rec.autos.simulators

Please repost!

Thanks,
    -Phasor

See Below

See other post

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repost of response to r.a.s. post of 16th Jan 2001
" Do real race car drivers stay on the throttle when Braking ???? NO!"
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Well, I think it's very clear that you can do some things in GPL that
a) wouldn't work in real-life and b) if they did would have major
impact on tire adn brake wear.

Your definition of trail-braking is perfect, however, to trail-brake
into a fast (>80mph) corner you must have some gas on so as
to keep the rears from going really light, losing traction  and
sending the car into oversteer.

I'm not sure I fully understand that. Certainly you are not altering
the brake bias, that is fixed in GPL Most formula cars in real-life
do have***pit brake-bias adjusters however.

What you are doing by providing power to the rear wheels whilst
braking is altering the weight balance under braking. If the weight
of the car stayed as it was at rest with more weight over the
rear tires you would set brake balance more rearward. You may
add a few extra clicks rearward as well as you have a greater
contact patch at the rear.

Howver, under throttle off braking the weight is shifted dramatically
foward, so we need to give the brakes a more forward bias, plus it
is always preferable for fronts to lose traction fractionally before
rears (although we don't want either of course).

This means we are braking much more with our skinny frint-tyres
than the wide rears. By providing power to the rears we shift the
weight balance under braking more rearward, hence we need to move
our brake balance more rearward to compensate.

We in effect get a greater braking force which, although it has
to brake more (as we are still pushing the car forward with
power) does in fact provide overall, a greater degree of
retardation. Theres a whole load of factors that go into this, but
GPL cars would I suspect, by nature of their realtively poor brake
performance and disparity between front and rear tire contact patches,
benefit greatly from this.

I should stress that we are talking partial throttle here, probably no
more than 25% as suggested in another post.

I've used this myself in single seaters, specifically Formual Ford,
Vauxhall Junior and Vauxhall Lotus but more for it's other benefit
of stabilising the car under heavy braking. With very little weight
on the rears any inblance in the car is likely to "wag the tail".

Especially noticable on the FF/FVJ as these where wingless
car (as GPL of course). The FVLs where winged cars and I
probably didn't need to do this, but perhaps did it out of habit

The lower the cars CoG (centre of gravity) the less of a problem
this forward movement of weight is under heavy braking (I'm sure
theres a formula for this) so with aerodynamic, very low sling modern
formula cars I doubt this is an issue.

It has an added benefit in GPL, assuming you left-foot brake
(the above was done using heel & toe) in that it allows you to fine
tune your corner entry speed a little better. If you do brake with
a little gas, if you brake a little late you can come off (the gas)
just before the turn-in point and get a little extra retardation, thus
still make the corner cleanly. If you brake a little early you can
give it a little more gas, keeping you speed a little higher so as
the enter the corner at the optimum speed.

This is MUCH more preferable to coming off the brake earlier
or backing off the brake as a) it's more difficult to do and
b) you'll take weight away from the front which will compromise
front-end grip, which you need for corner entry, so you'll wash-out

Argh! this has turned into another lecture, I knew it was fatal
to start responding.

In Summary, YES gas+brake is used in real life and B) I do
think (but don't know) that the GPL Physics engine is flawed
in the way it responds to very heavy simultaneous use of
gas + brake.

Oops theres more :
See above. Brake fade would be really interesting.

What Cars pez? where?

Maxx

See above.

Carl,

Can't say I've tried flooring the brake but counter-steering is a very
valid technique in real-life and in sim driving. I wrote a piece on
this recently for the VROC-F2 mailing list, so rather than do it
again I'll post that below.

As it says, this topic was covered pretty well in r.a.s. a while back
the post where under the title "N4 Steering and slides" posts
were between 24.12.00 to 30.12.00

I also posted an example GPL replay here, which was just 48k
(yes, I know we shouldn't post binaries, but it was very small
and many don't have access to the binary newsgroups).

It didn't get any complaints so if anyone wants me to post
it again then let me know, or drop me a mail removing the

Anywhere, here is the post.

My example shows the technique in operation also, but with variations
to keep the balance through the corner. Like all things it's a
question of degree, what you see in my clip and the "Full Lock" are
IMO perfectly normal and that's certainly how something like a modern
Formula Ford car would behave. Also you will often see saloons doing
this, especially inwet, also the best examples are Rally Cars and
Outlaw Sprint Cars.

I say it's a valid technique, it is in Outlaw cars and Rallying but
is not something you'd try and provoke on a circuit but a technique
you'd use to catch a slide once you've got beyond the state where
opposite lock will save it.

I have heard it said that you can also catch slides that under normal
"real-life" situations, you wouldn't be able to, but I've not seen
this myself.

This thread carried on longer and in more detail in the newsgroups
rec.autos.simulators and we did try and explain what was actually
happening. The consensus was (and it makes very good sense) is that
by doing this you reduce the grip available to the front tires (by
nature of increasing the slip angle which has the effect of lessening
grip).

The car is oversteering because you have a higher slip-angle (less
grip) available at the rear than the front, so by doing this you are
helping to balance this out by reducing the front-end grip, hence the
car drifts sideways, slows and eventually grip is returned to both
ends of the car.

It's not a natural reaction however so you may never use it yourself,
but it is worth practicing as it will keep you on the track in
situations where you would normally spin.

Maxx

Someone also posted this quote although neglected to mention
where it was from :

"A vehicle oversteers because the slip angle of the tires at the rear
is increasing faster than the slip angle of the tires at the front of
the vehicle.  Increasing the the slip angle on the tires at the front
of the vehicle can equalize the slip angles and negate the oversteer
condition although it does little to control the vehicle's
trajectory.  In real life this can cause elevated tire temperatures,
resulting in reduced grip, and negatively effect the tire's life span"

FINAL NOTE:

Flooring the brake will have the same effect, i.e. reducing front
end grip, so this may work as well, but you can often counter
steer out of a slide and lose very little time.

