On 10/31/2013 7:57 AM, H. S. Teoh wrote:
You don't know how thankful I am for having learnt the concept of
pumping the brakes, ABS or not. I'm afraid too many driving instructors
nowadays just advise slamming the brakes and relying on the ABS to do
the job. It doesn't *always* work!
Pumping the brakes is not how to get the max braking effect.
The way to do it is to push on the pedal to about 70-80% of braking force. This
causes the car to push its weight onto the front tires and load them up. Then go
100%. You'll stop a lot faster, because with more weight on the front tires they
have more grip. (I think this is called 2 step braking.)
You lose about 30% of braking force when the tires break loose. The trick is to
press the pedal just short of that happening, which can be found with a bit of
practice.
The downside of just slamming the brakes on and letting the ABS take care of it
is you lose the 2-step effect.
There are also cases where you *want* to lock the tires. That case is when
you're in a skid and the car is at a large angle relative to its velocity
vector. This will cause the car to slide in a straight line, meaning that other
cars can avoid you. If you don't lock the wheels, the wheels can arbitrarily
"grab" and shoot the car off in an unexpected direction - like over the
embankment, or into the car that was dodging you. The car will also stop faster
than if the wheels suddenly grab when you're at a 30 degree angle.
But yeah, I'd guess less than 1% of drivers know this stuff. And even if you
know it, you have to practice it now and then to be proficient at it.
