the highway surface remains undamaged. But Connecticut gets specific: Chains are legally allowed between Nov. 15 and April 30 for hazardous weather or related incidents, according to the AAA.
As for studded tires, Alaska, for example, requires the studs to be rubber and they can only be used in certain locations and during certain dates. They can be used Sept. 16 to April 30 north of 60 degrees N and from Oct. 1 to April 14, south of 60 degrees N. Meanwhile, Hawaii, Mississippi and Puerto Rico don’t permit studded tires at all.
Illegal: Radar Detector
Some states allow radar detectors for passenger vehicles but not for commercial vehicles. Others, like the District of Columbia and Virginia, put the kibosh on them entirely.
What’s considered a commercial vehicle? Pennsylvania is like many others, defining it as one that transports goods and passengers for compensation — but it’s best to consult the fine print of the law.
Illegal: Window Tint
Want to tint your windows for privacy, to filter the sun or just look cool? That’s fine, as long as you follow the law. Some tinting is allowed, but it varies wildly from state to state — and from window to window.
For example, Florida has a lengthy set of rules. Side windows can be tinted, but the material must have “a total solar reflectance of visible light of not more than 25% and a light transmittance of at least 28% in the visible light range.” Many states’ laws also allow for a “sunscreening device” that’s nonreflective, according to AAA.
Illegal: Nitrous Oxide System
This power-adder is fine on the racetrack or off-road. But you’d be hard-pressed to find a state that allows its use on the highway. And some states are particular about how you use the materials. In Maryland, you can’t possess a NOS bottle in a vehicle that’s operating on the highway.
Want to give your car’s suspension a lift? First, find out what’s OK in your state.
For example, in California, the maximum frame height is 23 inches. And Delaware doesn’t want the bumper height to exceed 22 inches from the ground to the bottom of the bumper.
Often the allowable bumper-height change is tied into the gross vehicle weight rating. For example, Maryland caps it at 28 inches for trucks and multipurpose vehicles at 10,000 pounds or less.
Mississippi law says you can’t lift the original vehicle bumper height more than 8 inches total. The front and rear suspension lift must be 6 inches or less.
Illegal: Lowered Suspension
As with lifting your vehicle, your state laws will vary for lowering it. Virginia says that vehicle suspension can’t be modified if it causes the chassis or body to touch the ground, expose the gas tank or “cause the wheels to come in contact with the body under normal operation.”
You already know it’s illegal to text while driving in almost all states (as of this writing, Missouri and Montana still allow it over the age of 21). But what about watching a video screen?
In most states, a viewer or screen is not allowed to be where the driver can see it, nor can it block the driver’s view of the road, according to AAA. GPS is usually the exception. But states like Arkansas and Georgia have no restrictions.
Illegal: License Plate Frame
Sure, you want everyone to know “Life is Good, Spread Good Vibes,” so you take to your license plate frame to share it. But that accessory might be illegal in your state.
In Washington, if a holder, frame or similar item changes your license plate or makes it unreadable — it’s illegal. You can use the item if it doesn’t cover the license and allows the license plates to be clearly visible at all times. While on the subject of license plates, your state may also consider it illegal to permanently remove the front one or to add a covering/protector over the rear one (to thwart speed cameras).
Illegal: Loud Music
You’ve added bass and a pretty tight audio system. And now, almost everyone in your neighborhood hates you. Technically, what you did isn’t illegal, but it is if it qualifies as “excessive noise,” a “noise disturbance” or “unnecessary noise.”
Generally, its legality is measured by decibels and distance. In Tennessee, passenger cars measured at 50 feet have a maximum allowable 78 decibels; at 25 feet away, it’s 84. Keep this in mind if you’re planning to add an alarm to your car.
Illegal: Roof Rack
In general, you can add a roof rack to your vehicle. You can add your stuff to the roof rack. Just don’t be top-heavy.
In most states, there are preferred safe, legal ways to transport your cargo. That includes a maximum height, length and width law. In Oregon, the vehicle height, including load, cannot exceed 14 feet.
Not to mention, you need to secure your goods. There is a slew of violations that would come with anything dropping onto the road.
Illegal: Air Freshener
Hanging an air freshener or even fuzzy dice from your rearview mirror could be a violation in your state. For example, California prohibits placing an object that “obstructs or reduces the driver’s clear view through the windshield or side windows.”
In Virginia, it’s considered illegal to drive on the highway if there’s anything hanging anywhere in the car that could block the driver’s clear view of the road through the windshield and the front side windows.
Illegal: Making Your Car a Party Limo
Want to modify your vehicle into a limo? It might be tough if you’re in Ohio, where the law prohibits any part of the car body from being attached to the frame beyond the original design. By doing some kind of custom limoing, you’re altering the structural integrity of the original frame as well as the capabilities of the stock brakes to due to the added weight.
You might also have to remove some airbags, so safety’s further reduced. There’s also the fact that you’d be driving illegally if you don’t have a special driver’s license like a chauffeur license and/or commercial driver’s license.
