Re: Driving question- trail braking.

[Steve An <giulietta@xxxxxxxxxxx>]

Hi,

I'll take a stab... braking into the turn is called trail braking, invented
by Mark Donahue (I think). 

In most cases, like a 90 degrees, constant or increasing radius turns, you
want finish your braking and downshifting in the straight before you start
turning in. This is the classical method of braking, i.e. how Frere and
Taruffi would teach you to drive, gettting the most out of your tire's
adhesion. Think of the friction circle, if the limit of adhesion is 100%,
you can trade off braking/turning/acceleration, but you can not exceed this
friction circle.

The other time when you want to brake while turning or trail brake is, for
instance, if you are in a decreasing radius turn. In this case, if you do
all your braking in the straight, i.e. to slow down enough for the smaller
radius, tighter, latter part of the turn, you are going to be too slow in
the early part of the turn where the larger radius allows you to carry
higher speed (try Big Bend at Lime Rock).

The other case is in S turns (turns 2 and 3 at LimeRock) where you may want
some car directional rotation. 

On the streets, most people don't know how to brake, they  initially apply
the brakes lightly then increase the pressure and lock them up or the pump
the brakes furiously trying to emulate ABS systems. This a horrible habit
because the car will nosedive and lock up, i.e. very unpleasant for the
passenger. This is exactly the opposite of what you should do, think about
it, when the car is going fast, you need to apply more braking to slow it
down, after it slows down, you need to trail off the braking effort or you
will lock up the brake.  The correct method is to apply the brake firmly
until you sense lock  up then ease off and re-apply. This is called
threshold braking. And even if you don't threshold brake on the street, try
to apply more brake pressure initially and trail off, it makes the driving
experience much more pleasant for your passenger. This is what they teach
limousine drivers and what Mercedes is trying to develop with the brake
assistance system.


        - Steve.

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