Modding Your Car – Hot Tips and UK Laws

Here’s a guide to some popular mods in the UK and some considerations to make before you commit!

Modding Your Car – Hot Tips and UK Laws

As much as you may love your factory-spec car, some motor enthusiasts will tell you there’s nothing like driving a car that’s been tailored to your own specific tastes. Whether this means changes to performance (brakes, engine, suspension) or the look of the car (spoilers, lights, body kits), car mods can turn your factory model car into something truly unique. 

However, there are a few things to consider before making your car a contender for the next ‘Fast and Furious’ movie. Certain mods may affect your insurance, and still others are completely illegal in the UK. Here’s a guide to some popular mods and some considerations to make before you commit.

Tinted Windows

Tinted windows are a fairly common mod and a way to make any car look cooler. However, there are specific laws in the UK that govern how far you can go with this particular one. There are no regulations on tinted windows on rear passenger windows or the rear windscreen, so you can do what you like there. 

However, the front windscreen of your car must let at least 75% of light through and the front side windows must let at least 70% of light through. So tinted windows are legal, within limits. The average car window tinting in the UK costs around £250-£500 and most of this cost is installation, meaning it’s considerably cheaper if you can do it yourself.

Lowered Suspension

Lowering the suspension on your car will change the performance and handling of your car, so drivers need to be careful when starting to drive their newly-modded ride. But lowered cars usually have better aerodynamics, cornering and traction, and look great too. This is a popular mod, especially among car owners who want a fast ride that they’ll be driving on well-maintained roads. 

Lowering your suspension is completely legal in the UK, however the suspension is one of the elements they’ll be looking at in the MOT test. This means you’re going to want to have any modifications performed by a competent mechanic who guarantees their work will keep you street-legal.


Spoilers are another common mod and luckily they’re usually legal in the UK. Having the right spoilers on your car can improve handling and aerodynamics, as well as giving your car a sportier look. Once again, your spoilers will come under review in your MOT check: the three things that will get you in trouble are the connection, the edges and visibility. 

In order to be legal, your spoilers need to be fastened safely to the body of your car, so once again it’s worth finding a competent mechanic who will do this properly. The other things that will get your spoiler banned are sharp or protruding edges, or if it obscures your vision while driving. But unless your spoiler is particularly outrageous or poorly installed, you should be fine.

Lights and Neon

Changing your lights may seem like a cheap and easy way to alter the appearance of your car, but this is an area that’s heavily regulated in the UK. For starters, your front headlights must be either white or yellow, and can’t be dimmed below 50%. If you want brighter lights, be wary of any halogen bulbs with a colour temperature over 4,200K. These lights have a blue-ish tint which makes them illegal in the UK (to make sure civilian cars aren’t confused with emergency vehicles). Rear lights have to be red, and only red.

Neon and particularly under-neon lights look cool, but are unfortunately almost always illegal in the UK. Any exterior lights that may distract other drivers are completely banned. This includes any bright, colourful or flashing lights either inside or outside the vehicle. Under-neon is basically illegal; you might be able to get away with it if the neon only lights up when the car is parked, and if the neon tubes themselves aren’t visible.

Bigger / Louder Exhaust

An improved exhaust system may improve the horsepower of your car, but modders are mostly looking for a noisy exhaust that creates a show. A loud, growling exhaust gives the impression of a powerful, high-performance engine. However, this is also the thing that makes most exhaust mods illegal.

All cars in the UK have a noise limit of 74 decibels and must also comply with emission regulations. Not only that, but excessive noise or exhausts are pretty easy for police to spot, meaning that cars that don’t meet requirements are likely to be pulled over soon after being modified.

Nitrous Oxide

We’ve all seen it in the movies. One of the characters is out street racing or outrunning the police. Their foot is to the floor but they still need more speed, so they flip a switch and let their NOS tanks rocket them down the road like a jet engine.

In real life, using nitrous oxide in cars is extremely dangerous. The compressed gas increases the pressure on the car’s cylinders which can cause damage and, in extreme cases, the engine could even explode. Despite this, nitrous systems are actually legal in the UK, with some caveats.

The laws concerning NOS tanks have been unclear in previous years, meaning that some police may (incorrectly) believe them to be illegal. This means that cars using nitrous could be pulled over, even though they’re technically legal. Insurance companies have concerns about nitrous-enabled cars due to possible engine damage and increased risk of accidents, so premiums are likely to be considerably higher, or your company may flat-out refuse to cover a NOS-fitted car (more on this below). 

Although private vehicles aren’t, technically, legally required to display a green ‘compressed gas’ sticker, it makes sense to do so in case of accidents. And finally, cars fitted with nitrous are still subject to the same speed and road safety laws as any other car, meaning this is a mod best suited for those drivers who plan on taking their car to a legal race track.

Important Note – Insurance

In pretty much all cases, modifications to your car may affect your insurance. Performance mods may put your car at greater or lower risk of accidents, while making your car more attractive and unique may unfortunately make it more of a target for thieves. Also, modding your car may increase it’s value which, again, may have an effect on your insurance. It’s not all bad news though; some mods may make your car safer and actually lower your insurance premiums.

The most important thing here is to inform your insurer of any mods you install on your car. If you don’t, there’s a possibility that you may be denied when you make a claim, or you may have to pay excess fees or penalties. And when we say ‘any mods’ we mean exactly that, not just big mods like a dropped suspension but even small changes like adding satnav or a better stereo. The smart thing to do is to play it safe and inform your insurer of any and all changes you make to your car.

This article was brought to you by Quick Car Finance, a leading UK car finance company with a Trustpilot review score of 4.9/5.

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