rec.autos.simulators

by **Gerald Moo** » Wed, 23 Jan 2002 00:25:59

I was messing around at Talladega over the weekend, and decided to
remove the restrictor plates. One thing I noticed immediately is that
the tires started melting after only about 3 laps, and that for this
speed, were seriously over inflated. By decreasing pressures
signifigantly I got the temps to where they looked much better. The
overall temperature of the right side tires would still go red after
about 4 or 5 laps.

I went back in the track.ini and noticed a setting for tire heat. For
Talladega, this was 1.3. I looked at Atlanta and Michigan and it was
more like 0.90. After experimenting some at Tally, I settled on .75
(IIRC) where by driving carefully and coaxing the car through the
corners, the temps can be held just below the point where they start
getting too hot to provide optimum grip.

Another thing I noticed in the track.ini is tire wear. For Talladega,
it is set to 3, which indicates that tires wear 3x as fast here as at
a track set to 1. I didn't check the wear rates for other tracks.

All this got me to thinking about how N4 determines things like tire
heat and wear. Why are these factors different for different tracks?
I know Goodyear delivers a custom tire for each race, are these
variables supposed to reflect that?

In terms of "realism", what, if any, is the correlation between tire
temperatures and wear rate and available traction or grip? I don't
know much about tires, and zero about racing tires. Do stickier tires
wear out faster? What factors determine how hot a tire will get and
the temperatures it will endure before durability starts to become a
concern?

How do other games model things like heat and wear?

I have read that NR2002 has revamped this part of the physics engine.
Anyone with the demo looked further into this? What stuff have they
changed?

Gerald

by **John Pancoas** » Wed, 23 Jan 2002 01:45:47

Well, my .02 which isn't worth much :) Don't take the tire models to
seriously; they're not done to great. Tracks that are in actual racing
notorious for tire wear have relatively normal tire wear(Rockingham, i.e.,),
and others that are easy on tires have excessive tire wear, etc.

In general, a hotter tire will wear faster, as will a "grippier" tire.
Lots of things affect how a tire heats up; chassis setup, driving line,
track temp, air pressure, etc. WC cars get one compound per track(the same
one at some tracks), unlike open wheel series that can have several
compounds.

-John

by **Dave Henri** » Wed, 23 Jan 2002 03:05:47

I think you will find that many of these settings are just trial and
error. They have a target time and targets for tirewear, fuel consumption
etc. Once they know how many laps they need to run, they start adjusting
all the parameters til they have a fairly close approximation of those
factors. I'm sure a slide-rule math guy and get them pretty close but , and
this is just my own guess...
they just use trial and error.
Keep in mind that just because two tracks have asphalt for a surface, the
grip factors vary greatly. It's fairly common in race broadcasts to hear
the announcers talk about some tracks that eat up tires or some tracks that
are slicker than others. Even the time of year affects this...a spring race
vs a hot summer race. Or listen during the C***te 600 how a car running
good during the day turns to junk as the Sun goes down.
dave henrie

by **ymenar** » Wed, 23 Jan 2002 12:22:13

> All this got me to thinking about how N4 determines things like tire
> heat and wear. Why are these factors different for different tracks?
> I know Goodyear delivers a custom tire for each race, are these
> variables supposed to reflect that?

I'm not Papyrus, but I speculate it's a very good way as trial&error to find
an optimum realistic effect to the different tracks and the tyres Goodyear
bring. I know it's probably the "next big thing" in simracing to have
realistic tyre effects, and Papyrus is on the good road to someday achieve
that.

Ask anybody here, and they will all agree that tyre simulation is incredibly
difficult even for today's modern PC's.

If you check out the track.ini in NR2002, you will see the difference from
the same file in N4.

--
-- Fran?ois Mnard <ymenard>
-- http://www.ymenard.8m.com/
-- This announcement is brought to you by the Shimato Dominguez
Corporation - helping America into the New World...

by **jason moy** » Wed, 23 Jan 2002 16:07:01

I think the tire model is fine (as a whole), the problem is with
getting the heat/wear settings correct. The thing is, it's not just a
matter of factoring in the track surface, you have to simulate the
tyre compounds Goodyear uses at that track. Since Goodyear is
constantly changing tire compounds, I'd be surprised if a sim were
ever able to get the heat/wear variables 100% spot on realistic. This
year everyone killed their right fronts at New Hampshire, by next year
tire wear there may be minimal. It's no wonder some big name teams
(particularly Rousch) had problems last year with overextended tires
when there's really no consistency between the tires the teams are
given week-in and week-out.

By the same token, the values the original poster gave sound about
right. If Tona/Dega were being run without restrictor plates,
Goodyear would likely try to supply tires that were more up to the
speeds/cornering loads.

Jason

> Well, my .02 which isn't worth much :) Don't take the tire models to
> seriously; they're not done to great. Tracks that are in actual racing
> notorious for tire wear have relatively normal tire wear(Rockingham, i.e.,),
> and others that are easy on tires have excessive tire wear, etc.

