Suspension 101, for street cars

[jtbo]

When starting modding and even if you have some experience in modding, here is perhaps something useful I stumbled upon, some reference values and information to help to understand why everything is as it is:
http://www.sae.org/students/presenta...pension101.ppt

Anything relatively modern seem to be quite low, for racing purposes 2-2.5Hz is good aim, anything around 3Hz or more of wheel rate must have downforce or load added, I believe, to get Hz you can use this tool, just remember that motion ratio and difference in wheel rate and spring rate, adjust numbers you input accordingly.

Edit 25.1.2012 6:50AM: Attached latest version of my calculator spreadsheet, all formulas are now verified and working, added also new stuff to damper calculation as I finally came accross to info I remembered seeing years ago, but only until now managed to find anything about it.
That was Rebound to Bump damping ratio, so I made three values for that to make it easier to pick appropriate bump damping for calculated rebound damping, also added some explanation of that to orange area.
That calculation should now help a bit more to get dampers in range, but as always drive and test car well, try to find measured data from dampers, but from my experience that is really hard, during 5 years I have came accross only Miata damper results and some generic data, but nothing really useful apart from that.
Damper calculations should be verified with real world data, might try Miata stuff some day and see if I can get them converted to rF units and find all the data from those cars to make comparision of real data and what my calculator gives, but for me calculator produced values seem to work quite well, feedback however is always welcome.

According to this site:

http://www.smithees-racetech.com.au/performancefactors.html
Frequency for road car is 1.33 - 1.67Hz (CPM to HZ = CPM / 60) and from presentation you can see how modern cars have 1.1-1.3Hz at front, of course modern cars are hardly a 1000kg weighting either. For 1000kg race car they suggest max of 2.17Hz.

For example Corvette C6 HDV has front spring at 22500 and in comments there is mention of 1.3Hz rate and that is a sports car.

ISI ZR has frequency of 2.11Hz at front, that is in HDV, so it is full grown race car with only looks of steet car at base A tune, any upgrades will make frequezy just higher, getting weight reduced will make frequency higher so that is partly why it has that feel of go-kart instead of a car.

Many mods have been using values close of 100 000 or even higher resulting suspension that is close to iron bars instead of springs as modders have not had information how things are in reality.

Often modding is guesswork when there is no data available and result is more or less questimate, but with this information it can be closer questimate. Of course better if one has the data.

Using real world spring values is making sense only when motion ratio is known, if not known, then set wheel rates and get frequency to proper range, even better if one can get it measured from real car. AdjustSuspRates= is setting to adjust depending from if one likes to set wheel rates or spring rates + motion ratio.

To get those US spring units into rFactor units you can use this, multiply by 1000 is required though to get right unit to HDV as I believe in HDV unit is N/m and to convert mm to m (meter) you need to multiply by 1000:
http://www.convertunits.com/from/pound/inch/to/N/mm

That should give some insight of how to make car act like a car instead of go-kart, inertia and cg height (link to get idea what is range where those should be) plays part in that too as well as dampers (Need to be enough soft to allow easy body movement and after braking typically one bounce, but remember firm ride is often made with dampers, not just by stiffening springs, one need to adjust according to vehicle), so it is always sum of many, but by reading and understanding presentation chance of success is multiplied by many times

Same applies to rF2 also, there might be of course some different parameters to play with, but frequency is still same stuff and same goes to any sim in that matter.

Hopefully this is some help for someone in a future.

edit: Here are few links that contain real world skidpad results of various kind of cars. Please, do note that peak G forces what you see at Motec when driving around the track can be higher, skidpad results are often constant G force when driving at steady maximum possible speed while still keeping same line on 200ft or 400ft circle, you need such test track which preferrably has real world road parameters, means that track friction should not be too optimistic. I have been told that 1.0 would be too high for such, but then again I don't know much about track making.

Anyway here are the results that might give some insight of what to except from street cars, there are also some sport cars and I think one can be considered as race car:
http://xenon.stanford.edu/~kpfleger/auto/handling.html

http://www.angelfire.com/tn2/america...rs/TheList.htm

Here is bit insight to old vs new american muscle for those interested, 1969 Z28 getting 0.8G:
http://www.thirdgen.org/ford-vs-chev...view-march1992

Anyway those should give at least some direction to what kind of numbers can be excepted, tires of course are big part, but suspension and Center of gravity (CG height, CG rear) are big part in there as are springs and dampers too.

When building a car, if nothing else, one should try to get into correct range of performance and cornering as that is what gives players immersion of driving that actual car and not just car that looks like that actual car, when you get skidpad results, acceleration, braking, top speed, inertias, cg height and suspension frequency close, it is almost certain win already in my books at least.



Edit Springs:
Okay, let's put up some information here about springs.

Let's say you have pulled of coil spring out from your car and try to figure out how on earth I get this into rFactor.

No worries, Mid-West Spring and stamping to the rescue!
http://www.mwspring.com/software.html

I think that is the most accurate spring calculator, I have tried lot of those online calculators, but those don't seem to quite cut it, often I end up way too high rates, but this tool seem to get it much closer.
Good thing is that it is very light and fast.

