It's Not Just a Visual Check
Unlike some MOT items that are assessed visually, brakes are tested using a roller brake tester — a machine that spins each wheel and measures the actual braking force applied, rather than relying on the tester's judgement alone. This gives an objective, repeatable measurement of how well your brakes are performing.
What the Machine Measures
- Braking efficiency — the overall stopping force generated as a percentage of the vehicle's weight
- Imbalance between wheels — brakes on the same axle must perform within a set percentage of each other; excessive imbalance suggests uneven wear, a sticking caliper, or a hydraulic fault
- Handbrake performance — checked separately to confirm it can hold the vehicle on its own
Visual Brake Checks
Alongside the machine test, the tester also visually inspects brake components for:
- Pad and disc wear beyond the minimum thickness
- Fluid leaks from callipers, pipes or hoses
- Corroded or damaged brake pipes and flexible hoses
- Warning lights relating to the brake or ABS system
- Correct operation of the brake pedal and handbrake lever or button
Common Reasons Brakes Fail an MOT
- Pads or discs worn beyond the safe minimum
- Uneven braking force between left and right wheels on the same axle
- A handbrake that doesn't hold on the test incline
- Fluid leaks, often from a perished seal or corroded pipe
- Seized or sticking calipers, common on cars that have sat unused for long periods
Why brakes seize on cars that sit still: If a vehicle has been parked for long periods without being driven, brake components can corrode or stick — this is common on hybrid and electric vehicles where regenerative braking means the friction brakes are used less often. A regular drive helps keep them free.
Signs You Might Fail the Brake Test
- A grinding or squealing noise when braking
- The car pulling to one side under braking
- A spongy or soft brake pedal
- The handbrake needing to be pulled further up than usual to hold the car
- A visible brake warning light on the dashboard
If you've noticed any of these, it's worth having your brakes checked before you book your MOT rather than risking a failure. See our guide to dashboard warning lights if your brake or ABS light is showing.
Book Your MOT with Autoclinics High Wycombe
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