Skip to main content
Cart, empty

Bosch braking

Bosch supplies the iBooster, the electro-mechanical unit that replaced the vacuum servo on many hybrid and electric vehicles. An engine that shuts off or never exists produces no vacuum, so the brake booster had to become an electric motor.

No engine, no vacuum, no servo

Power brakes on a petrol car run on engine vacuum. The inlet manifold provides it free whenever the engine turns, and a diaphragm in the servo multiplies the driver's effort. A hybrid that shuts its engine at every light, and an electric vehicle with no engine at all, have no such supply.

The iBooster replaces the diaphragm with an electric motor and a position sensor reading the pedal. It builds pressure on demand, and because it is commanded electronically rather than mechanically it can also apply the brakes without the driver — which is what an automatic emergency braking system needs to do.

It is also what allows regenerative braking to feel normal. The system blends motor braking and friction braking behind the scenes, varying the split continuously while the pedal under the driver's foot goes on behaving exactly as expected.

Bosch has engineered vehicle electrics from Stuttgart since 1886, and the iBooster is now in its second generation, fitted to vehicles from Tesla among others. Its pedal feel is generated deliberately by a spring and rubber simulator rather than by hydraulics, which is why the pedal stays consistent whether regeneration is doing the braking or the calipers are.

Checked

3 parts in our range