Measure spring, input units, in case you live in metric world, you need to convert measured units to imperial ones first, active coils is usually total coils -2.

Choose compression spring and if your spring ends are cut so that top of spring is flat, then use ground button, if ends are not cut then the button on left of ground button, after than push calculate.

At lower section next to Buckling ratio is button with letter M push that and you see Newtons at Rate box, rememember to multiply that by 1000 to get right units for HDV.

You might be lucky and find spring data from internet too and you can use this tool to calculate them to proper units.

Just remember that often there is motion ratio of something else than 1 and that must be put into springmult= but mostly all McPherson setups are 1. Alternative is to work with wheel rates, then this tool is not so useful.
Motion ratio or wheel rate are both very difficult to come by however, easier to find such vehicle from junkyard perhaps and measure there or if doing your own car it can be measured from the car. Google measuring motion ratio will give lot of help with this one.

[JJManeschijn]

Very interesting, educational and helpful, thanks!

It is very true that the springs of most of the mods in both rF and GTR2 are way too hard (and inertia values too low), the main reason most probably being as you state "...as modders have not had information how things are in reality".

[jtbo]

Originally Posted by JJManeschijn

Very interesting, educational and helpful, thanks!

It is very true that the springs of most of the mods in both rF and GTR2 are way too hard (and inertia values too low), the main reason most probably being as you state "...as modders have not had information how things are in reality".

Just remember with GTR (maybe same with GTR2 also?) that motion ratio and also parameter springmult= in hdv, which can be used to lower or increase wheel rate, from my memory, which is often at fault, there was 0.5 or such value in GTR?

There is then still motion ratio, in rfactor .pm file pushrod location affects that, of course it all depends again how setting AdjustSuspRates= has effect to that, so judging wheel rate is not necessarily quite as straight forward than just looking what is value in springrate setting in HDV.

For simplicity one can set AdjustSuspRates=0 and pushrods at spindle to get nice and easy suspension setup without need of thinking motion ratios and such, I really recommend taking adjusting in steps, one can get same handling without worrying too much about that motion ratio than with doing all the hard work, so at start better to go simple road with wheel frequencies.

However it is true that often frequencies are too high and inertias too low, to what extent it is not so simple to point out, sometimes it may look that springs are hugely stiff, but it might only look so, motion ratio can cause wheel rate to be quite ok, but then comes dampers which may be overly stiff for that particular setup.

That is also very important to understand when looking some mod and attempting to learn from it or even at adjusting some mod, which also is great way to learn how to build own mod one day.

[Vette4Life]

I've tried GTR2 lately and the cars have A LOT too much grip, the rear end will never step out just a bit and it feels like there is no suspensions whatsoever...

Was it suppose to be the best sim ever ?

[jtbo]

Originally Posted by Vette4Life

I've tried GTR2 lately and the cars have A LOT too much grip, the rear end will never step out just a bit and it feels like there is no suspensions whatsoever...

Was it suppose to be the best sim ever ?

Sounds similar to other Simbin products actually, kind of their trademark, but then again haven't driven GTR car. However GTL too has similar tendencies, maybe not quite so bad, but to some extent and when you spin out wheels locked car going around and come to stop car is kind of static without body movement, while in reality there is quite a lot of body movement in such situation.

Inertia, cg-height, springs and dampers are most that really affects to that feel, also tires in GTR, however that is their view how they like it to be and in a way there is lot immersion factors done really well, with some finetuning it is possible to make even GTL cars so good that I find it difficult to get all that in rFactor.

Actually all these suspension things apply well to GTR and GTL too, add 20-30% more inertia to those cars and this kind of suspension adjustments and it is whole different world.

[tiptop]

Thanks for the thread, great one.

[kingjames100]

Interesting.

Completely over my head, but interesting indeed.

[rafa281]

Very good!! Thank you, I'm downloading Power Point Viewer so I can see the first thing about suspensions you refer to.

[rafa281]

Originally Posted by jtbo

Sounds similar to other Simbin products actually, kind of their trademark, but then again haven't driven GTR car. However GTL too has similar tendencies, maybe not quite so bad, but to some extent and when you spin out wheels locked car going around and come to stop car is kind of static without body movement, while in reality there is quite a lot of body movement in such situation.

Inertia, cg-height, springs and dampers are most that really affects to that feel, also tires in GTR, however that is their view how they like it to be and in a way there is lot immersion factors done really well, with some finetuning it is possible to make even GTL cars so good that I find it difficult to get all that in rFactor.

Actually all these suspension things apply well to GTR and GTL too, add 20-30% more inertia to those cars and this kind of suspension adjustments and it is whole different world.

Hi there, very interesting article! By the way, how do you edit the physics files in GTR2 and Race 07? And what are the names of those files?

Thx in advance!!

[Chronus]

Originally Posted by jtbo

Sounds similar to other Simbin products actually, kind of their trademark, but then again haven't driven GTR car.

