04/02/2018
The rear brake pedal on a motorcycle is a crucial component for rider safety and control, working in conjunction with the rear braking system. While often overshadowed by the more prominent front brake, the rear brake plays a vital role in modulating speed, stabilising the motorcycle during deceleration, and assisting in low-speed manoeuvring. Understanding its mechanics is fundamental for any rider looking to enhance their riding proficiency and ensure their machine is in optimal working order. This article will delve into the intricate workings of the rear brake pedal, its associated components, and the importance of proper maintenance.
The Basic Operation of the Rear Brake Pedal
At its core, the rear brake pedal functions much like its front counterpart, albeit operated by your right foot. When you apply pressure to the pedal, you initiate a chain reaction that ultimately engages the rear brake caliper, which then squeezes the brake pads against the rear brake disc. This friction is what slows the rotation of the rear wheel.
The pedal itself is connected via a linkage or cable system to the master cylinder. When you press the pedal down, it moves an internal piston within the master cylinder. This piston forces brake fluid through the brake lines, pressurising the system. This hydraulic pressure is then transmitted to the caliper at the rear wheel. The caliper contains pistons that are pushed outwards by the fluid pressure, forcing the brake pads to clamp onto the brake disc. The degree of pressure you apply to the pedal directly correlates to the amount of hydraulic pressure generated, thus controlling the braking force applied to the rear wheel.
Key Components of the Rear Braking System
To fully appreciate how the rear brake pedal works, it's essential to understand the other components that make up the system. These include:
- Rear Brake Pedal: The rider interface for engaging the brake. Its position and feel are critical for intuitive operation.
- Brake Lever/Pushrod: Connected directly to the pedal, this component transmits the rider's input to the master cylinder.
- Rear Brake Master Cylinder: This is where the hydraulic pressure is generated. It contains a reservoir for brake fluid and a piston that is actuated by the brake lever.
- Brake Fluid: A specialised hydraulic fluid that transmits pressure throughout the braking system. It's vital that the correct type of fluid is used and that it is kept clean and free from moisture.
- Brake Lines/Hoses: These are reinforced hoses that carry the pressurised brake fluid from the master cylinder to the caliper.
- Rear Brake Caliper: This unit houses the pistons that push the brake pads against the disc.
- Brake Pads: Friction material that contacts the brake disc to create stopping power.
- Brake Disc (Rotor): A metal disc attached to the rear wheel that the brake pads clamp onto.
The Importance of Pedal Free Play and Return
A critical aspect of rear brake pedal operation is ensuring it has the correct amount of free play and that it returns fully to its resting position once released. Free play refers to the slight amount of movement the pedal has before it begins to engage the master cylinder. This is essential for several reasons:
- Preventing Drag: Insufficient free play means the brake pads may be constantly in light contact with the disc, leading to brake drag. This can cause premature wear of the pads and disc, reduce fuel efficiency, and generate excessive heat, potentially leading to brake fade.
- Ensuring Full Release: When you lift your foot off the pedal, it should return smoothly and completely to its original position. If the pedal remains partially engaged, it can lead to the issues mentioned above.
- Protection Against Damage: As noted, during a drop or crash, the pedal can bend inwards, potentially jamming against the frame. If the pedal is not returning freely, it's a strong indicator of a problem that needs immediate attention. A bent pedal that continues to apply even slight pressure can have serious consequences for your ride.
Regularly checking that the pedal moves freely and returns to its start position is a fundamental part of motorcycle maintenance. This can often be adjusted via a mechanism at the master cylinder or linkage, depending on the motorcycle model.
Adjusting the Rear Brake Pedal
The height and feel of the rear brake pedal can often be adjusted to suit the rider's preference and riding style. This adjustment typically involves altering the length of the pushrod or linkage connecting the pedal to the master cylinder. Most motorcycles have an adjustment nut on the pushrod or a threaded linkage that can be rotated to either increase or decrease the pedal height and free play.
When adjusting:
- Ensure the motorcycle is on its centre stand or a suitable paddock stand for stability.
- Locate the adjustment mechanism. This is usually found where the pedal lever connects to the master cylinder pushrod or a linkage rod.
- With the locking nut loosened, rotate the adjuster to achieve the desired pedal position and free play.
- Measure the free play. Typically, you're looking for around 5-10mm of pedal movement before the brake light switch activates or resistance is felt. Consult your owner's manual for the specific measurement for your bike.
- Once adjusted, tighten the locking nut securely.
- Test the brake to ensure it engages smoothly and releases fully.
It's crucial to get this adjustment right. Too much free play can delay braking response, while too little can lead to brake drag.
Maintenance and Common Issues
Like any part of a motorcycle's braking system, the rear brake pedal and its associated components require regular maintenance to ensure optimal performance and longevity.
Brake Fluid Replacement
Brake fluid is hygroscopic, meaning it absorbs moisture from the atmosphere. Over time, this moisture can lower the boiling point of the fluid, leading to reduced braking performance, especially under heavy use (brake fade). It can also contribute to corrosion within the braking system. It is generally recommended to flush and replace the brake fluid every one to two years, or as specified in your owner's manual. This process involves bleeding the system to remove old fluid and air, and refilling with fresh, appropriate-grade brake fluid.
Checking for Leaks
Regularly inspect the brake lines, master cylinder, and caliper for any signs of fluid leaks. Leaks can compromise the hydraulic system's integrity and lead to a loss of braking power. Even a small leak can be a precursor to a larger failure.
Pad and Disc Wear
While not directly part of the pedal mechanism, the condition of the brake pads and disc is paramount to effective braking. Worn pads or a damaged disc will significantly reduce stopping power, regardless of how well the pedal and hydraulic system are functioning. Inspect pads for thickness and check the disc for scoring, warping, or excessive wear.
Spring Issues
The return spring for the brake pedal is essential for ensuring it snaps back into position. If this spring becomes weak or breaks, the pedal may not return properly, leading to brake drag. This is a relatively straightforward part to replace if it fails.
When to Seek Professional Help
While basic checks and adjustments can be performed by the rider, certain issues are best left to qualified motorcycle technicians. These include:
- If the brake pedal feels spongy or the braking performance is significantly reduced.
- If you suspect a leak in the hydraulic system.
- If the brake disc appears warped or excessively worn.
- If the pedal mechanism is damaged or bent and you are not comfortable performing the repair.
Frequently Asked Questions
- Q: What should the rear brake pedal feel like?
- A: The pedal should feel firm and responsive, with a smooth action. There should be a small amount of free play before you feel resistance, and it should return fully when released.
- Q: How often should I check my rear brake pedal?
- A: It's good practice to check your brake pedal's free play and return action before every ride, and to inspect the brake fluid level and pad wear regularly, as per your owner's manual recommendations.
- Q: Can I use the rear brake exclusively?
- A: While the rear brake is important, relying on it exclusively is not recommended. For most motorcycles, the front brake provides the majority of the stopping power. Using both brakes in combination provides the most effective and stable deceleration.
- Q: What happens if my rear brake pedal is stuck?
- A: If your rear brake pedal is stuck or feels stiff, it could be due to corrosion, debris, or a damaged component. This needs to be addressed immediately, as it can lead to the brake being partially or fully engaged, causing overheating and potential failure.
In conclusion, the rear brake pedal is a vital, though often understated, part of your motorcycle's braking system. By understanding its operation, performing regular maintenance, and addressing any issues promptly, you can ensure consistent and reliable stopping power, contributing significantly to your safety and confidence on the road.
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