Illegal: Auxiliary Lights
More lights make for better visibility — for you. But for oncoming traffic, it might feel like driving directly into the sun as your vehicle approaches. There are laws about what level of candlepower and how many lights you can add.
For example, in Alabama, you’re limited to two side cowl or fender lamps and one running-board courtesy lamp per side. The state also requires those lights to shine in amber or white with no glare.
Illegal: Neon and Under-Body Lights
Under-body lights can be a scene-stealer. But it might be a traffic violation in your state to have under-body lights — neon or otherwise — while driving on a public road. Such as it is in Maine, where you’re permitted to have under-body lights for events or competitions, but not while you’re driving on the road.
Illegal: Bigger Tires
If your new bigger, beefy tires and wheels stick out from the wheel wells, you may be breaking the law. Utah requires the top half of the tires to be “covered by the original fenders, by rubber, or other flexible fender extenders under any loading condition.”
In Rhode Island, drivers aren’t permitted to travel on the highways if the tires extend beyond the fenders or body of the vehicle — unless it has flaps or guards “to reduce spray or splash to the rear and sides.”
Illegal: Engine Modifications
The California Air Resources Board (CARB) studies aftermarket parts closely before approving what will ultimately be installed on an on-highway vehicle. It’s a big deal, as they’re trying to avoid products that will add emissions to the air or reduce fuel economy, whether it’s an exhaust system, cold-air intake and so on.
A vehicle could also fail the smog check as a result of a non-CARB-approved engine component. So make sure what you install is legal in your state and not homegrown in your garage.
Illegal: Exhaust Emissions
When it comes to exhaust emissions, we like how Rhode Island doesn’t mince words. All motor vehicles should have a muffler in good working condition and always operating “to prevent excessive or unusual noise and annoying smoke.”
Texas feels the same about a tailpipe’s “annoying smoke”—“state law prohibits any person from operating a motor vehicle emitting visible smoke for 10 seconds or longer on Texas roadways.”
Have a diesel? Don’t bother with engine modifications that can cause “rolling coal.” This happens by tricking the engine into thinking it needs more fuel so it blows out a load of black smoke from the exhaust pipes.
As for show-offs, Colorado prohibits “engaging in a nuisance exhibition of motor vehicle exhaust.”
Illegal: Colored Headlights
Don’t be tempted to screw in colored bulbs. States frown upon this, and you’ll frown upon the fine.
In Montana, you can’t drive a vehicle on a highway if it has headlamps that are made with, covered by “or treated with a tinted or colored material, substance, system, or component that obscures the headlamps or diminishes the distance of visibility required by this section.”
Should Be Illegal: Over-the-Top Vehicle Wraps
Sure, painting and airbrushing murals on a vehicle still happens, but often what’s more appealing is the application of a vinyl wrap, which can be removed much easier, especially when you break up with the person to whom the ode exists.
You can use the custom-wrap configurator at Custom-Car-Wraps.com to do see what your vehicle would look like with a wrap, but keep in mind that other drivers might be staring at your car for the wrong reasons. And, most importantly, don’t take it too far.
Remember the wrap that caused an uproar back in 2013, you know, the one that gives the illusion that someone is bound and gagged in the bed of the truck? By comparison, it makes the wrap in which the driver appears to be sitting on the toilet almost enjoyable.
Should Be Illegal: Twinning With Your Car
You’ve probably seen photos of people who look like their pets. But people who resemble their vehicle also exist.
Take Angelyne, who famously appeared on billboards in Los Angeles over the past few decades and to this day drives a hot pink Corvette in Hollywood. She wears hot pink to match and seems somewhat customized to complement the ‘Vette, too.
That’s how a local Hollywood legend got started. But that doesn’t make it right for others to follow suit.
Should Be Illegal: Hitch Nuts
Haven’t heard of “truck nuts”? If you’re having trouble imagining, we’ll be blunt: They’re fake testicles hanging from the back of a vehicle, like from the hitch.
They had their heyday in the 1990s, but you’ll still spot them around town, even though lawmakers in a few states tried to ban them. Some locales even issued fines for them, deeming them obscene. Nowadays, there should be a fine simply for engaging in a trend from the 1990s.
Should Be Illegal: Gold and Diamond Cars
We don’t have a problem with a car in gold paint, per se, but a gold-plated or diamond-encrusted car? As if the car weren’t expensive enough — McLaren, Mercedes-Benz and Ferrari have at times served as canvases.
But you have to be one of the richest people in the world to install gold and jewels on your cars. To create this kind of buzz and drop jaws can cost upward of $5 million. Please, police: Light it up, then write it up.
Should Be Illegal: Tires or Wheels That Cost More Than Your House
Wheels and tires can be affordable. They can also be expensive. And then there’s the astronomically expensive set of four car tires by Dubai-based company Z Tyres for $600,000.
When did the price of rubber get so high? Maybe it’s because they’re adorned with 24-karat gold and diamonds. They were designed in Dubai and built in Italy, then went back to Dubai for gold leafing. At least for $600,000, it was a complete set. (On the upside, all the money went to charity.)
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