# Need Tire Help

#### Michael Brown

##### 500RPM
Hi there. I need help on tuning tires for sim racing. My questions are:

-What is the optimal tire temperature for touring cars and open wheel cars?
-What is the optimal tire pressure for touring cars and open wheel cars? In Psi and kPa, please.
-How does graining work?
-What should the difference in temperature be on the outer, middle, and inner part of the tire?

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#### Dennis Phelan

##### 8000RPM
I've been told that 90 degrees C is optimal but most tires won't get that warm. A balance between suspension and tire pressure will get you there. There is no single, magic pressure. The temp';s should be increasing from the outside to the inside, groping 5-10 degrees C as you find grip.

Everyone drives differently and even the fast guys can drive a range of car setups. It's all in the garage and on the track for you to find.

#### Kennett Ylitalo

##### 4000RPM
For Race07, the optimal tire temps are 90C in most cars (85C wet). Only thing that is slightly different from (maybe) reality and definitely different from all the setup guides: Try to get even temp on the middle and outside and about 7-8C higher in the inside part. You need XD to see them on track (you can download it from vitumo.de, follow the instructions on that page) What this means.. Slightly lower pressures than what should be. It's not much, just 5kPa lower will usually do the trick. If you got 90C inside and 85/85C middle/outside, you can't get any better traction than that.

#### Arne Dopudja

##### Leader of the infamous Chevy Gang.
I went by the rule of 84/87/90 that has been preached around here. Interesting, I'll try this.

#### Jempy

##### 1000RPM
I read somewhere that this tire temperatures are to be taken for each tire separately in the curve which make them the warmest ? ... in order to have a maximum difference of 5°C between inside and outside with a middle temperature between those 2 values.

True or false ?

#### Kennett Ylitalo

##### 4000RPM
Yes. But Race07 seems to have a slight favor of outside/middle to be the same. If you got 85/87/90 i'm pretty sure you can't feel any difference what so ever to 85/85/90. It's just a slight deviance from the norm. 90/90/102 is better than 90/95/102 and so on.. This is not a fact written in stone but leagues that have run a long time with same vehicles tend to come to same conclusion. It's not so much grip that is the issue but tire wear and grip combined with tire pressures, that combo seems to give couple of laps more in each stint.

It also depends on the track, if there are more straights you can use higher pressures even if it means middle temps run a bit higher than what is optimal. You get better top speed as rolling resistance is decreased. If the track has a lot of slow to medium speed corners, run pressures as low as possible to get all the grip available. The tire modelling does not use tire carcass simulation, thus lower pressures don't have the same effect on temperatures. Usually lower pressures means higher temperatures as the tire carcass deforms and bounces more. Race07 uses slip (how much the tire slips across the road surface) and load (how much weight is on the tire) to calculate temperature gain along with ambient temp and track temp of course. Wear is calculated only from slip and AFAIK, it doesn't have temperature degradation in the wear calculation.

It could be that even outside/middle temps mean the tire is more "flat" and so you have more contact patch but that is my own speculation. If tire deformation would be in the calculations, i'm sure the old real life rules would apply.

#### Arne Dopudja

##### Leader of the infamous Chevy Gang.
Yeah, this explains a lot. Ahhh, if only we get a decent touring car game with full tire simulation and so on.

I ran tests on Macau and I did go faster with your low pressure settings and I was faster sice it gripped better in slower corners. Thanks for the tip.

#### Jempy

##### 1000RPM
I don't wish to start a offtopic but shortly, is it the same conclusion for GTR2, Rfactor or AC ? if you know them as perfectly as Race07

#### Arne Dopudja

##### Leader of the infamous Chevy Gang.
Im gonna take a guess and say that it is the same for GTR2 and rFactor, but not for LFS, rF2 and AC. Those have better tire simulations.

#### Kennett Ylitalo

##### 4000RPM
It's the same in GT2 and rF. rF2 at least should have complete tire carcass model, i doubt LFS has. AC.. don't have a clue.

#### Chronus

##### 1000RPM
The tire modelling does not use tire carcass simulation, thus lower pressures don't have the same effect on temperatures. Usually lower pressures means higher temperatures as the tire carcass deforms and bounces more [...]

Actually, no. Lower pressures influence temperatures as should be expected.