Maxx

I'm just behind the 1:08 cars to the 2'nd 90deg turn at A1-ring.
There I loose much grounds while accelerating.
I did 1:10:999 best.

I often loose the rear end in very tight corners,
like 1st, 2nd at A1 ring, and the tight right-downwards turn at Nurburgring.

I think I'll practice not letting go of the throttle.

How about setups?
What is most beneficial to poke with, if I drive 'pushing' in long corners,
and use 'trottle-braking'?
I find thight corners and accelerating the biggest problem.

Thank you for your excellent explanations!

/Carl

/Carl

Strange, when I drive there is always one of the Ferraris all over the place
;-)

[This bit was written thinking i was talking about GPL]

Well, I should say first that I rarely run F1 these days as I just
don't have the time. As I run in F2/FD leagues they take up
most of my time.

I personally never run more than 53% and often run as low as 50%.

[This bit is not sim specific]

You'd think that, as the rear wheels of the cars are wider, hence
have more comparable grip, that the brake balance should be
more rearward but in fact grip is not just a function of tire patch,
it also has to do with weight being applied.

Under braking the vast majority of the weight of the car is over the
front wheels, so it actually works out that you need more front
bias for even braking. Also, if you are ever to lockup under braking
it's better that the fronts do rather than the rears.

Anyway, as I said before, what we are doing by applying some
gas is trying to move the weight that little bit further back, so we
can benefit from those wider tires.

In truth the main reason for doing this in real-life and to a large
degree in sims is to prevent fishtailing under heavy braking.

I'm still not sure whether you get improved BRAKING by
having a little power on, I suspect not so much in real-life
maybe the way the sim works means you do in the sim.

What I am sure of in real-life and in GPL (thats about the
only thing I run) is that you can brake harder without getting
instability (i.e. fishtailing).

The reason for this is that what is happening under very
heavy brakes is that there is so much weight forward that
there is very little grip at all at the rear, any slight twitch by the
driver, as an effect of camber settings or uneven tire temps
etc. can cause "a moment" which will often mean the driver
will brake less hard the next time around.

The whole braking dynamic changes with Aero cars, as
the slower you go the less grip you have (as the aero
downforce decreases), so in real-life you  have to ease back on
the brake.

I doubt that this level of modelling is done in any of the
current crop of modern F1 sims so I wouldn't get too concerned
yet.

I wouldnt try and guage my driving by any measure of
the AI, in any sim. The AI will IMO not be running the same physics
as your car. Certainly this is the case with GPL and I would have
thought that all sims would use a rather simplified model.

I could be wrong, my only real experience is with GPL.

The most common cause of losing the rear is not providing
a balanced throttle through the corners.

The gas and brake pedals are somewhat more useful than just
accelerating and braking the car, they are in fact "tire grip"
modifiers. In general the brake will add front end grip, the gas
pedal (up to a degree) will add rear grip.

What you therefore need during most cornering is a balanced
throttle, neither accel not decell, which will keep more weight
over the rear tires, giving you more grip, hence no spin.

Modern F1 sims don't really allow you to expericence this
delicate balance but in GPL, to go quickly you will be sliding
through every corner. You "control" that slide by very slight
variations in throttle application, sometimes brake but not so
often.

Cant help you with F1RC, AFAIK there are these "magic" techniques that
work with modern F1 sims that are not what would work or be practiced
in real-life. But I can't help you with those I'm afraid as I don't
run them.

I think that if you view the application of gas as a means to
stabilise the car under heavy braking and use no more than say 20-30%
and more at the end of braking than at the beginning (for an aero car)
you would be doing something with some validity in real-life.

Your welcome. I hope I've not gone overboard with the above, but
it's interesting stuff.

I'll try working on A1 this weekend

    -Phasor

Thanks for the info Maxx, great stuff.

    -Phasor

yep.. trail braking to transfer weight to the front wheels to get them to
bite again.

KK

well... one major problem with sims is they don't take flat-spotting into
account... in F1, locked brakes is very quickly followed by an in-lp for a
change of tyres.... the ensuing vibration at high speeds can do very bad
things (delamination?)

KK

the fundamental difference though between GPL-spec cars and modern F1s is
that there is still a surprisingly large amount of force applied under
braking by the rear wheels due to the rear wing... which generates about
300kg more downforce at speed than the front.... couple that with minimal
suspension movement and low CoG (and consequently a lower moment of inertia
under braking)... and the rears are doing a lot of work.... hence you see
the inside front light up long before the rears under heavy braking

KK

Argh! don't get me started on Engine Braking, again I did a long piece
on this a while ago. I've heard that in games like GP3 this works
"too" well. It is a valid technique if applied properly and although
referred to as Engine Braking I prefer to call it "Optimum Downshift
Under Braking".

If you lift off (no brakes) at 10,000 revs the car will slow down much
more than if you lift off at say 5,000 revs. So to use ODUB you would
downshift such that when the car went into the next lower gear, it
did so at somewhere just below max revs, thus getting some added
benefit from "engine braking", also this braking is applied to the
rear wheels which we have already said is beneficial.

Obviously you should not change down into a lower gear if it
means that once engaged the engine will be forced to rev
above max revs, this is Engine "Breaking" but I think you
can probably get away with that on many modern F1 sims,
and as you have found, it probably gives you exaggerated
stopping power.

You certainly can't do it in GPL or N4, or of course in real-life.

Maxx

KK

/Carl