The motoring experts at have put together their guide on the modifications motorists can and can’t do.

They’ve looked at the most popular, including louder exhausts and number plates and others like tinted windows, stretched tyres and neon lights.

They do stress it is important to check regulations prior to making any modifications to your vehicle to ensure any changes are within the law, and to only modify vehicles you own outright.

A spokesperson for said: “A car modification is a change made to a vehicle which improves how it looks and how it performs although not all changes are within the law.

“It’s worth checking before you go ahead and make any changes, and note that you should only modify vehicles you own outright. Leased cars should be returned in their original condition. Illegal modifications could see you slapped with a fine and in some cases, your vehicle seized.

Always remember to update your insurance company too. Failure to do so can invalidate your policy.”

Here is’s guide to modifications:

Number plates

There are rules around number plates – check guidelines around what’s legal and not. Custom made plates can only be supplied by a registered number plate suppliers.

Bigger and louder exhausts

These are one of the most common modifications but aren’t always legal. Filters and turbos are allowed but the car must pass an MOT emission test. Drivers caught with an excessively loud exhaust can receive a £50 on the spot fine and could have their car taken off the road until it’s removed.

Lowering suspension

A car can be lowered but it must not affect the height of headlights or steering. If you do have modifications made to the suspension, make sure a good mechanic does them.

Stretched tyres

This is when tyres are stretched to fit a wider wheel rim than it’s meant for. They’re not illegal but you will be breaking the law if they don’t comply with current regulations.


Popular modifications to brakes include bigger brake callipers and grooved, drilled or vented discs. Do get advice from the car manufacturer and supplier to make sure the brakes are suitable.


This must be securely fitted to the car and shouldn’t have any sharp edges or obstruct the driver’s view.


Playing music too loud can lead to a police warning. If that’s ignored, the vehicle or equipment can be seized.

Tinted windows

There are no restrictions when it comes to tinting the rear windscreen and rear side windows. The front windows must let a minimum of 70% light through and a minimum of 75% through the windscreen.

Neon lights

These are illegal so don’t even consider fitting them. They could be easily mistaken for an emergency vehicle or recovery vehicle. They can be fitted underneath a car although the tubing must not be on show.