Full carcass simulation (operative word here is FULL) and its effects can be found on advanced Pacejka models (physical, semi-empirical or empirical), though, truth be told, a model such as SWIFT also features these in the form of a rigid ring and flexible sidewalls and how the construct reacts to a set of varying conditions. Some simulations have claimed to possess "full carcass simulation" but...

However, ISI implemented a somewhat complex model where some variations were introduced into the basic concepts (as per an old interview of, IIRC, GJon, the model has its basis on MF96). As such, speed, pressure and stiffness effects are modeled.

Many different functions and parameters are interconnected.

Using explanations provided by ISI to my group (and some to the community years ago), and recalling Bristow's bible (we should give this man more credit than he has been given over the years), lets clarify the issue (and hopefully put the myths aside):

- the ratio of SpringBase to SpringkPa (tire functions exposed in the tbc/tyr files) affects the way in which the tire responds to changes in pressure.

- SpringBase and SpringkPa are used to "Define how springy the tire is and relates to elasticity and deformation of the tyre under load[...]it relates to tire heating"

- SpringBase, SpringkPa and tire pressure are interrelated in different equations, one of which modders use to calibrate proper pressure (optimum, multiplier and the default pressure in the hdv/hdc)

- springyness also has an effect on temperature calculations and heat generation calculations. A lower springyness tire will compress more and will get hotter.

- RollingResistance, which feeds into the heat generation equation(s), is also dependent on pressure (both default and dynamically varied)

- Heating, Transfer, AirTreadRate compound heat distribution/heat/pressure effects more.

- In particular, Heating (// Heat caused by (rolling, friction)):
Heating_param1 creates heat linearly with rolling speed and vertical tire deflection (which depends on pressure, of course, so less pressure builds up more heat).

This function permits management of heat distribution across the tire. For a given tyre, any increase in weight supported causes the outside edges of the tyre to heat in preference to the middle. This can be addressed in part by increasing the pressure in the tyre. Alternatively, the tyre will heat more evenly if this parameter is increased in line with the increase in weight supported.

A tire with lower pressure will deform/compress more (this also has a direct effect on the tire springyness), and as such will get hotter faster and longer for the same load when compared to a tire with a higher pressure.

There is an issue of the tire model relating rolling resistance and speed, but all things considered that is a minor thing to look at.

Now, all the above pertains to ISIMotor2 as used by rFactor and Game Stock Car (which, incidentally, was improved by Reiza themselves, according to Renato).

To my knowledge, though, SIMBIN did not change this; furthermore, Phantom Mark (M. Reynolds, at SIMBIN back then, the person in charge of AI and partly physics), admitted on NoGrip that they had made changes to the tire model and used different physics calibration models/strategies.

I don't wish to start a offtopic but shortly, is it the same conclusion for GTR2, Rfactor or AC ?

What I explained above is applicable to GTR2 and Race07. Do note, sir, that as I refer above, SIMBIN admitted to having made changes to the physics code, changes that have been considered "enhancements".

Im gonna take a guess and say that it is the same for GTR2 and rFactor, but not for LFS, rF2 and AC. Those have better tire simulations.

In order to make such a statement, people ought to 1) understand tire models, 2) know the tire models in use by all those sims and finally 3) actually know how ISIMotor2 works and what are its physics.

Almost all people I know or read about, know too little to make valid comparisons.

FYI:

AC:
- There was a debate going on at AC forums about the low speed grip issue (I read good posts from Mr Whippy and others in this regard). There were also problems with temperature management. Above all, several hardcore NetKar Pro simracers I/we know are a bit disappointed with the tire simulation in AC.

rF2
- as with C.A.R.S. and AC, it's an ongoing effort. It will improve over time. But just because it's new, it doesn't mean it's better. Had that same discussion with tire engineers and even Dave Kaemmer (iRacing) himself, saw no disagreement from anyone there. It's a bit naive to consider the so-called next-gen sims to be "more advanced this or that", in particular when one doesn't have actually factual knowledge of the "advancements". It's even more naive considering that these models are based on what tire engineers call "experimental explorations on tire mechanics". As always, it comes to my mind what real life experts call most of these tire physics developments: "models based on an incredible number of unproven assumptions".

