Motorcycle Brakes & Your MOT: A Comprehensive Guide

When it comes to motorcycle safety, few components are as critical as the braking system. Not only are perfectly functioning brakes essential for your personal safety on the road, but they are also a primary focus of the annual Ministry of Transport (MOT) test in the UK. Many motorcycles fail their MOT due to brake-related issues, making it vital for every rider to understand the stringent requirements and common pitfalls. This comprehensive guide will delve into the intricacies of motorcycle brake inspections, helping you ensure your bike is not only roadworthy but also passes its MOT with flying colours.

The Pivotal Role of Brake Controls in Your MOT

The MOT examination of your motorcycle's brakes begins with the controls themselves. The regulations are clear: your motorbike must be fitted with and have two independent methods of brake operation, both fully functioning. This typically means a front brake lever and a rear brake pedal, each controlling a separate wheel or system, or a linked system that adequately distributes braking force.

Beyond simply being present, these controls must meet exacting standards for security and operation. All controls, their mountings, and their fastenings must be absolutely secure and in good repair. Any looseness or damage here can immediately lead to an MOT failure. Furthermore, all pivots – the points where levers and pedals articulate – must exhibit reasonable levels of wear tolerance. Excessive play or stiffness in these pivots suggests wear that could compromise effective braking.

Crucially, all controls must be easy to apply, offering smooth and consistent action. There must also be adequate reserve travel on application, meaning that when you fully depress the lever or pedal, it shouldn't bottom out instantly. There should be a noticeable amount of travel remaining, indicating that the system isn't at its absolute limit of adjustment or worn beyond safe parameters.

For hydraulic systems, specific checks are performed to ensure optimal performance. The brake lever or pedal must not 'creep' under load. Creep occurs when you fully depress the brake lever and hold it firmly, but over time, its resistance diminishes, slowly allowing you to apply more and more pressure. This phenomenon is a tell-tale sign of a leak somewhere in the hydraulic system, compromising braking efficiency and safety. Similarly, the controls should not feel spongy when applied. A spongy feel often indicates air trapped within the hydraulic lines, which compresses under pressure instead of transmitting force directly to the calipers, leading to reduced braking power. Both creep and sponginess are immediate MOT failure points.

Detailed Inspection of Brake System Components

Once the controls pass muster, the MOT tester will meticulously examine the entire brake system. Every component is scrutinised for integrity, security, and wear. This section covers the common reasons why a motorcycle's brake system might fail the MOT.

Security and Integrity of Components

All security or locking devices, such as split pins, lock nuts, and circlips, must be present and secure. These small but vital components prevent larger parts from loosening or detaching under vibration and stress. Their absence or insecurity is a straightforward failure point.

Brake Pad and Lining Thickness

The thickness of your brake pads or linings is a fundamental safety check. There are specific minimum requirements:

• Standard brake pads or linings must be at least 1.5mm proud of their backing plates.
• Sintered brake pads or linings, often found on high-performance bikes, must be at least 1mm proud of their backing plates.

The difference in thickness requirements accounts for the different material compositions and wear characteristics of these pad types. Failure to meet these minimums means the pads are excessively worn and must be replaced.

Hydraulic Reservoirs and Fluid

For hydraulic braking systems, the fluid reservoir is critical. It must be securely mounted, properly capped, and sealed to prevent contamination and fluid loss. Crucially, it must also contain a sufficient level of brake fluid. Low fluid levels can indicate a leak or simply neglect, both of which impair braking performance and will result in an MOT failure.

