Tyres  /  Tyre News /  Help and Advice  / Can Worn Brake Discs Lead to MOT Failure?

Your car’s braking system plays a critical role in road safety – and it’s one of the key areas checked during the annual MOT test.

But can worn brake discs actually cause your vehicle to fail its MOT? Let’s explore everything you need to know about this mechanism and how it relates to your MOT.
 

Can Worn Brake Discs Fail an MOT Test?

Yes, worn brake discs can fail an MOT test. When a vehicle undergoes its MOT, the tester checks the braking system’s condition and performance. If the brake discs are worn below the manufacturer’s minimum thickness, it’s recorded as a major defect and will result in an immediate MOT fail.

Additionally, if the brake disc is loose, cracked, or dangerously compromised, it will be marked as a dangerous defect, meaning the car cannot be driven until it’s repaired.

In some cases, discs may be close to the limit and still pass, but they will be marked with an advisory notice, suggesting replacement soon.

Regular checks and timely replacements are crucial to avoid an unexpected fail.
 

How Worn Brake Discs Are Checked in an MOT

When you book your vehicle in for its MOT, the tester will carry out a thorough inspection of the braking system.

This includes checking the brake pads, discs, handbrake (or parking brake), brake fluid, and warning lights like the ABS.

Brake discs, in particular, are checked for two main things:

• Thickness: Every brake disc has a manufacturer-specified minimum thickness. If the disc is thinner than this limit, it’s classed as a major defect and leads to an automatic MOT failure.
• Condition: Cracks, warping, or excessive scoring on the disc surface can also lead to a fail, especially if they affect braking performance or compromise safety.

Why Do Brake Discs Wear Down?

Brake discs naturally wear out over time, mainly due to the friction created every time you brake. Factors such as driving habits, vehicle weight, and environmental conditions (like road salt or moisture) can accelerate disc wear.

Typically, brake discs last between 50,000 to 80,000 miles, but this can vary significantly. Short journeys, heavy loads, or aggressive braking can shorten this lifespan. It's a good idea to have your brakes checked during routine services, especially if you notice signs of wear like vibrations when braking or a squealing noise.
 

Worn Discs and MOT Failure: What to Watch For

A worn brake disc becomes an MOT issue when:

• The disc is below its minimum thickness: The tester will measure the disc and, if it doesn’t meet the manufacturer’s specification, it’s an automatic fail. This is classified as a major defect.
• The disc is loose or damaged: A disc that’s not securely attached or shows visible cracks is classed as a dangerous defect. This means the car cannot be driven until repaired.
• The braking system's performance is compromised: Even if the discs aren’t quite at the minimum thickness, excessive wear or damage can result in the brakes failing the efficiency test, leading to an MOT fail.

You might not always spot these issues yourself, but if you feel a juddering or vibrating brake pedal, or hear grinding noises when braking, it’s time to have the system checked.
 

Advisory Notices for Worn Brake Discs

It’s worth noting that if your discs are close to the minimum thickness but still within spec, the tester may issue an advisory notice. This means they’re legal for now, but you should plan a replacement soon to avoid future failure.

Can You Avoid a Brake Disc-Related MOT Failure?

Yes – with regular checks and maintenance. Here’s how:

• Listen for warning signs: Noises, vibrations, or reduced braking performance are red flags.
• Check the dashboard: An ABS or brake warning light could indicate a deeper problem that needs attention.
• Inspect the discs: If you’re comfortable, you can look at the discs through the wheel spokes. Signs of excessive scoring, corrosion, or thinness suggest it’s time to consult a garage.
• Book regular inspections: Most garages will check your brakes as part of a routine service or a pre-MOT check. This can help catch issues before they become MOT failures.
   

Dealing With Worn Brake Discs: Avoid Stress With a Seamless MOT Pass

Brake discs are a vital part of your car’s safety system – and if they’re too thin, damaged, or loose, your vehicle will fail its MOT.

By staying on top of brake maintenance and acting on warning signs, you can avoid MOT failures and keep your vehicle safe on the road.

Remember, if your car fails its MOT with a major or dangerous defect, you cannot legally drive it (except for certain pre-arranged retests or repairs).

Regular servicing and a proactive approach to brake care can save you the hassle and expense of an MOT failure.