Brakes, ABS

Wheels, Tires, Brakes

: Nissan Leaf


The LEAF has conventional hydraulically operated friction brakes. Additionally, the LEAF’s electric motor provides regenerative braking.
The hydraulic brakes is electrically assisted. Nissan LEAF Service Manual, BR-10 – BR-13
An internal motor operates a piston in the master cylinder to generate assist force.
A brake pedal stroke sensor detects the amount of brake pedal operation and signals the “electrically-driven intelligent brake unit” (IBU).
The IBU performs cooperative control of the regenerative brake and friction brake according to brake pedal travel and amount of cooperative regenerative brake control.
A pressure sensor in the master cylinder informs the IBU which increases or decreases brake assist so pressure inside the master cylinder equals a “target pressure”, derived from amount of brake pedal movement.
Cars with internal combustion engine . Since the LEAF does not have an internal combustion engine, an electric pump provides additional hydraulic pressure and acts as the brake booster Nissan LEAF Service Manual, section BR, page BR-11.. In the event of power loss, a large capacitor (called a “brake power supply backup unit”) provides stored electricity to power the pump The Nissan LEAF service manual, page BR-11. The brake power is described on page BR-11 under “Brake Power Supply Backup Unit”. Its exploded view is on page BR-223..
Here is a pic of the capacitor (“brake power supply backup unit”):

Here is a pic of the Toyota Prius’ brake back-up power capacitor assembly:

  Rotor Caliper
Type Diameter Thickness
Front Ventilated 283mm / 11.14″ 28mm / 1.102″ Two-piston single-action caliperNissan LEAF Service Manual, BR-240
Rear Ventilated 292mm / 11.5″ 16mm / 0.63″ Single-piston single-action caliperNissan LEAF Service Manual, BR-240

Parking/ Emergency Brake


  • To apply the parking brake while stationery, step firmly on the brake pedal and pull up on the parking brake switch to engage the parking brake. Pull up twice to apply maximum parking brake forceNissan LEAF Owner’s Manual, page 5-16..
  • To apply the parking brake while moving, pull up and hold the parking brake switch; when you release the parking brake switch, the parking brake will be released .
  • The parking/emergency brake can be applied while driving: pull up and hold the electric parking brake switch (page 5-16 of the ). A chime will sound. When you release the parking brake switch, the parking brake will be released. While moving, the parking brake is applied at a lower force than when stationeryLEAF Service Manual, page PB-20..

How The Parking/ Emergency Brake Works

The parking/emergency brake system consists of two drum brakes, one on each rear hubThe diagrams in the service manual (page PB-87) shows two cables, one going to each side.. The rear service brake’s rotor resembles a hat (5). The “crown” of the hat serves as the drum brake’s (2) housing. The drum brakes’ shoes are actuated by cables.
An “equalizer” (5) rides on a threaded shaft (4) and tensions both brake cables. An electric motor (1), operating from the 12V batteryNissan LEAF’s Owner’s Manual, page 5-16. drives the shaft via a reduction gear (2) and a clutch (3). The electric motor operates on signals from the parking brake control module, which receives signals from the parking brake button via the CAN bus. The emergency release (6) turns the reduction gear which turns the shaft which de-tensions the brake cables.

Here are a couple of pics of the parking brake’s cabling: pic 1 pic 2.


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