When And Where Is It Illegal To Modify Your Car? (2025)

Stock vs. Modified Vehicles: What the Law Says

Vehicles are often described as being “stock” or “modified.” This refers to how much the vehicle has been modified from its original state.

A stock vehicle is the same as it was when it came out of the factory. It meets all of the necessary emission and safety standards, and it’s usually under warranty. If these vehicles are in car accidents, they will be easily covered by your insurance. If something goes wrong with a basic auto part, you can file product liability claims against the manufacturer because you haven’t altered the car.

A modified car has undergone upgrades or modifications. These can make the vehicle no longer meet safety regulations and could be illegal under state or federal laws. Typically, any manufacturer's warranty will be voided if the car has been significantly altered.

Federal vs. State Modification Laws

Vehicle modifications are regulated at both the federal and state levels. The National Highway Traffic Safety Administration (NHTSA) is responsible for publishing the Federal Motor Vehicle Safety Standards (FMVSS).

These standards cover just about every safety-related vehicle feature, including:

• Brake systems
• Lights
• Seat belts
• Fuel systems
• Tires
• Electronic stability control
• Transmissions
• Dashboard displays

Vehicle manufacturers must ensure their cars meet these standards to be sold. When it comes to regulating aftermarket modifications, state laws can play a much larger role.

Generally, state vehicle codes will prohibit modifications that would make a car violate the FMVSS. However, some states impose more restrictions.

Common Illegal Mods on Cars Across the United States

Although each state has different laws on modifications, some car mods are illegal almost everywhere. These are a few examples:

Loud Exhaust

Most states have laws that require vehicles to have mufflers to reduce exhaust noise. . Some bans set a clear decibel threshold, but others are worded less precisely.

The “Carolina Squat”

This is a suspension modification where a vehicle, typically a pickup truck, has its front bumper higher than the rear bumper. Because the Carolina squat reduces visibility immediately in front of the vehicle, it could lead to car accidents.

Rolling Coal

Most states ban tampering with car emissions systems. Rolling coal is an example of this kind of tampering, which involves modifying a diesel exhaust so that it blows out black smoke. Rolling coal is not only illegal, it also reduces fuel efficiency.

Too-Dark Window Tint

A very dark window tint can make it harder to see when driving at night. If the tint is reflective, it may also produce glare that impairs visibility for other drivers.

Illegal Lighting and Headlight Modifications

Having overly bright lights is illegal throughout the United States. They don’t pose a danger to you as the driver, but they can cause car accidents because they blind others on the road. Lightbars are most likely to cause this problem, and you’ll likely be stopped by the police if they see that your car has them.

Your headlights must also adhere to federal regulations. They must have between 500 and 3,000 lumens.

What Police Look for in Illegal Car Modifications

There are some things that police officers are on the lookout for when it comes to modifications. One of these is noise. If your car exhaust noise level is above the accepted standard, which varies from state to state, then that’s a valid reason to stop you.

Other common violations they will look for include types of:

• Window tinting
• Engine modifications
• Suspension and frame modifications

Aftermarket lighting is something else that can get you stopped. This means that the lighting system has been made by a company other than the original manufacturer of the vehicle.

State-Specific Modification Regulations

Is it illegal to modify your car in your area? Each state sets its own rules, and they’re outlined in the state vehicle code. Because these regulations are so complex, you will need to review your particular state’s code for specific rules. However, it can help to have an idea of which states more strictly regulate car mods.

Some of the states with the strictest modification laws include:

• California
• Illinois
• Massachusetts
• New Jersey
• New York
• Oregon
• Pennsylvania
• Texas

Other states may be more lenient.

States with less restrictive laws include:

• Arizona
• Idaho
• Mississippi
• Missouri
• South Dakota
• Wyoming

Even if you live in a relatively lenient state for car modifications, always check to make sure a mod is legal before installing it.

Consequences of Illegal Modifications

If you’re caught with an illegal modification, you can receive a fine and a ticket. But if your car has an especially dangerous modification, you could even be charged with a crime.

You can receive a mechanical violation traffic ticket. This is one of the types of traffic tickets that is given to drivers when there’s something wrong with the vehicle. These are non-moving violations.

In some instances, it could be a “fix-it ticket.” These give you a certain amount of time to fix the problem. If you can do so, then the ticket is erased. Each state may have its own timeline to void the citation.

Additionally, if an illegal mod causes an accident, the other driver may hire a personal injury lawyer to file a lawsuit against you, and you may be liable for damages.

Legal Modifications You Can Still Make

So is it illegal to modify your car completely in certain states? Even in fairly restrictive states, there are still some modifications that are generally safe to make. These are some of them:

• Spoilers
• Wraps or decals
• Wheel upgrades
• Window tint that isn’t too dark
• Audio system upgrades

In many states, you can also install modified exhaust systems as long as they meet noise and emissions standards.

Steps to Ensure Compliance With Modification Laws

You don’t want to waste money on a car mod only to find that it’s illegal. Follow these tips for staying compliant:

• Always research your state’s laws beforehand
• Consult with an experienced mechanic
• Use only high-quality aftermarket parts
• For complex modifications, hire a professional

It’s also wise to regularly monitor your state’s vehicle code to make sure your car stays compliant with any changes.

How to Address Tickets or Legal Disputes Over Modified Vehicles

Many tickets for illegal mods - especially those considered equipment violations - are “fix-it tickets” that require you to provide proof that you've removed the modification. If you know the mod is illegal, the best course of action is usually to follow through and remove it.

However, if you want to contest the ticket, you should hire a traffic attorney. Your lawyer can come up with a defense and potentially help you avoid legal consequences.

Impact of Modifications on Vehicle Insurance

If your insurance is already fairly expensive, you might be worried about how modifications may impact your coverage. Very minor modifications like tinting your windows slightly darker probably won’t change anything.

However, because many modifications increase the value of a vehicle, your average car insurance cost per month may increase if you report them to your insurer. You also have the option of not reporting car mods.

If you do this, keep in mind that insurance policies usually only cover your vehicle’s stock parts. For instance, suppose that you buy a car and replace the stock headlights with expensive LED lights. If you don’t report the change to insurance and you’re in a crash, your insurance may not cover your upgraded headlights.

Have You Received a Ticket for Illegal Modifications?

Getting a ticket for an illegal modification can be stressful. If you’re concerned about a ticket impacting your driving record, your finances or both, it may be wise to consult an attorney.

However, in situations like these, you shouldn’t just hire the very first lawyer you come across. Your choice of lawyer can make all the difference in the outcome of your situation.

ConsumerShield can help you choose the right lawyer in your area for your needs. Fill out our simple contact form to start a free consultation today.