What Are the Legal Car Modifications in Arizona?

Owning a car is the first step towards becoming a gearhead. Not everyone sees their vehicle as a simple tool to get from point A to point B, so they want to push it to the limit by modifying it in both performance and aesthetics. However, it is really useful to brush up on your knowledge of what is and isn’t legal.

There is no across-the-board set of rules on what you can and can’t do with your car so it can be tricky to find information on what level of customization you are permitted to do to keep your car street legal. If you live in Arizona however, this information will be useful to you as this will teach you what is and isn’t legal for car modifications. 

Window Tinting

Window tinting is one that is actually pretty close to a universally recognized car modification. The reason is that cops need to be able to see into vehicles for safety purposes, so there is a limit in many places on how dark a tint can be. The tints from SmartFilmAZ.com show how dark it can go, which is 33% transparency of light as the lowest for the front driver and passenger side windows. It still allows the privacy of things inside your car from people looking in but isn’t too dark. Similarly, red tints aren’t allowed, but reflective/metallic is on the back driver and passenger side windows, as well as any darkness for those back windows.


Mufflers are a car modification that can be done to improve performance, but sometimes people like to modify them to increase sound. In Arizona, the wording is vague on how loud is excessive, but the idea is that your muffler and exhaust system shouldn’t be making too much noise to disturb the peace. Muffler bypasses aren’t allowed either for highway legal cars and there can’t be excessive smoke coming out, which is something that diesel trucks often get hit with.

Sound System

Between the hours of 11 PM and 7 AM are considered “quiet” hours by city ordinance, which is common for most municipalities or townships. This means a sound system and the radio can’t be played at excessive volumes that disturbs the peace. This is again rather vague as there is no set decibel range, but it’s safe to assume that subwoofers or amplifiers of most types are permitted assuming they aren’t used improperly.

Car Lights

Firstly, to answer a burning question from many people in the car modification community, car underlighting is considered legal (amber or white only, however) in Arizona. Secondly, the actual lights of your vehicle do have to be within a certain power and range. 300 candlepower is the maximum level for front headlights with a range of 75 feet, to prevent the blinding or impairing the vision of other motorists. Like in most jurisdictions as well, flashing lights or red and blue lights are illegal as well.


Emission testing is something that must be passed for all vehicles in the state of Arizona when it comes to your engine. However, there doesn’t seem to be many laws regarding modifications to the engine itself, with the exception of cold air intake because of engine emissions testing. Most engine modifications still belong under the assumption of driver integrity for following the speed limit and such.

Suspension and Lift

The suspension of your vehicle is not limited to a specific low, but the lift of the vehicle is capped at a total height of 13 feet and 6 inches. This is a truck law that is set in place for tractor-trailers for height clearance under bridges and other overhangs, so your vehicle can be lifted given it’s under this limit. Fenders and mud flaps are required for lifts too.

Classic Cars

For owners of antique and classic cars, you might think you’re off the hook because your vehicle is older, but there are still some restrictions in place. They primarily involve the inspection and recertification of their safety for current standards, as well as some safety improvements to the body. Other parts include drivetrain, suspension, and brakes to make them suitable for road use based on current standards as well. They’re modifiable, but should be certified to retain their road-legal status.

Modifying a car is a good way to make your vehicle your own, but it also comes with a price. Not just the value of the parts of labor, but the cost of making sure you do the research to ensure your car is safe and following the rules. These modifications are some of the ways to maintain your vehicle’s legal status in the state of Arizona.


Will Hopstetter
Will is an automotive market enthusiast living in the United Kingdom. He holds a diverse background in automotive and enjoys utilizing that to produce insights into the inner workings of the industry.