Which car modifications are illegal?

Neon light modifications are illegal in most scenarios.

One of the few ways you can legally spruce up your car with neon lights is if you add them to the bottom of your car – but only if the neon tubing isn’t visible, and the light isn’t too bright or flashy that it distracts other drivers around you.

In the UK, white and yellow lights are allowed at the front, while red lights are allowed for the back of the car.

Using red, green or purple tints for your headlights, or any bright neon or flashy lights on the exterior or interior of the car, are sure to get you pulled over.

Any halogen bulbs with a colour temperature over 4,200 K are not road legal as they produce a slight blue tint light. Blue flashing lights are used by emergency services such as police vehicles, ambulances, firefighters, and the coastguard. To make these services stand-out, these lights are legal only for emergency service vehicles.

Also, the lights shouldn’t be dimmed by more than 50% to maintain visibility.

If the light bulbs bear an ECE R37 regulation, it’s a sign that the lights are road legal.

You can tint your windows, but only to a certain degree.

The front windscreen needs to be at least 75% tint-free and the side windows need to be minimum 70% tint-free to ensure a clear view of the surroundings.

The only exception is if your vehicle was first put on the road before 1 April 1985. In this case, both the front and side windows need to be 75% tint-free.

It’s illegal to sell a car that doesn’t follow these rules.

A loud, roaring car sure sounds thrilling, but the noise might irritate others. An exhaust cannot cross the noise limit of 74 decibels, so any modifications that breach this limit are illegal. All cars are ‘type approved’ under the Individual Vehicle Approval (IVA) scheme before they’re sold to you, which means that they comply with the emissions and safety regulations.

Other exhaust modifications, like changes to the exhaust management system, tampering with the emissions control system, or removing some parts could make the vehicles more damaging to the environment.

Spoilers help with aerodynamic efficiency, and a slight tweak to their look can help improve handling and make the car look sportier.

While modifying a spoiler isn’t illegal, the method of modification can be.

If the new spoiler isn’t fastened safely to the car or has exposed sharp edges, you can get into trouble with the police and may even be forced to remove the modified spoiler.

Spoiler modifications should help reduce your car’s drag and weight. A rear spoiler can improve the downforce, while front spoilers can reduce drag. The modification should also be a practical size so it doesn’t obstruct your view – three inches wide and six inches above the roofline spoilers are usually considered an efficient size.

The use of Nitrous Oxide is illegal and extremely dangerous.

Adding Nitrous Oxide gas to your engine can increase cylinder pressure. If the engine’s components are unable to handle the increased stress, the engine can suffer damage.

The engine can also be damaged when there’s too much oxygen and not enough fuel in the engine (an incorrect ratio of air and fuel).

In the worst-case scenario, the incorrect ratio and added cylinder pressure could cause the engine to explode.