Hydraulic Handbrakes
A hydraulic handbrake, also called emergency brake, e-brake, staging brake, or drift brake, is a braking mechanism used to keep a vehicle motionless and, in many cases, also perform an emergency stop. This braking mechanism uses brake fluid, typically containing glycol ethers, to transmit pedal force to the four brakes.
Originally, the hydraulic handbrakes were meant to stop a vehicle when the main brake system failed. Today, they are used to keep a car stationary when it is parked. Emergency brakes are also used in the sport of drifting, rallying, and autocrossing.
The hydraulic brake is far more powerful and faster than the standard cable brakes on the market. Its ability to lock up the rear tyres quickly makes it a valuable addition to a drifter set-up.
In rally racing, the rally handbrake is used to counter the understeer found in front-wheel drive cars competing in events.
In drag racing, it is used to enable burnouts and preload the driveline in order to absorb shock when the vehicle is launched from a dead stop.
While the hydraulic handbrake is part of the overall braking system, it is applied independently of the service brake. This handbrake is installed in-line with the existing brake system and is connected to the rear brakes.
Components of a Hydraulic Handbrake
A typical hydraulic brake has fewer components that the primary brake system. They include:
Intermediate lever – the lever is used to engage and disengage the parking brake. This component is held in position with a ratchet locking mechanism.
Steel cables – the cables connect the main brakes of the vehicle to the hydro-brake lever. They transmit the lever movement through a series of components to the brake assembly. The cable system has a “Y” design that allows several cables to be connected to the rear brakes. A separate cable is used to attach the equalizer to the lever of the vehicle.
Other components of the hydraulic handbrake are a pull rod, equalizer and adjusting nut.
Types of Hydraulic Handbrake Levers
There are different types of emergency handbrake levers. The application of each brake depends on the design of the driver’s seat and the desired operating effort.
Stick type lever – this lever is found under the instrument cluster and is common in older cars.
Centre lever type or pull handle – the centre lever is located between the two front seats of a car, near the console of new car models.
Pedal type – this is located on the left side of the floor-hinged pedals.
Electric or push button – the electric lever is located on the centre console and is common in new car models.
How Hydraulic Handbrakes Work
When the emergency handbrake is engaged, the cable attached to the hydraulic handbrake rotates the intermediate lever anticlockwise. The crank pin then moves the strut to the left causing the sleeve nut, adjusting bolt and piston to move towards the left. The movement of the strut also compresses the adjusting bolt return spring. The force generated then passes through the U-shaped equalizer. The equalizer divides the force and sends it evenly across the two cables connected to the main brake system.
When the handbrake is disengaged, the compressed return spring punches the caliper piston and the bolt back to their previous positions. Consequently, the hydraulic handbrake is released. When the handbrake is disengaged, the clutch prevents the sleeve nut from rotating, transferring the force of the lever to the caliper piston through the adjusting bolt.
This operation applies to vehicles that use disc brakes on all the four wheels (most common brake configuration). Vehicles with a rear drum brake system (rare on new car models) have the hydraulic handbrake cables running directly to the rear brake shoes. These vehicles often have a more complicated hydraulic brake system called an exclusive handbrake.
The shoes and other components of the exclusive handbrake are similar to those of a drum brake but smaller and with no wheel cylinder. The system also has an additional corkscrew and lever added to the existing caliper piston. When the handbrake is activated, the lever forces the corkscrew against the piston, activating the brake.
System Limitations
Corrosion – the race handbrake can corrode if they are not engaged on a regular basis. This is particularly common for the shielded cables as they are vulnerable to dirt, debris, salt and other agents that may cause corrosion. A simple solution to this problem is to use the hydraulic handbrake regularly.
Breakage and malfunctions - a car’s brakes are controlled by a parking pawl, a device that locks up the transmission when the car is put in park. As with any part of a car, the parking pawl can break or malfunction. Additionally, it can wear out from constant use.
