rec.autos.simulators

------------------------
PHASE 0 threshold, straight line braking. Start by braking hard (to
get the tires up to temp.) then modulate back to squeal;

PHASE 1 initial turn in. The front of the car usually needs to be
loaded to get it to turn in, which is accomplished by braking. Relax
the braking effort (to use some traction budget for turning), and turn
in, aiming to keep the squeal constant.
------------------------

I allways thought the optimal braking point was just before the tires
start to squeel, instead of having the tires squeeling?

Andre

I think you're right about the optimal braking point. But, if there's
no sound coming from the front wheels, how can you tell if you're
braking hard enough? I should have said, "brake until the squeal just
starts and then play around with the brake pedal to keep the squeal on
the threshold".

Sent via Deja.com http://www.deja.com/
Before you buy.

The tyres don't start to squeel at a set point, the part of the tyre that
starts
to slip gets bigger and bigger across the footprint of the tyre until the
whole footprint is slipping and you have total lock-up.  I think for dry
conditions, you need about 15% of the footprint slipping for optimal
braking.  I don't know how this translates to car simulators,
but GPL is pretty realistic, so I expect they have it modelled well.

You should probably be aiming for a quieter squeel as possible, but as
long as you can still hear it.  If you can't hear any squeeling, you aren't
braking hard enough.

Scott

Andre

I agree that you can archieve it with practice, but information could
help you understand and improve it faster. there are facts or 'rules' in
racing, which apply to every driver regardless of his driving style. and
I personally tried different braking techniques without really finding
out the 'perfect one'. therefore I'd like to hear about the experiences
of other drivers. as far as I observed it, the best braking is with the
tires squeeling just a little bit as ricardo and scott mentioned before.

Lio

Tadej

First thing of course is to get the brake balance correct.  Too far
forward and the front tyres will be locking up too early causing
sliding.  Too far back and the rear end will start moving about as the
back end locks up.

Well, I've just done a GPL session to figure out what I do during
braking - it's on such a subconscious level that I wasn't quite sure
just thinking about it off the top of my head - this is what I've
discovered.

I find that I slam on the anchors hard during each gear change and then
ease off slightly whilst between gear changes.  So it goes something
like this.  Slam on anchors and start to change down.  Once back in gear
ease off from hard braking and then back on again during next downshift
and so on.  There are odd times that I recall changing down 2 gears at
one time, but these are rare and would only happen when going from 5th
to 3rd.

Using this technique my braking is pretty good and it even allows me to
be competitive under braking into the Parabolica using GPL 1.0.
--
Peter Ives

Andre

It would seem to be a little different with straight-line braking.  Here the
tire is trying to slide straight ahead instead of sideways.  There's always
another contact patch right next to the current one.  In order to make the
tire squeal, you would have to either lock the wheel, or reduce the size of
the contact patch.  The only way to reduce the size of the contact patch is
to reduce the weight on the tire.  Whenever you're breaking, you're putting
more weight on the front tires and less on the rears.  This could cause the
rears to "squeal a little" without locking the fronts or having the car
slide noticeably.

Does any of this sound right?

I'm thinking that with a certain amount of weight on the tire, it maintains
traction.  As you lighten the weight, it has less traction, until it gets to
some point where it's slipping.  When you're cornering to the right, you
would have greater weight on the left side of each tire than on the right.
The right edge of each tread could be slipping a bit while the left edge is
maintaining grip.

In other words, the right edge is pregnant and the left edge is just drunk
without protection ;-)

Racing online with the help of......

Race Communications Association
Holodyne Engineering
Mystic Music
(have Your !!Name/Address!! placed here)

Just my $.02

Gene

Mike Barlow posted a link to some racing physics pages, great reading.
Check out chapter 10.

You are absolutely correct.  Assume you are braking in a straight line.
(This might be for acceleration, I can't remember which way around it
is)  The middle part of the contact patch is compressed and as that part
of the tire moves away from the middle of the contact patch, it starts
to slip.  If you are only braking lightly, it will only start to slip when
it
has more or less left the road, and you won't hear anything.  Under
heavy braking, but not lock-up, the tyre starts to slip earlier and
earlier, causing more sound, until the whole contact-patch is
slipping.

Someone must have an animation of this somewhere, as I'm sure
I'm not the only one who can't visualise it.

Scott