rec.autos.simulators

  I hope you won't mind me picking on the numbers a bit here :0)  Some Nascar
slick data shows a grip coefficient of about 1.2 at typical loads.  Decent
street tires run around .75-.85, with some good performance street tires up
around 1-1.1 or so.  1.7 would be on par with a lightly loaded F-1 or Indycar
tire probably (as you know from RCVD), still way too high for a Ferrari IMO,
but fun to drive anyway I'm sure.  When you get into numbers like 2.5 and up,
you're into 10 inch drag racing slicks (they don't work laterally that well
though, I don't think.)

  My guess for a Ferrari like this would be 45-55 cm.  Just for comparison, I'm
testing mostly with a 1590 Kg (3500 lb) car, with approximately 60 cm center of
mass height (depending on spring rate and travel), and use front max brake
torque of about 1600 N*m (each tire) and rear max at about 1000 N*m (about
60/40% f/r split)  This is with the new driveline model (locked diff, but it's
working with a simulated clutch now, yipee!) so the rear settings might be too
high if driveline inertia isn't included.  These brake torques increase
linearly from 0 to their respective max as brake input is increased.  

  Tires are usually 1.2 coefficient front and rear, although sometimes I drop
the front to 1.1 or so.  This lets the car brake hard at about 1.2g, locking
the fronts at the limit.  Have to still be a bit careful not to spin, but it's
manageble.  Anyway, it's some data you might have fun with :0P

  Of course, since you just released v0.39.2, maybe this is too late :-)

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://www.racesimcentral.net/

Because those suspension geometries transfer more of the weight
through the links bypassing the springs, the more anti- you
have, the less the sprung mass moves relative to the unsprung mass.
The springs compress less, but the weight (tire normal forces) is
still transferred, just in greater proportion through the suspension
links than through the springs.

- Matt

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/

Well you little... oh ok then. Let's see. ;-)

Yes, probably. But as you explained with the F12K numbers (which start
at 2.4 or something!) it might be the friction at 0 load, and you need
to take the load sensitivity into account.
I just moved up to Pacejka yesterday, and say these striking numbers:

b1=0, b2=1688 for a typical Ferrari-like car
b1=-7.6118, b2=1122.6 for a typical large front-wheel drive saloon
car.

Now when you look at the formula you see D=uP*Fz. And uP=b1*Fz+b2.
D, as you probably know, is somewhat like the maximum force that the
tire can generate (in the longitudinal direction). So, together with
the greek character, it seems that uP *is* the friction coefficient.
Strange that with the sport car, b1=0 so no loading sensitivy is
stated.
-7.6 looks way too high on the other hand, but Pacejka fools around
with units a lot, unfortunately making things less clear by doing that
(angles in degrees, Fz in kN).
So they set the friction coefficient at ~1.7 for the sport car still.
Weird.
BTW IIRC Ashley had a problem with 180N sideforce at 0 slip angle. It
doesn't seem I get this problem though. Will have to dig through my
archives to find it again. Perhaps a problem of mixing radians and
degrees.

Right, the Genta book states a typical value of 42 cm. I'm using that
now, including a weight of ~1500kg etc.

...

Ah, interesting, as I'm searching for nice numbers like this because
the car's still a bit loose (would you believe the Fx numbers from the
original curves and Pacejka were only off about 10% or so!).

I don't have the driveline inertia yet. Will have to, or use near-100%
front brake bias for now! ;-)

Doesn't seem like it. :)
It's nice, a have a very small but cute track which has a bridge. Also
got it to work yesterday so I can drive both under and on the bridge.
Cool! Suzuka here we come. ;-)

Ruud van Gaal, GPL Rank +53.25
Pencil art    : http://www.marketgraph.nl/gallery/
Car simulation: http://www.marketgraph.nl/gallery/racer/