> In general, a hotter tire will wear faster, as will a "grippier" tire.
> Lots of things affect how a tire heats up; chassis setup, driving line,
> track temp, air pressure, etc. WC cars get one compound per track(the same
> one at some tracks), unlike open wheel series that can have several
> compounds.

> -John

> > I was messing around at Talladega over the weekend, and decided to
> > remove the restrictor plates. One thing I noticed immediately is that
> > the tires started melting after only about 3 laps, and that for this
> > speed, were seriously over inflated. By decreasing pressures
> > signifigantly I got the temps to where they looked much better. The
> > overall temperature of the right side tires would still go red after
> > about 4 or 5 laps.

> > I went back in the track.ini and noticed a setting for tire heat. For
> > Talladega, this was 1.3. I looked at Atlanta and Michigan and it was
> > more like 0.90. After experimenting some at Tally, I settled on .75
> > (IIRC) where by driving carefully and coaxing the car through the
> > corners, the temps can be held just below the point where they start
> > getting too hot to provide optimum grip.

> > Another thing I noticed in the track.ini is tire wear. For Talladega,
> > it is set to 3, which indicates that tires wear 3x as fast here as at
> > a track set to 1. I didn't check the wear rates for other tracks.

> > All this got me to thinking about how N4 determines things like tire
> > heat and wear. Why are these factors different for different tracks?
> > I know Goodyear delivers a custom tire for each race, are these
> > variables supposed to reflect that?

> > In terms of "realism", what, if any, is the correlation between tire
> > temperatures and wear rate and available traction or grip? I don't
> > know much about tires, and zero about racing tires. Do stickier tires
> > wear out faster? What factors determine how hot a tire will get and
> > the temperatures it will endure before durability starts to become a
> > concern?

> > How do other games model things like heat and wear?

> > I have read that NR2002 has revamped this part of the physics engine.
> > Anyone with the demo looked further into this? What stuff have they
> > changed?

> > Gerald

by **Gerald Moo** » Wed, 23 Jan 2002 22:22:55

Is part of the problem that it is difficult to gather real world data
to validate the simulation? Or is it just that it eats lots of
processor cycles?

Gerald

> I'm not Papyrus, but I speculate it's a very good way as trial&error to find
> an optimum realistic effect to the different tracks and the tyres Goodyear
> bring. I know it's probably the "next big thing" in simracing to have
> realistic tyre effects, and Papyrus is on the good road to someday achieve
> that.

> Ask anybody here, and they will all agree that tyre simulation is incredibly
> difficult even for today's modern PC's.

by **Gerald Moo** » Wed, 23 Jan 2002 23:53:57

I played around some more. I raised the tire pressures back to where
I usually run them. This resulted in much cooler tires and not as
severe overinflation as when I first started mucking around. So I
raised the tire_heat setting up to 0.90 (same as Atlanta, IIRC) and
this again gets them to around borderline overheating.

Now I wonder, what kind of wear rate would be realistic for a tire
that could stand up to these speeds, and how would that affect
traction? I looked around for some baseline data, without luck.
Would a good goal be something like tires getting yellow (or even
almost/slightly red) at the end of a fuel run?

Gerald

> I think the tire model is fine (as a whole), the problem is with
> getting the heat/wear settings correct. The thing is, it's not just a
> matter of factoring in the track surface, you have to simulate the
> tyre compounds Goodyear uses at that track. Since Goodyear is
> constantly changing tire compounds, I'd be surprised if a sim were
> ever able to get the heat/wear variables 100% spot on realistic. This
> year everyone killed their right fronts at New Hampshire, by next year
> tire wear there may be minimal. It's no wonder some big name teams
> (particularly Rousch) had problems last year with overextended tires
> when there's really no consistency between the tires the teams are
> given week-in and week-out.

> By the same token, the values the original poster gave sound about
> right. If Tona/Dega were being run without restrictor plates,
> Goodyear would likely try to supply tires that were more up to the
> speeds/cornering loads.

> Jason

> > Well, my .02 which isn't worth much :) Don't take the tire models to
> > seriously; they're not done to great. Tracks that are in actual racing
> > notorious for tire wear have relatively normal tire wear(Rockingham, i.e.,),
> > and others that are easy on tires have excessive tire wear, etc.

> > In general, a hotter tire will wear faster, as will a "grippier" tire.
> > Lots of things affect how a tire heats up; chassis setup, driving line,
> > track temp, air pressure, etc. WC cars get one compound per track(the same
> > one at some tracks), unlike open wheel series that can have several
> > compounds.

> > -John

> > > I was messing around at Talladega over the weekend, and decided to
> > > remove the restrictor plates. One thing I noticed immediately is that
> > > the tires started melting after only about 3 laps, and that for this
> > > speed, were seriously over inflated. By decreasing pressures
> > > signifigantly I got the temps to where they looked much better. The
> > > overall temperature of the right side tires would still go red after
> > > about 4 or 5 laps.

