Car Modification: How It Will Affect Your Car Insurance

The reason why car manufacturers mass-produce a variety of car models is that they are aiming to attract the biggest audience they can to their brand. This is great for them, but it ends up meaning that every car they product looks the same, so as an owner, you’ll have to deal with knowing that your car is identical to all others of the same model. Many car owners enjoy driving a car that has been customised to their visual and performance-related preferences. However, every modification to a car can affect your insurance premium, so it’s important to do your research before you make any modifications. According to, car insurance prices have increased by 5% (£37) in the last 12 months, taking the total typical insurance policy to £789. 

In this post, we are going to give you tips on how you can modify your car in the most suitable way, adding your own personality to it, and what you must declare in order to avoid your insurance being affected. 

Has My Vehicle Been Modified?

A modified vehicle is a vehicle that has been altered in any way since it underwent the manufacturing process and has had significant changes from factory standard settings. The modification can be as little as a bumper sticker, or as big as a new engine unit being installed. A performance modification is a change that will improve your vehicle’s performance, and a cosmetic modification is something that alters the appearance of your vehicle.

Why Should You Declare Your Car Modifications?

Your responsibility as a policyholder of car insurance is to ensure that you declare any modifications, no matter how minor they may seem. The reason that it is so important that you declare any changes is that your car modifications will most likely increase the potential financial risks for your insurance provider. Some factors that your insurance company will consider when giving you an insurance quote is the make and model of your car, personal information (such as age and driving experience) and the national statistics at the time of the policy schedule. 

However your vehicle has been modified, by yourself or by someone else, you must update your car insurance as soon as possible after every modification. This is important because otherwise, you’re at high risk of your insurance being invalidated and you won’t remain covered. Therefore, if you don’t declare now, your insurance in the future will be harder to get and will be more expensive once you do get it!

This also applies to when you buy a second-hand vehicle. If you’re unsure of what modifications have been done, or whether any have been done at all, get the car checked immediately.

What Type Of Car Modifications Should Be Declared?


These modifications can increase the risk of an accident, so it’s very important that they’re declared. Some areas in the engine that can be modified are exhausts, transmission and air filters. According to Money Supermarket’s research on 2.3 million modified vehicles, modifying your transmission can increase your insurance by 63%, and exhaust and air filter changes can increase it by at least 25%.


Engine Size

One tip when modifying your engine size is to stick to an engine that is the same size as it was before modification. By decreasing the size of the engine in a smaller car, you can also improve fuel efficiency whilst also further improving your cost of insurance. 

Engine Control Unit (ECU)

The role of an ECU is to control the fuel-air mixture in the engine to increase power, and these will be installed in the manufacturing process. However, manufacturers tend to programme the ECU’s way below the extent to which the car is capable of, so a tip would be to reprogramme the ECU by replacing the chip inside to make it more economical. This modification will only affect your insurance slightly (5%).


Modifications to wheels will increase the value of the car, resulting in the need to inform your insurance company. Some examples of wheel modifications are installing wider tyres/wheels which could increase your insurance by 18%. 

Alloy Wheels

These wheels are much lighter than pure steel wheels, decreasing the resistance when steering. Research shows that alloy wheels could increase your insurance by as little as 8%. However, if you live in an area where alloy wheel theft is common, they are more likely to affect your premium by a higher amount. Therefore, it’s important to get your wheels checked by your insurance company pre-quote. 



Modifying the bodywork can put your car at a much higher risk of theft, so you must get these modifications assessed by your insurance provider. Some examples of bodywork done to your car are flared wings, body kits, spoilers, and light additions or changes. Most of these features are made from fibreglass and polyurethane, causing the body kit to splinter if the car was to crash. This means your insurance can increase by 10-15%, but if you already have an insurance policy with your provider that includes previous modifications, and the bodywork doesn’t significantly increase the value of your car, this makes it less likely that it will affect your premium.

Front and Side Skirts

These decrease the ground area around the car which is dangerous, especially if travelling on uneven roads. As such, they increase the level of risk that the car will be severely damaged, meaning that insurance companies will likely increase their rates.


Altering your brakes can significantly change how your car works on the road, increasing safety by decreasing the braking distance. So, if your car is already highly modified, you can improve your braking system which helps decrease your insurance by 10-15%


Carbon Ceramic Discs

These cause your brakes to cool down at a faster rate as the air passes through, helping to improve braking performance. However, these discs can actually increase your insurance because your car will increase in value once they are installed. 

