What Are Brake Cables?
Brake cables are critical components in vehicle braking systems, particularly for bicycles and motorcycles. They connect the brake lever (or pedal) to the brake mechanism, such as calipers or pads, enabling the vehicle to slow down or stop by transmitting mechanical force.
How Do They Work?
When you activate the brake lever, it pulls an inner steel wire through an outer housing, transmitting force to the brake mechanism. This action presses the brake pads against the wheel or disc, creating friction to slow or stop the vehicle. Tension can be adjusted using a barrel adjuster for fine-tuning.
Why Are They Important?
Brake cables are essential for safe braking, requiring regular inspection for wear, corrosion, or fraying. Proper maintenance ensures reliable performance, preventing issues like reduced braking efficiency or failure.
Introduction
A brake cable is a critical component in the braking systems of various vehicles, particularly bicycles, motorcycles, and some automobiles. It is a type of Bowden cable, which consists of an inner cable made of twisted steel wire and an outer housing, typically a helical steel wire with a plastic covering. The brake cable transmits mechanical force from the brake lever (or pedal) to the brake mechanism, enabling the vehicle to slow down or stop.
Definition and Composition
A brake cable is a flexible cable used to connect the brake control (e.g., brake lever on a bicycle or handlebar) to the brake mechanism (e.g., brake calipers or pads).
It is part of a Bowden cable system, named after its inventor, Ernest Monnington Bowden, and is widely used in bicycles, motorcycles, and some auxiliary braking systems in cars (e.g., parking brakes).
The cable comprises:
Inner Cable: A twisted steel wire that moves relative to the outer housing to transmit force, typically 1.5-1.6 mm thick for brakes to handle higher tension.Outer Housing: A protective sleeve, often made of helical steel wire with plastic liners, that provides resistance and guides the inner cable, ensuring smooth force transmission.Mechanism of Operation
- When the brake lever is activated (e.g., squeezed on a bicycle), it pulls the inner cable of the Bowden cable.
- This pulling action transmits force through the cable to the brake mechanism (e.g., brake pads or calipers).
- In bicycles, the inner cable pulls one arm of the brake (e.g., in a sidepull brake), while the housing pushes the other arm, creating a balanced braking force (Newton's principle of equal and opposite reactions).
- The cable's linear movement transmits pull force, and in some applications (e.g., aircraft throttle controls), it can also transmit push-and-pull forces.
- Tension in the cable can be adjusted using a "barrel adjuster," an inline hollow bolt that lengthens or shortens the housing relative to a fixed anchor point. Turning the barrel adjuster out lengthens the housing and tightens the cable, while turning it in shortens the housing and loosens the cable, allowing for fine-tuning of brake responsiveness.
Types and Applications
Brake cables are used in various contexts, each with specific requirements:
| Application | Description | Typical Use |
|---|
| Bicycles | Connects brake levers to calipers, activating pads against rims or discs. | Mechanical disc brakes, rim brakes. |
| Motorcycles | Often used for clutch or throttle, though modern bikes may use hydraulics. | Auxiliary controls, older models. |
| Automobiles | Less common in primary brakes, used in parking brakes for mechanical connection. | Emergency or auxiliary braking. |
- Bicycles: Brake cables are essential for mechanical disc brakes and rim brakes, where the cable activates the brake pads to press against the disc or rim. They must use conventional helical housing, as opposed to gear cables, which use compressionless housing for precise shifting.
- Motorcycles: Brake cables are often used for clutch or throttle controls, though modern motorcycles increasingly use hydraulic systems for brakes.
- Automobiles: Brake cables are less common in primary braking systems but are used in auxiliary systems like parking brakes, where they provide a mechanical connection independent of hydraulic systems.
Importance and Safety Considerations
- Brake cables are crucial for vehicle safety, ensuring reliable braking performance.
- They must be regularly inspected for wear, corrosion, or fraying, as failure can lead to loss of braking ability.
- Common issues include:
- Maintenance involves:
- For bicycles, it's recommended to carry spare cables during rides, as they can be repaired or replaced at the roadside with minimal tools (e.g., Allen wrenches).
Key Differences Between Brake and Gear Cables
To highlight the distinctions, here's a comparison table:
| Feature | Brake Cable | Gear Cable |
|---|
| Inner Wire Thickness | Thicker (1.5-1.6 mm) for higher tension | Thinner (1.2 mm) for lower tension |
| Housing Type | Conventional helical housing | Compressionless housing for precision |
| Purpose | Transmits force for braking | Transmits force for gear shifting |
| Fittings | Cylindrical or mushroom ends (e.g., for flat-bar or drop-bar levers, sometimes double-ended and cuttable) | Small cylindrical end, axis parallel to wire, or older side-exit types |
| Safety Note | Must use helical housing; index-compatible housing (e.g., Shimano S.I.S.) is dangerous for brakes | Can use index-compatible housing for precise shifting
|
