#First car with anti lock brakes drivers#
Some people think that drivers of ABS-equipped cars use the ABS incorrectly, either by pumping the brakes or by releasing the brakes when they feel the system pulsing. There is much speculation about the reason for this. The study actually stated that although cars with ABS were less likely to be involved in accidents fatal to the occupants of other cars, they are more likely to be involved in accidents fatal to the occupants of the ABS car, especially single-vehicle accidents. It turns out that in a 1996 study, vehicles equipped with ABS were overall no less likely to be involved in fatal accidents than vehicles without. The Insurance Institute for Highway Safety (IIHS) has conducted several studies trying to determine if cars equipped with ABS are involved in more or fewer fatal accidents. But do they really prevent accidents? This is the true measure of the effectiveness of ABS systems. They prevent wheels from locking up and provide the shortest stopping distance on slippery surfaces. You can locate the speed sensor by looking for an electrical connection near the differential on the rear-axle housing.Īnti-lock brakes really do help you stop better. Usually there will be one brake line going through a T-fitting to both rear wheels. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. This system operates the same as the rear end of a three-channel system. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle.
This system is commonly found on pickup trucks with rear-wheel ABS. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness. The rear wheels, however, are monitored together they both have to start to lock up before the ABS will activate on the rear. This system provides individual control of the front wheels, so they can both achieve maximum braking force. The speed sensor for the rear wheels is located in the rear axle.
This scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. Some ABS systems can cycle up to 15 times per second. When the ABS system is in operation you will feel a pulsing in the brake pedal this comes from the rapid opening and closing of the valves. This gives the system maximum braking power. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. It can do this very quickly, before the tire can actually significantly change speed. The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It might take a car five seconds to stop from 60 mph (96.6 kph) under ideal conditions, but a wheel that locks up could stop spinning in less than a second. If left unchecked, the wheel would stop much more quickly than any car could. Right before a wheel locks up, it will experience a rapid deceleration. It is looking for decelerations in the wheel that are out of the ordinary.
The controller monitors the speed sensors at all times. We will discuss how one of the simpler systems works. There are many different variations and control algorithms for ABS systems. It watches the speed sensors and controls the valves. That is what the pump does when a valve reduces the pressure in a line, the pump is there to get the pressure back up. Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. In position three, the valve releases some of the pressure from the brake.
#First car with anti lock brakes driver#
This prevents the pressure from rising further should the driver push the brake pedal harder. In position two, the valve blocks the line, isolating that brake from the master cylinder.In position one, the valve is open pressure from the master cylinder is passed right through to the brake.
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