Water Cooling Systems

One tip is to install cooling systems such as misting systems; this is because these are cheaper alternatives to the carbon-ceramic discs and they’re unlikely to increase the cost your insurance. However, by improving the performance of your brakes, there is a chance that your insurance premium will actually go down.



You can lower your car as long as it doesn’t affect the steering or headlight aim. An official guide by The Vehicle & Operator Services Agency (VOSA) was published, in order to help you make sure that your vehicle passes the headlight aim check. You can find it here

Lowering is unlikely to affect your insurance, but if you over-lower your car too much, it can affect how it performs on the road; for example when the car goes over speed bumps.


Bushings are rubber components that reduce the vibration and friction between metal, by providing a cushioned layer between each piece. Replacing rubber bushings with polyurethane ones is a good decision because they’re longer lasting and will not affect your premium as long as you declare them. They will also help to improve the lifespan of the various parts of your vehicle.

Sway Bars

These bars help to connect the left and right wheels together to avoid weight transfer on one side over time. The bar helps balance the weight transfer between the wheels and can help you save up to 5% on your insurance if your car is already highly modified.


Short Shift Kits

Short shift kits shorten the distance between each gear change and can be common with racer drivers and younger drivers. These can make your car harder to drive before you get used to the modification, but will only increase your insurance by up to 10%.

Gear Knobs

Changing your gear knob is another common modification. However, doing this could affect your ability to change gears efficiently, but they won’t necessarily affect your insurance. That said, it’s still important to inform your insurance provider about these.


There are many examples of how you can modify the interior of your car. A few common examples are removing or replacing seats, changing the pedals, adding in LED lighting or changing the steering wheel. 

Reupholstering Seats

If you have a standard insurance policy with no previous modifications, changing the seats in your car could increase your insurance policy up to 27%. This is because it will change the driving position for the vehicle, altering the handling.

Sound Systems


Certain sound systems are designed especially to maximise the bass in a car. These are usually reasonably priced, so shouldn’t affect your insurance unless you invest in a higher-priced system.


Tinted Windows

As stated on GOV.UK, the law since 1985 is that the front windscreen must let in at least 75% of light, and the front side windows should let in at least 70% of light. However, there is no law on how much light must come through the rear windscreen or rear passenger windows. Not following this law can cause the driver to receive a prohibition notice which stops them using the car until the extra tint is removed. If the legal amount of tint is added, this could increase your insurance by up to 16%.

Neon Lights

There are many different lights that may affect your insurance or could be prohibited as a whole. An example of lights that are banned would be any form of flashing lights. On top of this, lighting that is too bright for other drivers is also against the law. The only colour of lighting allowed on the front of the car is white, and red lights are only allowed on the back to avoid confusion to other drivers. Green lights are against the law to have on your car exterior. Any lighting changes can increase your insurance by up to 12%.

Paint Jobs and Stickers

These types of modifications will usually be paid out by insurance companies after you have an accident, but if the insurance provider has had numerous previous pay-outs with these, they might not be willing to do the same in future with other drivers.


Other Ways To Save On Your Insurance

If your car is highly modified and your insurance has bumped up, there are a few ways in which you can save without removing these modifications:

Improve The Security

Improving the security in your car increases its chances of not being stolen or broken into. Some examples are alarms, tracking systems, steering locks and simply hiding your valuables. There are also car immobilisers which stop someone else from starting your car if they don’t have the key, which will stop your car from being stolen. However, your car could still be broken into, so using this with another security system, such as an alarm, will be more beneficial.


Add A Named Driver

Adding another driver that drives the car occasionally could reduce your insurance costs, as long as you are the main driver of the car. However, try to avoid adding drivers that are young and inexperienced because this could actually increase your insurance costs.

Fronting – When someone that uses the car the most is an additional named driver.

If you are caught fronting, it gives the insurance provider the ability to completely cancel your insurance policy, or even charge you the correct policy amount up front! This can lead to the driver being blacklisted by all other major car insurance companies, so avoid this at all costs!

Black Box Insurance

This is a device fitted into your car that uses telematics through GPS systems so insurance providers can track your driving ability. This includes a number of factors, such as your location, how long you’ve been driving for and how harsh or smooth your braking is. This then allows you to prove to your insurance company that you are a safe driver. Therefore, this will lower your insurance costs rather than base your costs on the typical driver.

Are You Looking To Modify Your Car Wheels?

If you are looking to modify your current car wheels or need more guidance on any of the information above, then check out our online shop or contact us today on 01274 864457.