The most common road crash is a nose-to-tail impact caused
mainly by a lack of understanding of how to brake properly. We have
all seen or heard it and anyone who has been driving for any length
of time has probably experienced it first hand - the sickening
screech of tyre on road followed by a very solid thump. It's most
agonising to be in the stationary car at the front of the queue
watching Mr Inattentive about to inflict the front of his car on
you....
Being confronted with an emergency situation has one immediate
affect - it rapidly raises your heart rate about threefold and fear
takes control of your car. Understanding what is about to happen
when you jump on the brake pedal is the only way of being able to
calmly operate in this situation. A locked wheel will not stop you
as fast as a wheel that is rotating with a braking affect. In fact,
the best braking happens when the braking effort is being applied
to the point just before lock-up.
You only have to watch a racing car on a track to see this
first-hand - a lock-up mistake usually results in the car leaving
the track or at best running wide in a corner and losing positions
to other competitors. The other huge disadvantage of a locked front
wheel is that it renders the vehicle out of control. No steering
can take place if the wheel is not turning.
The most efficient method of stopping in an emergency is threshold
braking, also sometimes called cadence braking.
Threshold braking involves technique and feel. Squeeze the pedal
firmly so you get the feel of hanging in the seat belts as the
weight of the car transfers forwards. This puts more weight over
your front wheels - which is good, because it's the front wheels
that do most of the braking. Now that you have a higher grip level
to play with, all that is remaining is to keep an even and firm
pressure on the pedal over the remainder of the stopping
distance.
Knowing how hard you can press the brake pedal before the wheels
lock up can only be found out through experience. But you need to
understand this - if during an emergency stop you hear the ominous
sound of tyre squeal and start to smell smoke, un-squeeze the pedal
by a small amount to stop the lock-up and regain control! This is
where some finesse is required. Come off the brakes too much, and
your (so far) well controlled stop will suddenly speed up and
extend the stopping distance that you initially required...
The most important advantage of threshold braking is that it leaves
you in control and with the ability to steer around an obstacle. If
you let fear take control, the brakes will be jabbed hard not
giving time for any weight transfer and so locking the wheels. The
result is an extended stopping distance without the ability of the
driver to steer. It's for this reason that ABS (Anti-lock Braking
System) was invented.
