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Motorvation Bedford’s guide to car modifications

Some drivers want a car that really stands out from the crowd. A loud exhaust, shiny new wheels, a sleek body kit and a big spoiler are all ways to change the way your car looks and sounds. Modifications can also be made under the bonnet to improve the performance of the car. However, there are potential legal issues with making modifications to a car, not to mention the need to inform insurers of any changes.

Implications of Modifications to Insurance

The insurer of the car must be informed of any changes to the car. If the car is involved in an accident and modifications are subsequently discovered the insurance can be deemed invalid. So, they can refuse to pay out and the driver will be left to foot the bill and the police will become involved as the driver has been driving without valid insurance.

Modifications are likely to increase the insurance premiums as they can affect the car’s handling and make it more desirable to thieves. Though it may be tempting not to tell the insurer to avoid paying extra, the result is the same as not having insurance at all, so let them know as soon as the modification is carried out. Ensure you stay safe, legal and insured.

In Car Entertainment (ICE)

In car entertainment

The aftermarket in-car entertainment business is booming, just like the speakers they provide! Thousands can be spent on in-car entertainment, a new stereo, sat nav, amp, screens, games console, speakers, sub-woofers and just about anything else you can think of can be put into a car. Just remember, cars aren’t great at keeping sound in. If the car is in a public place and the music is turned up on a large stereo system, it will annoy residents and the public.

Police have the power to seize any vehicle that is causing an annoyance to the public. Though seizing of cars is usually reserved to persistent offenders, it is not unheard of for cars to be seized without warning.

If DVD players, games consoles or screens are fitted, they should not be able to be seen or used by the driver while the car is in motion, for obvious reasons. Distractions can cause serious accidents and if they are found to be in use while a vehicle is being operated it can lead to hefty fines, points, court appearances and driving bans. There are many offences that it could lead to including careless driving, dangerous driving or driving without due care. More importantly, the risk of an accident is greatly increased. If a DVD, TV or similar device is installed, never use it unless parked up safely.


aftermarket spoiler

Spoilers are used in motorsport to improve the handling of a car by providing down-force, pushing the car down. However, a road car is much more likely to have an aftermarket spoiler fitted for aesthetic reasons. The car may look ‘sportier’ but wouldn’t really gain any performance enhancement from it, certainly not at the legal speed limits of most UK roads.

When fitted, a spoiler should be securely attached to the car and not have any sharp edges that could cause damage to other cars, pedestrians or cyclists

Tinted windows

tinted windows

Tinted windows are one of the easiest modifications to make to a car. DIY tinting kits can be purchased relatively cheaply and installed with basic instructions. There are laws to they level of tint that can be applied to the windows of a car. The front windscreen must let at least 75% of light through, while the front side windows must let in a minimum of 70% of light. This is to ensure that the driver can see properly in darker conditions. Rear windows and rear windscreens have no restrictions.

If stopped by the police, a driver with window tints that do not comply with the laws may be issued a prohibition notice or issued with penalty notice or court summons. A prohibition notice prevents the car from being driven until the offending tint is removed. The tint film can be removed easily with a little effort and can be done at the roadside. Many police cars carry a device that can measure the amount of light that a tint is allowing through.

Wheels and Tyres

white wheels with low profile tyres

A big set of wheels can really improve the look of a car. It is worth considering that altering your wheels and tyres can greatly affect the handling of a car. As a result, it’s best to only fit wheels and tyres that have been approved by the vehicle’s manufacturer.

When fitting new wheels and tyres, make sure there is acceptable clearance between the bodywork and the tyre. This allows for movement of the suspension and will prevent the tyres from rubbing on any bodywork which could cause the tire to fail.

Wheels and tyres that are deemed dangerous or illegal could land of fine of up to £2500 and 3 points PER TYRE / WHEEL. That means if all 4 are not legal then up to £10,000 fine along with 12 points.


low suspension

Lowering the suspension on car can help to improve the ‘sporty’ look, but the handling will be much stiffer and less comfortable.

Lowering of cars should always be carried out by a mechanic. Never simply remove parts of the suspension to make it lower as this is both dangerous and illegal.

As with changing the wheels and tyres, the clearance around the wheel and tyre needs to be considered to prevent rubbing of the tyre on the bodywork. Tyre rubbing can cause failure of the tyre and could land the driver with up to £2500 fine and 3 points per tyre.


twin exhaust

Changing the exhaust system can result in a noisier car. Some big-bore and aftermarket sports exhausts are not legal on UK roads as they are considered a nuisance due to the increased noise.

The catalytic converter on the exhaust system is a legal requirement no matter what exhaust is fitted to a car. It may be tempting to remove the cat to get a little more noise from the car but that will ensure the car fails its MOT and means the car is not roadworthy, so a prohibition notice may be issued for the car if discovered by the police.

Any exhaust which are deemed excessively noisy could receive a £50 fine combined with a prohibition notice to have the car taken off the road until the offending exhaust is replaced.

Engine enhancements

air filter modification

The list of possible engine enhancement is almost endless, depending on the car. From completely rebuilding the engine to changing a few components, extra horse power can be squeezed out of most engines in one way or another.

The legality of each enhancement should be checked to ensure that the car remains both legal and roadworthy. At Motorvation Bedford, we can check and advise you of how to get the most out of your engine and remain on the right side of the law.

Finally, remember…

Making modifications to a car may improve its look or performance, but they should never be made at the expense of safety. The law is there to ensure that cars on the road are safe for the driver, other road users and pedestrians, so please ensure that laws and regulations are followed.

Don’t put aesthetics ahead of safety or legality and tell the car’s insurer of any modification that have been made! If you’re in Bedford and looking to modify your car, give Motorvation Bedford a call, we can help to ensure your modifications are legal and safe for you and everyone else on the road.