Common System Failures and What to Look For

Beyond the specific checks above, a multitude of other issues can lead to an MOT failure:

• Cables, Levers, Rods, and Linkages: Any excessive wear, corrosion, cracking, or other damage to these mechanical components will be a fail. They must operate smoothly and freely.
• Drums or Discs: Insecure or cracked brake drums or discs are extremely dangerous and will immediately fail. Missing securing bolts for these components are also unacceptable.
• Free Play: Too much free play on levers or pedals, whether due to wear or poor adjustment, reduces braking effectiveness and indicates a problem.
• Contamination: The presence of oil or grease on brake pads or linings is a severe issue. Contamination drastically reduces friction, rendering the brakes ineffective.
• Mounting Insecurity: Insecure backing plates, reaction brackets, or calipers pose a significant risk and will result in a fail. All components must be rigidly mounted.
• Leaks: Leaking master cylinders or brake pipes/hoses are critical failures. Any visible fluid leak from the braking system means a loss of pressure and potential brake failure.
• Pipe Routing: Brake pipes that can be easily fouled or trapped by other moving parts of the motorcycle are a hazard and will fail. They must be routed safely away from potential interference.
• Pipe Support: Inadequately supported rigid pipes or hoses can vibrate, chafe, and eventually fail. All rigid lines must be properly secured.
• Hose Condition: Excessively chafed, twisted, or kinked brake pipes or hoses are a fail. While damage to protective sleeves alone might not fail an MOT, cracking or chafing severe enough to expose the hose reinforcement will.
• Disc Condition: Brake discs are checked for scoring, pitting, or excessive wear. Deep grooves or uneven surfaces reduce braking efficiency.
• Disc Run Out or Distortion: Excessive brake disc run out or distortion is a common failure. Run out is detected by a slight pulsing sensation when you lightly apply the brakes while the bike is moving. This is caused by warped or uneven wear in your motorbike’s discs. Even slight distortion can lead to inconsistent braking and reduced performance.

Special Notes on Hoses and Floating Discs

It’s important to note that damage to the protective sleeves of brake hoses will not necessarily lead to an MOT failure, provided the pipe or hose underneath is not damaged. The cracking or chafing must be severe enough to expose the hose reinforcement to be considered a fail.

Additionally, many modern sports motorcycles feature 'fully floating' discs, which are designed to have a certain degree of movement. If you observe some movement in your disc, do not immediately assume it’s an MOT fail. If in doubt, consult a qualified motorcycle MOT test technician, as they can accurately assess whether the movement is within acceptable design tolerances.

Brake Performance: The Ultimate Test of Efficiency

Beyond the physical inspection of components, the MOT includes a critical performance test of your motorcycle's brakes. This is where the actual stopping power and consistency are measured.

Indicators of Performance Failure

Several issues related to how your brakes perform can lead to an MOT failure:

• Sticking or Binding Brakes: If brakes do not fully release after application, causing drag, this is a dangerous condition and a fail.
• Severe Grab or Judder: A severe grab or judder during braking indicates serious problems, often with warped discs or contaminated pads, and will fail the test.
• Inconsistent Braking Effort: The braking effort should be consistent with the amount of pressure applied at the lever or pedal. Any inconsistency suggests a problem within the system.
• Excessive Fluctuation: When steady pressure is applied, there should be no excessive fluctuation of brake effort. Consistent braking force is key to safe stopping.

Braking Efficiency Requirements

The MOT specifies minimum braking efficiency levels that your motorcycle must achieve:

• At least one brake (typically the front) must achieve 30% efficiency.
• The other brake (typically the rear) must achieve at least 25% efficiency.

Efficiency is calculated by the motorcycle MOT computer system using a specific formula: Efficiency (%) = (Retarding Force ÷ Weight) x 100. The total retarding force is measured using a VOSA-approved brake tester, and 'Weight' is the combined weight of the motorbike plus the motorcycle MOT test technician. In the case of linked or dual braking systems, the retarding force is the total from both wheels when operated by the dual control only.

Modifications and Historical Exemptions

It's important to be aware of how modifications can affect your MOT. The VOSA handbook states that an MOT certificate should be refused if any deliberate modification has significantly reduced the original strength of a load-bearing member or its supporting structure. This applies to brake components and their mounts. While cosmetic modifications are generally fine, anything that compromises the structural integrity or safety of the braking system will lead to a failure.

Interestingly, motorcycles registered before 1st January 1927 have a specific exemption regarding braking systems. These pre-1927 motorcycles only need to have a braking system that works on one wheel, not both, reflecting the simpler engineering of their era.

