Originally Posted by jayadev
There would be slight skidding and some wheel locks intermittently as a part of balancing the brake distribution, 50-70 percent the car would remain in line of track.
if you compare same in a car without ABS
you will be shocked to see the brakes are more sensitive and responsive in such situations .
@jayadev: I think mercedised was mentioning this as part of how you would know if ABS
has been engaged and not whether it would be effective vis a vis non ABS
In summary, under loose gravel, snow etc. , non ABS
brakes would be more effective than ABS
ones (as pointed out by Jayadev). The reason is simple - the wheels will lock and you will be screeching and dragging the car on the road till it stops (thanks to coefficient of friction mostly and build up of material on front of your tyres). There will be tell-tale sign of rubber strips on the road behind you and smell of burnt rubber in your nose. Since wheels would be locked, you would be unable to steer and if there is a obstacle in front of you, you would be praying that your car stops before it hits it.
Some people do try to do a 'manual ABS
' in such cases -- trying to manually pump the brakes with their foot, but given that ABS
does it at a higher frequency (nearly 60 times per second), you will have to agree that the automated system if more efficient.
On high-traction surfaces such as bitumen, or concrete, many (though not all) ABS
-equipped cars are able to attain braking distances better (i.e. shorter) than those that would be easily possible without the benefit of ABS
. In real world conditions even an alert, skilled driver without ABS
would find it difficult, even through the use of techniques like threshold braking, to match or improve on the performance of a typical driver with a modern ABS
-equipped vehicle. ABS
reduces chances of crashing, and/or the severity of impact. The recommended technique for non-expert drivers in an ABS
-equipped car, in a typical full-braking emergency, is to press the brake pedal as firmly as possible and, where appropriate, to steer around obstructions. In such situations, ABS
will significantly reduce the chances of a skid and subsequent loss of control.
In gravel, sand and deep snow, ABS
tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS
prevents this from occurring. Some ABS
calibrations reduce this problem by slowing the cycling time, thus letting the wheels repeatedly briefly lock and unlock. Some vehicle manufacturers provide an "off-road" button to turn ABS
function off. The primary benefit of ABS
on such surfaces is to increase the ability of the driver to maintain control of the car rather than go into a skid, though loss of control remains more likely on soft surfaces like gravel or slippery surfaces like snow or ice. On a very slippery surface such as sheet ice or gravel, it is possible to lock multiple wheels at once, and this can defeat ABS
(which relies on comparing all four wheels, and detecting individual wheels skidding). Availability of ABS
relieves most drivers from learning threshold braking.
Hopefully the above helps.