LFS
- Scawen discussed at length and admitted to several problems/shortcomings with the tire simulations. Specifically:

1 - the change in circumference of a worn tyre is not modelled in LFS's current tyres (this from Scawen himself).

2- Tests done by LFSers show that tyre heating in LfS is "clearly broken, as the core temp is trailing the surface temps only by a couple degrees...". Not only that, "but at braking, tyre temp doesn't rise at all - it's only at cornering ".

3- LFS uses tyre wear variation only to know when will tyre become flat.

4- There is a so-called "perfect SPREAD of optimum temperature" (i.e., the inner, middle and outer edge and the inside of the tyre as well, all in perfect optimum temperature at the same time), which contradicts real racing. Scawen admitted that this "perfect spread" is a temporary solution for a certain problem they have.

5- It's a well known problem the issues LFS has relating tyre heating/cooling and tyre grip related to temp (in particular, 'overheating').

I'll add a my own (and of those I work(ed) with) oddity in LFS: the excessive bumpsteer of the GT cars under certain situations.

---

All in all, the idea of those "Those have better tire simulations" is a dubious, odd cliché. All tire models have their strengths and weaknesses. Higher complexity (as we learn in engineering or physics) does not mean higher accuracy or precision - often, it's the other way around.

Just my 2 cents.

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#### Kennett Ylitalo

##### 4000RPM
@Chronus : Thanks for the info. I have to admit, you can sound a bit annoying even when your are really really helpful but it's probably just me who feels that way, we got a little bit of history.. There's a ton of info that clears things up. I thank you from the bottom of my heart. You can't expect one has to know everything before they try to help others and i really don't want to end each sentence with "as far as i know." My "knowledge" is based on experiments and just driving, haven't studied in school or gotten any inside info.. Also, i don't have any knowledge from other sims. It is a bit strange that you know so much and aren't licensed RD member, do you drive sims at all?

In Race at least, one can't see any effects whether tire deformation has any effect or not, it's way too small to be noticed.. There are so much other things that make a lot more difference but it's good to know that it is there. The other parameters and their effects i knew or at least have guessed right.

What do you think of the temperatures on the outside/middle/inside being just a bit off from reality, ie outside/middle being closer to each other and inside part being higher, is there any truth in that? I've been always against it but have yielded as the tire just seems to last a bit longer that way and provides good or better grip than what it should be (if we don't think grip here, just to show what i mean, 85/85/95 is better than 85/90/95)

#### Arne Dopudja

##### Leader of the infamous Chevy Gang.
I have tested further andto have 1/4 increase in middle temp works best. As in 84-85-90 works just a little bit better in terms of grip. Though tire wear is very much down to the driving style.

You're right, complexer tire simulations don't mean better, but somehow the newer sims "feel" better.

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#### Chronus

##### 1000RPM
There's a ton of info that clears things up. I thank you from the bottom of my heart. You can't expect one has to know everything before they try to help others and i really don't want to end each sentence with "as far as i know." My "knowledge" is based on experiments and just driving, haven't studied in school or gotten any inside info..

I see.

No, I don't expect that. I started out modding/coding for simulations in 2001 and even today I am learning new aspects of sims I thought I knew reasonably enough, or even entirely new things.

There is a lot of value in revisiting articles or posts by the likes of Bristow, Kalma, Niels and more recently jtbo and juls in regards to rFactor. 95% of the things we talked about for rFactor are applicable to GTR2 and Race07. And a lot of things I myself tell people are based on that rather than "inside info".

Also, i don't have any knowledge from other sims. It is a bit strange that you know so much and aren't licensed RD member, do you drive sims at all?

I am somewhat a late comer. First "sim" I picked was Dave Kaemmer's Indy Car Racing, some 20 years ago. I then turned to the skies and space and picked every credible flight and space sim and it took a few years to get back to vehicle and race sims.

I have been "modding" and helping other modders and simracers for more than 5 years. It's been, mostly, pleasant. The community, though, has changed and not for the better, so...that's finito for me.

I don't have a license here, but have raced with iRacing and several other sims. LFS, netKar Pro, iRacing, rFactor, Race07, GTR2, GSC - all of them allow for private and public leagues. I have been fortunate to have entered leagues managed by motorsports professionals, who use rF, GSC and Race07/GTRE (nowadays it's mostly rF, rF2 and GSC, though).