Proactive Maintenance for MOT Success and Rider Safety

Passing your MOT is not just about compliance; it's about ensuring your safety and the safety of others on the road. Regular, proactive maintenance of your braking system can prevent most common MOT failures and keep you riding confidently.

Key Maintenance Tips:

• Regular Visual Checks: Make it a habit to regularly inspect your brake pads for wear, check fluid levels in reservoirs, and look for any signs of leaks around calipers, lines, and master cylinders.
• Fluid Checks and Changes: Brake fluid is hygroscopic, meaning it absorbs moisture over time, which can lead to reduced braking performance and internal corrosion. Check fluid levels frequently and consider flushing and replacing your brake fluid every one to two years, as recommended by your manufacturer. This can also help address sponginess.
• Bleeding Brakes: If your brakes feel spongy, you likely have air in the system. Bleeding your brakes correctly will remove this air, restoring a firm lever/pedal feel and full braking efficiency.
• Cleaning: Keep your brake components clean. Dirt and road grime can accelerate wear and, more critically, oil or grease contamination on pads can render them useless. Use appropriate brake cleaner if needed.
• Check for Free Play: Regularly check the free play in your brake levers and pedals. Adjust as necessary according to your bike's service manual to ensure optimal response without excessive slack.
• Disc Inspection: Periodically check your discs for scoring, pitting, or signs of warping (run out). If you notice any pulsing or inconsistency, have them inspected by a professional.
• Hose and Line Integrity: Inspect brake hoses for cracks, chafing, bulges, or leaks. Ensure rigid lines are securely clamped and not rubbing against other parts of the bike.
• Professional Servicing: Even if you perform regular checks, it's wise to have your braking system professionally inspected as part of your bike's routine service. Technicians can spot issues you might miss and have the specialist tools for more in-depth diagnostics.

Frequently Asked Questions About Motorcycle Brakes and MOT

Do motorcycles need two braking systems for an MOT?

Yes, generally. Motorbikes must have two independent methods of brake operation fitted and functioning, typically one for the front wheel and one for the rear. The only exception is for motorcycles first registered before 1st January 1927, which only need a braking system on one wheel.

What is 'brake creep' and why is it a problem?

Brake creep is when you fully depress a hydraulic brake lever or pedal, and its resistance slowly diminishes over time, allowing the lever/pedal to move further. This indicates a leak in the hydraulic system, leading to a loss of pressure and reduced braking effectiveness, which is an MOT failure.

How thick do my brake pads need to be for an MOT?

Standard brake pads or linings must be at least 1.5mm proud of their backing plates. For sintered brake pads or linings, the minimum thickness is 1mm proud of their backing plates.

Can cosmetic damage to a brake hose fail my MOT?

Not necessarily. Damage to the protective sleeves of brake hoses will not fail the MOT provided the actual pipe or hose to which it is attached is not damaged. Cracking or chafing must be severe enough to expose the hose reinforcement to be considered a fail.

What is 'run out' and how does it affect braking?

'Run out' refers to the wobble or unevenness of a brake disc as it rotates. It's often felt as a slight pulsing through the brake lever when lightly applied. Excessive run out is caused by warped or uneven wear in your motorbike’s discs, leading to inconsistent braking effort and reduced efficiency, which is an MOT failure.

How is braking efficiency calculated during an MOT?

Braking efficiency is calculated by the MOT computer system using the formula: Efficiency (%) = (Retarding Force ÷ Weight) x 100. The retarding force is measured by a VOSA-approved brake tester, and the weight is the combined weight of the motorbike and the MOT test technician.

Conclusion

The braking system on your motorcycle is a complex and vital assembly, playing a dual role in your safety and your bike's legal compliance. Understanding the detailed MOT requirements for brakes – from the functionality of controls and the integrity of components to the ultimate test of braking performance – is essential for every rider. By performing regular checks, addressing issues promptly, and adhering to the specified standards, you can ensure your motorcycle is not only safe and reliable on the road but also ready to pass its MOT with confidence. Don't underestimate the importance of well-maintained brakes; they are your first line of defence in an emergency and a non-negotiable aspect of responsible motorcycling.

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