> > > I went back in the track.ini and noticed a setting for tire heat. For
> > > Talladega, this was 1.3. I looked at Atlanta and Michigan and it was
> > > more like 0.90. After experimenting some at Tally, I settled on .75
> > > (IIRC) where by driving carefully and coaxing the car through the
> > > corners, the temps can be held just below the point where they start
> > > getting too hot to provide optimum grip.

> > > Another thing I noticed in the track.ini is tire wear. For Talladega,
> > > it is set to 3, which indicates that tires wear 3x as fast here as at
> > > a track set to 1. I didn't check the wear rates for other tracks.

> > > All this got me to thinking about how N4 determines things like tire
> > > heat and wear. Why are these factors different for different tracks?
> > > I know Goodyear delivers a custom tire for each race, are these
> > > variables supposed to reflect that?

> > > In terms of "realism", what, if any, is the correlation between tire
> > > temperatures and wear rate and available traction or grip? I don't
> > > know much about tires, and zero about racing tires. Do stickier tires
> > > wear out faster? What factors determine how hot a tire will get and
> > > the temperatures it will endure before durability starts to become a
> > > concern?

> > > How do other games model things like heat and wear?

> > > I have read that NR2002 has revamped this part of the physics engine.
> > > Anyone with the demo looked further into this? What stuff have they
> > > changed?

> > > Gerald

by **ymenar** » Thu, 24 Jan 2002 02:04:45

> Is part of the problem that it is difficult to gather real world data
> to validate the simulation? Or is it just that it eats lots of
> processor cycles?

I can't say much, but I speculate that tyre dynamics is presently a too
chaotic process to really be correctly simulated. Perhaps with Quantum
computers someday... ;)

--
-- Fran?ois Mnard <ymenard>
-- http://www.ymenard.8m.com/
-- This announcement is brought to you by the Shimato Dominguez
Corporation - helping America into the New World...

by **J. Todd Wass** » Fri, 01 Feb 2002 16:35:33

The biggest (by far) problem is getting real world data. This costs mega $$
to do on a stationary machine, although it's probably a little cheaper on
something like this:

http://www.ocp.tudelft.nl/tt/vehicle/testing/trailer.htm

The process is to (basically) start the tire rolling at a 0 slip ratio (free
rolling), then sweep it from a +20 to -20 degree (or whatever) slip angle and
save the force data. (In other words, with 0 slip ratio and 2.5 degrees of
slip angle, how much forward/rearward and sideways force is generated, and
what's the aligining torque?) This might first be tested with 200 lbs of force
(weight) on the wheel.

Then, you'd do the entire sweep again and again at different slip ratios (or
vice versa, not sure how it's really done). Then, you've got to do ALL of it
again at maybe 400 lbs or force, then again at 600 lbs, etc.. This takes a
long time ($) and can eat several sets of tires from what I've heard. The tire
temperature can't really be controlled yet from what I've read, and the tires
are continuosly wearing throughout the testing process, so you'd need to
probably "lock" a tire in at a certain slip ratio, load, and vertical force
(weight) to measure how the force changed as it was wearing down at each test
point you wanted.

Oh yes, then if you want all this data at different camber angles, multiply
the entire number of tests done so far by the number of camber angles you want
data for. The number of tests quickly multiplies many times for every new
thing you want data for. Want it at 10 different tire pressures? Multiply it
by 10 again.. Big, big $$.

Just for kicks, let's imagine getting data for the ultimate simulator:

If we wanted data for +/- 30 degrees of slip angle, at -.15 to .15 slip
ratio, taken in .02 slip ratio increments (just pulling these numbers out of
thin air). That's 15 test sweeps (say goodbye to the tire, probably). If we
wanted this done at 6 different tire loads, that's 90 test sweeps. If we
wanted all of this at camber angles from +/- 3 degrees, at every .5 degree,
we're now at 1080 tests.

Want 5 different tire pressures too? 5400 tests... And we haven't even begun
trying to compensate for tire temperature and wear yet..

I heard it can cost something like $10-20,000 just to run a basic test without
camber or tire pressure changes, so multiply that a few times to get the whole
thing. If a tire could stand 15 tests before wearing to the point where the
data is changing significantly, that'd be 360 sets of tires... Youch! lol
How much is a racing slick for Winston Cup? $3000? I dunno, but if it was,
that'd be a cool million $ just in tires, let alone testing time...

Once you DO have the data you want, it's not too difficult to include it in a
simulator, the CPU isn't really an issue anymore.

The good news is, there are methods that can do a good job of prediction
without making nearly all these tests. The MRA Radt non-dimensional approach
springs to mind, although I'm certainly no expert on it.

http://www.millikenresearch.com/mrandim.html

Todd Wasson
---
Performance Simulations
Drag Racing and Top Speed Prediction
Software
http://PerformanceSimulations.Com

My little car sim screenshots:
http://performancesimulations.com/scnshot4.htm

by **Gerald Moo** » Sat, 02 Feb 2002 02:14:38

Cool info!

GM

rec.autos.simulators

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