Are Drilled and Slotted Brake Discs Legal in the UK?

Legal

Drilled and slotted brake discs are legal in the UK as long as the brakes stay efficient and the discs are sound. They are a common upgrade; the only risk is that cheap cross-drilled discs can crack, which the MOT would fail.

Why?

The law does not care about the pattern on the disc face; it cares that the brakes work. The MOT and roadworthiness rules require braking to be efficient and balanced across each axle, and the discs to be free of significant cracks, scoring or wear. Drilled or slotted discs that meet that are perfectly legal.

The practical caution is quality. Slotted discs are generally robust; cheap cross-drilled discs concentrate stress at the holes and can crack under hard use, and a cracked disc is both dangerous and an MOT failure. Buying reputable discs sized for your car avoids that.

As with any brake change, tell your insurer. Choose good discs, keep them in condition, and there is no legal barrier to running drilled or slotted rotors.

What decides if it's legal

Braking must stay efficient and balanced side-to-side (the MOT tests this).
Use quality discs correctly matched to the car and pads.
The discs must be in good condition - no cracks, scoring or excessive wear.
Declare brake changes to your insurer.

Does it depend on your car?

Disc size and fitment are car-specific, and heavier or more powerful cars stress discs harder. The legal test - efficient, balanced brakes with sound discs - is identical for all.

Related legality guides

Find your car in the garage

Sources

This page is general guidance, not legal advice, on the rules in the UK for drilled and slotted brake discs. The detail varies by exact vehicle and changes over time - confirm with your insurer and the latest DVSA and GOV.UK guidance before modifying.