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1、What are antilock brakes system? Antilock brakes are designed to help drivers avoid crashes. Without anti-locks, hard braking can cause wheels to lock, sending a vehicle into a skid. Wheel lockup can result in longer stopping distances, loss of steering control and, when road friction is uneven, los
2、s of stability if the vehicle begins to spin.The main advantage of anti-locks is that they can reduce these problems on wet and slippery roads. Anti-locks work with a vehicles normal service brakes to decrease stopping distance and increase the control and stability of the vehicle during hard brakin
3、g.The principle behind anti-locks is that a skidding wheel provides less stopping force and control than a wheel that is rotating. Anti-locks prevent wheels from skidding by monitoring the speed of each wheel and automatically pulsing the brake pressure on any wheels where skidding is detected. Anti
4、-locks dont make much difference in stopping distances on dry roads, although they can enhance vehicle stability and allow drivers to maintain steering control during emergency stops when conventional brakes might allow wheel lockup and skidding.How do antilock brakes system? Since most cars on the
5、road today have some form of Antilock Brakes (ABS) I think we should take a look at how they work and clear up some mis-information about them.As always, what I describe here is how most systems work in general. Since different manufactures have their own versions of ABS their values, specifications
6、 and part names will differ. If you are having a problem with the ABS on your vehicle you should always refer to the specific service and repair manuals for your vehicle.The ABS is a four-wheel system that prevents wheel lock-up by automatically modulating the brake pressure during an emergency stop
7、. By preventing the wheels from locking, it enables the driver to maintain steering control and to stop in the shortest possible distance under most conditions.During normal braking, the ABS and non-ABS brake pedal feel will be the same. During ABS operation, a pulsation can be felt in the brake ped
8、al, accompanied by a fall and then rise in brake pedal height and a clicking soundAnti-locks differ among vehicles, but there are some basic similarities. Each system has sensors that monitor the rotational speeds of selected wheels when brakes are applied. When one of these wheels approaches lockup
9、, a control unit reduces brake pressure to that wheel (or set of wheels) just enough to allow rotation again. This typically happens many times per second, resulting in improved control and, on many wet and slippery surfaces, shorter stopping distances.Differences among antilock brake systems includ
10、e the following:Cars and many SUVs have four-wheel systems with wheel-speed sensors on each wheel. In one type of system, the anti-locks reduce brake pressure to both rear wheels whenever one approaches lockup. Brake pressure to the front wheels of four-wheel systems is controlled independently to m
11、aximize stopping power, which is concentrated in the front. In four-wheel independent systems, each wheel is controlled individually, so when any one approaches lockup, the anti-locks reduce brake pressure to that wheel. Some pickups and cargo vans have rear-wheel-only antilock systems to address di
12、fferent braking needs when vehicles are loaded versus unloaded. The anti-locks monitor the rotational speeds of rear wheels only and release pressure to both when either is about to lock. Tractor-trailers have separate antilock systems for the tractors and the trailers. Ideally, both the tractor and
13、 trailer of a combination rig should have antilock brakes, but putting anti-locks on either component should produce improvement compared with conventional brakes. With anti-locks on the tractor only, a driver can maintain better steering control even if trailer wheels lock and the trailer swings. I
14、f only the trailer has anti-locks, trailer swing can be reduced even if steering control is lost. Why dont anti-locks reduce stopping distances as much on dry roads as wet ones?Adequate braking is easy to achieve on dry roads with or without antilock brakes. Even if wheels lock, the coefficient of f
15、riction between tires and road surface still is relatively high, so a vehicle stops relatively quickly. It is even possible on some surfaces to stop sooner without anti-locks than with them, although such instances are rare. They occur, for example, when loosely packed snow or gravel creates a dam e
16、ffect in front of locked wheels, shortening the stopping distance more than anti-locks could.Do car antilocks reduce crashes? Although car anti-locks perform well on the test track, it is unclear whether they have made significant reductions in the number of on-the-road crashes. A 1994 Highway Loss Data Institute (HLDI) study1 and a subsequent 1995 study2 compared insurance claims for groups of otherwise identical cars with and without anti-locks, find
