When you must brake your car very quickly, why is it safer if the wheels don't lock?

Answer 1

If the wheels lock you change from the static to dynamic (sliding) coefficient of friction which is lower... which means a less substantial contact with the road lengthening stopping distance and reducing steerage.

Aloha

Answer 2

Wheel of a vehicle are able to move because there is friction between the wheel and the pavement.
Even though road friction slows down the vehicle it is not enough to stop a car when you want. So the breaking system was invented to perform the job. The breaking action is due to the friction beween the pads and the rotor disks on the wheels.
when the wheels lock there is no more friction on the rotor to absorb the motional energy.So the only fricftioin that occurs is the the tires scraping the pavement which have a slow braking action.Sometimes the sliding on the road may cause avoiding a collison with another car.

The anti lock brake system may work better on a wet road for inexperience driver who dont know how to pump the brakes.However when coming to an intersection especially if there is gravel the car will not brake but continue to travel with oscilating brakes and by the time the car finally stops you are in the middle of the road. thus collison with oncoming trafic.
So antilock brakes have a limitation when it comes to safety.
A better system needs to be developped.

Answer 3

Sometimes it's better to lock up all the wheels . It's just bad to only lock up some of the wheels.
When you're driving in the rain particularly, if you panic stop most people slide sideways or swap ends because they only lock up some of the wheels. Driving classes will actually teach you to slam on the brakes as hard as you can on wet roads, if you need to stop as fast as possible, so you'll lock up all four wheels at the same time, and come to a relatively straight stop. If you apply the brakes too gradually some wheels will lock up before others and send you into a slide.

Answer 4

If you brake the car quickly and lock the wheels, the part of the tire touching the road (the "contact patch") will stay in touch with the pavement and skid along. The friction and energy will melt part of the tire and the car will skid along on the slippery melted tire, eventually stopping.

If the wheel don't quite lock, then the tire continues to slowly rotate during a panic stop and the tire surface doesn't melt onto the pavement. Because a solid tire grips the road better than a melted tire surface, the car will stop in a SHORTER distance than if it were skidding along on melted rubber.

The car is easier to control and steer if solid rubber is touching the pavement instead of melted tire. So the slow rotation also adds the safety feature of controllability and steering.

Answer 5

because when the wheels are constantly moving and slowing down the car stops faster than if the wheels completely lock up and the car skids. Plus, you have more control over a car that is not skidding. For example, driving on an snowy road, if you start to skid you go farther than if you don't skid, and you lose control. Ice is the extreme, but this is applied to all driving conditions

Answer 6

Two reasons. (1) You stop faster. (2) You have more control.

This is because the static coefficient of friction (wheels not locked) is greater than the dynamic coefficient of friction (wheels locked - wheels are sliding on the road). You stop faster without locking up because you have greater friction between the tires and the road. This greater friction also allows you greater control and better ability to steer the car. When sliding, the car largely goes where it wants - you have almost no control.

Answer 7

If the wheels lock the car continues in whatever direction it was travelling before applying the brakes and steering will not change the direction the car is travelling.

Answer 8

When your wheels lock in place, your wheels no longer turn. If your wheels can not spin, then you cannot turn. You are able to retain more control of the situation when you don't lock your wheels and come to a controlled stop.

Answer 9

urbancoyote has it locked. (look further down)stability control is a standard on all Mercedes vehicles now and is growing in popularity, much more intelligent than standard ABS . But ABS equipped vehicles are by far a mile stone in safety on the road

Answer 10

the car is more likely to skid. better to use engine brake or tap a few times on the brake