It's funny how you equate not having a license here to probably not driving sims at all...Odd. There's a lot of activity outside RD, fortunately.

In Race at least, one can't see any effects whether tire deformation has any effect or not, it's way too small to be noticed.. There are so much other things that make a lot more difference but it's good to know that it is there. The other parameters and their effects i knew or at least have guessed right.

The following parameters are key to having (a) proper heat distribution, (b) visibly dynamic variations and (c) dramatic effects (on grip, wear, etc):

- SpringBase, SpringkPa
- HeatBasePeak
- RollingResistance
- Heating
- Transfer
- HeatDistrib

Specifically, tweaking the last 4 can have dramatic effects on temperature variation with friction, rolling, pressure, camber, stiffness.

By doing the above, you will definitely "see" the effects of being "below pressure" or "above pressure". Usually, though, modders (and even SIMBIN) have used values who prevent a fully dynamic temperature variation, maybe because it's not to everyone's liking.

What do you think of the temperatures on the outside/middle/inside being just a bit off from reality, ie outside/middle being closer to each other and inside part being higher, is there any truth in that? I've been always against it but have yielded as the tire just seems to last a bit longer that way and provides good or better grip than what it should be (if we don't think grip here, just to show what i mean, 85/85/95 is better than 85/90/95)

Yes, I felt uneasy about that as well.

First time I demonstrated Race07 to a pro team I used a set of cars from SIMBIN's GTRE (which they knew well and used extensively in their internal events). One of the complaints I got immediately was temperature. They argued real life temps were more spread and changed in seconds from a hot 95ºC to a cool 65ºC, and XD (the tool) showed none of that.

Again, as I said above, the figures given to factors/functions I refer above are the culprits. Variations due to slip must be fully dynamic [ HeatBasePeak = (0, 0) ], tire springyness must be close to RL figures and the same goes for damper. Also, RollingResistance must be lowered to RL figures (dramatically lower) . Then it's a matter of tweaking and tweaking the last 4 functions mentioned (with a wink to the grip variation clever trick, GripTempPress).

Picking your example figures (85/85/95), it shouldn't be like that. A "peak distribution" like 83/87/95 is closer to the data I have seen.

Does that have implications on grip? As you noted, yes, but the problem here, as always, is the full calibration model is wrong.

Most modders and devs alike are doing physics calibration models the wrong way. The key should not be to set a certain value for grip coeff and work from there. The key should be to establish an envelope of forces/energies and work from there.

If you do it properly, grip is retained across the board - obviously, with variations caused by pressure, temperature, slip, camber and load. Tires designed that way (with focus on forces and energies involved, rather than community-established values) are tires that feel organic and logical - no more "what the heck?!" moments in which you don't know what caused that spin or loss of traction.

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#### Chronus

##### 1000RPM
I have tested further andto have 1/4 increase in middle temp works best. As in 84-85-90 works just a little bit better in terms of grip. Though tire wear is very much down to the driving style.

Well, I for one can't say which setup tweaks work best, I haven't used generic/original physics for years.

I agree, whether with proper physics or "generic" physics, wear is very much dependent on one's driving style.

You're right, complexer tire simulations don't mean better, but somehow the newer sims "feel" better.

The (vast) majority of simracers try the "old" sims (with generic/original physics) and compare them with today's crop of "ultimate, next-gen sims". Not surprisingly, "old" sims are judged wrongly.

Even worst when it comes to comparing FFB from "old" sims and "new" sims. Somehow, people confuse FFB with physics and...again, "old" sims are judged wrongly.

"Old" sims such as rF, Race07 or more recently GSC, ought to be tried after extensive modding by less than a handful of people. Otherwise, it's just comparing apples and oranges.

Incidentally, differences between "old" sims and "new" sims come down to (after I fully mod the "oldies") to: "better graphics", "more FFB effects", "better sounds". Not a word on physics. For me and many others, this says a lot.

#### Kennett Ylitalo

##### 4000RPM
I agree fully and my tests does too. There is a definite lack of dynamic forces, they really are limited. I just recently did some testing for GP2 tire model and just by giving the physics engine chance to work freely proved to be the way to go, tire temps changed much much faster, everything started to make sense. That is interesting, heatbaspeak(0,0), i have to try that.

