good motorinG
Braking new ground
H. Kishie Singh

The ABS master cylinder

LAST time we discussed that oversized tyres may cause the ABS in your car to go awry. What is an ABS and what does it do? It is an abbreviation of the German anti-blockier system. Conveniently, it is translated into English as anti-lock brake system.

Earlier, the brake system worked on cars through a master cylinder. When the driver pushed down the brake pedal, the hydraulic fluid commonly known as brake oil was pushed through the brake lines to all four brakes. There was only one line or may be two from the master cylinder that served all four brakes on the four wheels.

Engineers knew that the hydraulic fluid would exert an equal pressure or force on all four brakes, be they discs or drums, to provide equal braking.

Therein lay its inherent deficiencies. Equal force, under some circumstances, was not ideally suited for efficient braking. For example, if you braked hard and there was gravel on the road, all four brakes working equally wouldn’t be the ideal thing. Again, if you left the road, two wheels could be on tarmac and two wheels on the kutcha. There would be unequal braking because of the unequal surface.

Two wheels could lock up and throw the car into a skid. Even if you were on dry tarmac and, in a panic stop, stepped hard on the brake pedal, the wheels would get locked. The minute the wheels lock, they lose traction, and the car is likely to skid. The steering would be ineffective and the car would keep going in the direction it was travelling. The driver would have little or no control over the car. Which is why it is recommended to pump your brakes. A rolling tyre provides traction with the road; a locked tyre does not.

It was to overcome this problem that the ABS was invented. It "pumps" the brakes for the driver. When the driver steps hard on the brake pedal, the brakes grab. Just as the brakes are about to lock, they release for a millisecond and grab again.

A brake release–brake grab cycle is initiated and the wheels never lock up, thus providing the most efficient braking for the car under all conditions. In fact, it provides a shorter braking distance.

ABS is a German invention by Bosch. The research and experiments started in 1930. It was first tested on trucks. Dunlop had the same system and applied it to the aircraft.

It was not till 1978 that in its electronic avatar, it found use in select passenger cars. In 1985, for the first time the entire range of Ford Granada Mark III cars offered the system to the public.

The manufacturer also makes it clear that under ideal conditions (dry tarmac, good tyres, good brakes) a skilled driver, read Narain Karthikeyan, could stop in a shorter distance than an ABS-equipped car with an average driver at the wheel.

The accompanying photograph shows the ABS master cylinder. The four separate hydraulic brake lines can be seen quite easily, one for each wheel. This is the four-channel ABS. It consists of the pump, controller, valves and the speed sensor.

When the pump is activated, the speed sensor reacts. The controller takes over and monitors the force via the valves on how much pressure to apply on each individual wheel. The result: perfect braking. No lock-up, no skidding, no drifting.

Happy motoring.