10 Popular Car Modifications

As long as you stay within your state's limits for ride height adjustments, an aftermarket suspension system is totally legal. Furthermore, the right aftermarket suspension system can be a great way to upgrade your car's performance. When done right, your car will handle much better, and you (or a qualified shop) can even tune the suspension to optimize the car for the way you drive. Whether you race your car or you just want your commute to be a little more enjoyable, a good suspension system is arguably worth the investment.

Adding a turbocharger or supercharger to your car is another popular performance modification. These devices "boost" your engine by forcing in more air, thus creating more power. Unlike nitrous oxide (see No. 1 in illegal mods), however, turbochargers and superchargers are legal as long as they don't cause your car to fail your state's emissions check or safety inspection. Let's look at California, which is the strictest state when it comes to vehicle pollution standards. Even in California, as long as you don't alter your emissions system, your upgrades are certified for use in your car's engine, and you pass the state smog check, you're good to go.

Seat upgrades are popular car modifications, whether you're a novice racer or you just want to look like one. A set of sport seats looks cool, and if you choose the right ones, they can be much more comfortable and supportive than your car's stock seat. Sport seats can even help improve your driving position. Many manufacturers of actual racing seats caution buyers that they are not suitable for street cars, mainly because racecar seats are designed to be used with race harnesses, which are not legal for use as an alternative to a car's factory seatbelt. However, some manufacturers, like Recaro, make sport seats that are legal for street use. Just make sure you can use your factory seatbelt and that installation won't disable any of your car's airbags.

An obnoxious paint job might be a crime against good taste, but it's not an actual crime. Generally, you can paint your car however you want, or get a similar effect with a vinyl wrap, as long as it doesn't look like you are trying to impersonate police or an emergency vehicle. There are a few things to bear in mind with the process of repainting your car, however. It's expensive to have a car repainted by a professional, and it's a time-consuming pain to do yourself. If you do decide to paint your car at home, check your local pollution ordinances to make sure you won't get cited for the paint and chemical fumes.

Some states have very strict laws regarding window tint. In Illinois, for example, a driver must have a documented medical condition to get away with any front or side window tint. Many other states have laws on the books restricting tint that is reflective or that makes it impossible to see inside the car. However, if you really want tinted windows, you can get away with at least some tint in most states. Tint is measured based on the percentage of light that can still pass through the windows, and states that don't ban tint outright will usually specify a range of permissible percentages.

Now for those illegal modifications.

If you've ever watched a movie about street racing, you've probably heard at least one of the characters refer to nitrous oxide, or NOS. Nitrous oxide tends to wax and wane in popularity, but there's no disputing that it's a cheap way to add a lot of power to a car. Nitrous oxide works by temporarily increasing the oxygen in the engine, which enables it to burn more fuel and thus, extract more power. It is legal to drive a car that has a nitrous system installed, but in many states, the system has to be disabled for the car to be legal for street use. That is, the bottle that contains the nitrous oxide cannot be connected to the system. Some jurisdictions suggest that using nitrous encourages unsafe driving. In short, it's legal to buy and install a nitrous oxide kit, but if you get pulled over, you'd better be able to prove you weren't actually using it.

It seems like it's been a while since underbody glow kits had their 15 minutes of fame, but trends always come around again. If neon lighting comes back in vogue, keep in mind that it is illegal in a lot of areas. In some states, you could be accused of attempting to impersonate a police officer if you add blue or red lighting to the exterior of your car, but other colors are fine. Some states just ban neon lighting entirely, since it can be a distraction to other drivers. If your state has a blanket ban on altering your vehicle's exterior lighting, this would also apply to other forms of supplemental lighting, like rally lights or aftermarket fog lights.

You might assume that racing harnesses go hand in hand with seating upgrades, but that's not true, at least if you want to keep your car street legal. Most manufacturers of race harnesses caution buyers that using a harness in place of a factory seatbelt is not legal and can put you at risk in a crash. Even though a race harness is designed to hold you firmly in place in a collision, an unfamiliar harness could delay an emergency response team's ability to get you out of your vehicle. If you do take your vehicle to the track from time to time, you still have options. Schroth is a brand that makes harnesses that can be installed without interfering with your factory seatbelts, so you can keep your car both safe and street legal.

Once you start modifying your car with performance gains in mind, it can be tempting to start messing around with your emissions controls. Emissions modifications are also popular with the diesel truck community, since some of those drivers like to annoy passersby and other motorists by blowing huge plumes of smoke, a practice known as coal rolling. However, tampering with emissions controls in any way is illegal across the country, since it violates the Clean Air Act. If you upgrade your exhaust system, make sure your catalytic converter stays in place.

Ever wonder why someone would jack up a truck so high that they practically need a ladder to climb in, or drop an old sedan so low that its belly scrapes the ground? Extreme adjustments to a vehicle's height — whether up or down — are prohibited in most states, though each state has its own guidelines. For example, some states' laws depend on the type of vehicle. That is, you can raise a truck or SUV higher than a sedan. Other states measure the distance between the bumper and the ground. The most straightforward way, perhaps, is to say that a vehicle cannot be a certain number of inches higher or lower than the car's factory ride height — though they'll have to know what that stock height is.