I know why they use those values are found in most of mods and SimBin default content: it's "idiotproofing"... If you use "real" values and give responsibility to user, they usually the complain too much, it gets "too hard" and some tracks just wont work.. My approach is totally opposite, give the user total control and the responsibility of their actions: one just can't drive like they want but have to take care of their tires. It also means that tools like XD is totally mandatory... I got GP2 2013 and recently acquired permission for SuperKart 250 conversion. I would really love to hear your opinion on them, when it's time to start testing them: i know for fact that the feedback is brutally honest, that is sometimes hard to get (and if you got time/enough motivation/interest) So far i'm really happy with the results.

#### Chronus

##### 1000RPM
I agree fully and my tests does too. There is a definite lack of dynamic forces, they really are limited. I just recently did some testing for GP2 tire model and just by giving the physics engine chance to work freely proved to be the way to go, tire temps changed much much faster, everything started to make sense. That is interesting, heatbaspeak(0,0), i have to try that.

If you go for the fully dynamic HeatBasePeak (all zeros), you will have to contend with more aggressive temperature changes and peaks. Race07's original physics calibration wasn't prepared for this, neither did GTRE's. You will have to tweak all other params (including pressure settings), but it is definitely worth it. A lot of work, but it'll do great things for your simulated vehicles.

I know why they use those values are found in most of mods and SimBin default content: it's "idiotproofing"... If you use "real" values and give responsibility to user, they usually the complain too much, it gets "too hard" and some tracks just wont work.. My approach is totally opposite, give the user total control and the responsibility of their actions: one just can't drive like they want but have to take care of their tires. It also means that tools like XD is totally mandatory...

I did the physics for several leagues. The vast majority of complaints I had to contend with came from casual gamers and simracers with ZERO real life experience of racing. What's even more odd, what was acceptable or "spot on" for real life pro drivers, was considered "too difficult" or "arcadey" - go figure.

I agree with you. You, me and even Aris think along similar lines, make the models as realistic as possible and enforce real life behavior by letting people know where the limits are (for both the physics and racing rules).

The reason SIMBIN, SRW, Blimey/SMS and even ISI physically calibrate the cars as they do is, they say and swear by, to reach a wide audience, the nuts and bolts simracer and the casual gamer (those that right now are all jumping high on account of AC).

I think that is the wrong strategy and told this to several studio heads - obviously, they disagree.

I got GP2 2013 and recently acquired permission for SuperKart 250 conversion. I would really love to hear your opinion on them, when it's time to start testing them: i know for fact that the feedback is brutally honest, that is sometimes hard to get (and if you got time/enough motivation/interest) So far i'm really happy with the results.

Hey, I'll gladly try your mods and conversions. Though I spend most of my time with modding GSC2012, I still consider Race07 one of the best racing sims out there. If my feedback can be of value to you, I'll give it - whatever we can do to keep rF/Race07/GTR2 alive lets do it.

#### Kennett Ylitalo

##### 4000RPM
With all of our differences in areas that do not involve motor racing or simulation of it, we do think a LOT a like. That is not actually surprise to me, just worth noting Taking those "safety features" off makes it a lot more difficult. but i think it's worth it.In FPS world we got this thing called "promod"

Just by putting more "realistic" tire simulation, i noticed those weird "always go soft" suspension setups don't work anymore and they are starting to creep up closer to values i've been able to get my hands on. And i've never seen tire temperatures change so fast, third of a lap can make a huge difference (still just +-5C but a lot different what i've seen so far, 15C in one lap just by driving differenly) and one has to really start to take care of them. Race07 tires take a tremendous beating until they react at all.

When i got time, i'll get the tire model finished to next round of beta (the first one was basically alpha for tire model, with individual slip curves for all four compounds.. i still got a hell of a lot to do with aero, ... but at least aero is just pure physics and math with very well defined rules, there is just no way i can get any data from Pirelli.. lol... and it's all interlocked, one thing changes another then third one changes the first but so far i'm happy that i'm at least pretty close). Once i get to the next stage, you will be first i'll PM ,most likely before beta group (they are just too kind, hard to get negative feedback....and that's the only thing that counts..). But i think i need study the parameters all over a more. First tests were done with very simple values ( 1.0 where ever i could, nothing of that 1.234234 crap), just entered them in there for fun and the car just worked like one would expect.. Also what i learned from inertia, a lot of ingame models and even more so with modded content, they use high mass and low inertia (or vice versa), just putting those without any safety what so ever, just pure physics.. First test showed behavior and lap times that made sense from the first laps onwards. but i would surely need a well educated second opinion.

I believe RBR used rFactor Pro up to 2009.. That should tell anyone what kind of physics engine we are tinkering with.. SimBin locked a lot of values and made their own FFB response, other that that, it should be pretty vanilla.

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#### Chronus

##### 1000RPM
As a side note, I am often asked why am I sticking with rF, GSC or Race07 (or with NKP or LFS) with "all that's going on with the next-gen sims".

That's a legitimate question, isn't it, all the hype and marketing machine-gunning must account for something and most simracers are facing it more and more. Why stick to "old" sims?

Hmmm...

Without going into details of how work is done inside a development studio, I'll say this again:

- even dev teams work within standard boundaries due to limitations imposed by knowledge, data, tools and time constraints;

- dev studios FREQUENTLY do not have the FULL info about cars (manufacturers often send simple brochures instead of relevant data) and they have even less data about tires. [Don't fall into the hype/marketing stunt of Greenaway that they (Turn10) will be revolutionizing the science of tires...]

So, much as I like the breathtakingly beautiful graphics of Project CARS, I inevitably focus on what really matters simulation wise: physics, mechanics, pure racing. Knowing the pitfals/shortcomings of the current development models, strategies and organization, knowing what I wrote above, it's totally impossible for me to accept the sophistication and novelty hype surrounding pCARS and AC.

Plus, after years of studying different physics models, I will comfortably settle for rF, GSC or Race07 for the next 2 to 3 years. The eye-candy or a ton of new, "never before experienced" FFB effects are pretty much irrelevant for me (fortunately, for others too). "Very sorry, hype-machine..."

Just by putting more "realistic" tire simulation, i noticed those weird "always go soft" suspension setups don't work anymore and they are starting to creep up closer to values i've been able to get my hands on. And i've never seen tire temperatures change so fast, [...].

Indeed.

The physics calibration model I advocate involves a full rework of cars. FULL.

Most modders aren't prepared for that kind of work and the implications of it all, and mostly due to:
- by doing so, we enter totally uncharted territory. Unless you really, really know what you are doing and where you're heading, you'll be in for months of headaches and frustration.
- it's really, really a ton of work in all areas: chassis, aeros, tires. And that PER CAR.
- realistic simulations being increasingly more difficult the closer you are to the limits of car and tires. It takes time, persistence and intelligence (in experimenting with the setups best suited to you) to get the most out a simulated vehicle, to become faster. Not all simracers and their leagues are up for this challenge, imo.

When i got time, i'll get the tire model finished to next round of beta (the first one was basically alpha for tire model, with individual slip curves for all four compounds.. i still got a hell of a lot to do with aero, ... [...]

Eheh.

Well, my strategy (and the entire process) is actually pretty simple.

I start out with "Car basic data":
- mass, estimated CoG, weight distribution (front to back). A multi-block or integral-defined shape approach will give me inertias, aero coefficients (body), etc.
- fuel
- dimensions (length, width, height, track width)

Wheels, tires and brake disks:
- mass, dimensions. From this, inertias get calculated. In the absence of full data, one of the preset data models will yield proper results.

Wings and splitters:
- given width, chord, height, shape and placement, I model an envelope of minimum to max downforce achievable (i.e., from 1º to typical values/settings, anywhere from 10º to 17º, depending on the shape of the airfoil)

Diffusers:
- it's a little bit different and mostly based on data given to me by teams.

Tires:
- there's a lot of info out there about compounds, tests, etc. Some of it is in raw format, some of it comes from graphs which are a bit difficult to read from, some of it comes from books...and fortunately, some of it gets released by the likes of Michelin, Avon, Hoosier and Bridgestone. Getting to know someone within the industry is key to understanding how to translate all the info commonly available, all the data shared by teams, into practical models.

Telemetry:
- While some modders have been fortunate to work with RL teams (in spite of technical problems here and there) and indeed there's a lot of data from data acquisition systems we can use (within the confines of NDA's). But occasionally, some files or data sheets surface here and there. I saw telemetry data from pre-season tests of a GT team competing on an european championship a couple of years ago, and that was posted on their website. A rear wing manufacturer (sorry, can't recall the name) posted some wind tunnel data on their latest products. The new Viper SRT aerodynamics devices team posted a study detailing some of their findings (and partly the process) on the new set of splitter and rear wing.

From there, it's simple:
- What are the maximum speeds on straight?
- What are the expected max cornering forces at 60 kph, at 100 kph, at 160 kph, at 200 kph?
- What's the expected braking distance (depending on speed)?
- What type of tire compounds to model? What tire widths?

Like in real life, tire compound and width will allow us to calculate the grip coeffs, load bearing capacity and expected slip angle envelope (for maximizing forces). From this, we get, depending on load, what forces the tire will develop.

That's the stepping stone of simulating a vehicle.

Then, if you know the engine output, you know how fast it can go. If you know how fast it can go, you can calculate how much downforce you will get from splitter+rear wing+body+diffuser at whatever the speed. If you know the downforce, you know the load PER TYRE, therefore you know the cornering forces developed for the car (depending on speed).

Some of the things we have to contend with afterwards are:
- weight distribution + aerodynamics CoP (we can work with splitter CoP + Body CoP + Diffuser CoP + Rear wing CoP, in order to understand the overall aerodynamics distribution and its effects on load distribution)
- springs: natural frequencies, etc
- dampers
- ARB's
- suspensions: geometry, component mass, component inertia, dimensions, etc

I do a somewhat generic treatment of engines (power output, shape of curves, heat generation, cooling, engine braking) and gear ratios.

What I never do:
- tweak tires to match the aeros or tweak both to match the desired "feel" (there's a very well known mod group, with ties to several motorsports teams and personalities, that does this...). There is no feel involved. [A somewhat known modder - he did, at some point, the physics of a well known GT league - sent me furious emails on how he could never mod by equations, that it destroyed all "feel"...]
- use impossibly high grip coeffs (example: F1 tires level of grip - official estimates range from 2 to 2.2 - applied to GT and proto racing)
- use unrealistic levels of downforce. 95% of modders do this to compensate for the lack of proper force generation
- use street cars slip angle envelopes on GT and proto cars. 95% of modders do this because their cars don't stick to the road properly (whatever the physics engine) and when they snap, they snap with zero possibilities of recovery.
- use low inertias. 98% of modders go by a simple "copy and paste" rule (if it works for that car, it should work for this), and as such errors related to inertias simply spread all over the modded content (and developer made content as well). Modders and devs use low inertias due to lack of information, carelessness or because it makes cars react faster to driver input. Problem is, cars are 950 to 1430 kg entities, they offer resistance to change of state. Without this "resistance", cars seem to be made of cardboard. The whole physical behavior goes down the drain due to this seemingly unimportant factor.

For me, by following the above, I stick to the rules of the real world. The physics engine, though not perfect, reacts very well to proper input. The cherryh on top of the cake is that more than a few simracers (especially the RL pros) enjoy and demand cars done this way.

Once i get to the next stage, you will be first i'll PM ,most likely before beta group (they are just too kind, hard to get negative feedback....and that's the only thing that counts..). But i think i need study the parameters all over a more. First tests were done with very simple values ( 1.0 where ever i could, nothing of that 1.234234 crap), just entered them in there for fun and the car just worked like one would expect.. Also what i learned from inertia, a lot of ingame models and even more so with modded content, they use high mass and low inertia (or vice versa), just putting those without any safety what so ever, just pure physics.. First test showed behavior and lap times that made sense from the first laps onwards. but i would surely need a well educated second opinion.

Sounds like a really good plan. You can PM me then.

I believe RBR used rFactor Pro up to 2009.. That should tell anyone what kind of physics engine we are tinkering with.. SimBin locked a lot of values and made their own FFB response, other that that, it should be pretty vanilla.

Indeed.

The thing that some people are so bent on ignoring (and making sure others ignore it too) is that, while not an engineering tool, rF/ISIMotor2 can be used as a high level tool for driver preparation. With proper setups (a 6 DOF motion platform, 3 screen split, full telemetry) drivers can begin their preparation for upcoming seasons without the need of expensive track testing or costly simulation-hours.

If it's good and credible/realistic enough for the pros, why not for the rest of us?

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