The idea (wrong) that GTR2 cars have too much grip has been proven to be a fallacy for a number of years. Lack of knowledge keeps perpetuating it, unfortunately.

At least, some, like you, try to learn isiMotor2 physics and understand the various sims based on it, which is positive.

jtbo, by now you know there many strategies to modding isiMotor2 based racing sims. By now you probably know how to calculate the real level of grip each car has and also how sensitive these cars are to suspension movement and load transfer - everything is due to how the devs set up the physics calibration of these cars.

However GTL too has similar tendencies, maybe not quite so bad, but to some extent and when you spin out wheels locked car going around and come to stop car is kind of static without body movement, while in reality there is quite a lot of body movement in such situation.

Inertia, cg-height, springs and dampers are most that really affects to that feel, also tires in GTR, however that is their view how they like it to be and in a way there is lot immersion factors done really well, with some finetuning it is possible to make even GTL cars so good that I find it difficult to get all that in rFactor.

Inertias were reduced, I was told, to increase responsiveness of cars to human control.

Often, the values used by most modders and devs for inertias are 40 to 50% off. [Worse, in regards to brake discs the deviation is quite shocking.]

Obviously, when you input the proper figures for inertias (car, axles, wheels, brake discs), changes are dramatic and immediately noticeable.

Regarding rFactor...I recall interesting posts by David Wright, davehenrie and Aris explaining the main difference between rFactor's isiMotor2 and the customized version of the game engine used in GTL and GTR2. Easy to see that ISI did a lot of corrections and improvements on isiMotor2, which makes rFactor effectively "newer" than either GTL or GTR2. In that sense, rFactor is more "moddable" or "adjustable" than either GTL or GTR2.

[NOTE: Anyone really interested in exploring the possibilities of rFactor should read and re-read many times over the threads and work done by Bristow (can't say this enough: we should give this man a LOT of credit for his persistence, work and genius), Niels, Chris Hoyle, Kalma and the rest of the RSC guys.]

As you imply, though, the "immersion factors" play an important role in GTL and GTR2.

Actually all these suspension things apply well to GTR and GTL too, add 20-30% more inertia to those cars and this kind of suspension adjustments and it is whole different world.

Not as simple as that.

You have to take into account several factors:
- inertias
- centre of gravity / weight distribution
- spring and damper ratios
- suspension geometry
- rollbars
- the use of bump-stops

Inertias alone imply an awful amount of work - unless you're satisfied with ballpark figures which may be 10 to 20% off. As I said above, recalculating inertias involve chassis inertia, axle and wheel inertias (hdv and pm files) and brake disc inertias. Once this is tackled, though, the feel and physics of cars is dramatically altered.

[LeSunTzu]

Originally Posted by Vette4Life

I've tried GTR2 lately and the cars have A LOT too much grip, the rear end will never step out just a bit and it feels like there is no suspensions whatsoever...

Was it suppose to be the best sim ever ?

A very simple modification to tyre files can change that dramatically.

[jtbo]

Originally Posted by Chronus

Inertias alone imply an awful amount of work - unless you're satisfied with ballpark figures which may be 10 to 20% off. As I said above, recalculating inertias involve chassis inertia, axle and wheel inertias (hdv and pm files) and brake disc inertias. Once this is tackled, though, the feel and physics of cars is dramatically altered.

Always pleasure to read your comments

For inertias, there is small tool that tries to ease off work a bit, it is called Car Inertia, but as with any tool, care must be taken to make it work properly, it is very easy to end up with 50% off.

This suspension stuff I have known actually from before rFactor came about (real world stuff), but to translate it and understand how gmotor2 needs to be fed is thing where probably always is stuff to learn.

Even Bristow has made great job with opening up all parameters, I think there could be more to be done to make it understandable for even beginner modder, wording, examples, maybe some tools, maybe someday I can get them ready

Anyway that inertia from HDV alone, if it is 20-30% too low car becomes completely different vehicle, something comparable of what purpose built race car is compared to street car without any modifications and indeed easily they can be far more off, that is why there is link to sae paper where are measured inertias, so that one can estimate what might be correct when making car.

What I have played with rFactor, from early 2006, one thing I have found out, suspension geometry can be way off, for example independent instead of de-dion rear axle, it has effect, but I can feel it lot less when driving than if springs, dampers or inertias are off by that said 20%. Front geometry is of course then felt at steering wheel, but even there changes seem to have quite small effect compared to these settings that we talk at this thread.

Also then there is those tires, now if one gets CG height bit wrong, lets say that one eyeballs CG-height to be 0.2 above reference frame, when reality is more likely to be double of that, it has bigger effect than suspension geometry has to feel of the car, it has also big effect to that how many G's car pulls at skidpad, but now tires, if one puts perfectly good tires to car that has such flaw, it is easy to make conclusion that those tires are at fault, then often dryLatLong gets adjusted, which has no real reason to be adjusted at that point and this easily starts a snowball effect where at the end modder ends up with car that sometimes performs right, it feels wrong and sometimes performs wrong. I believe that such is called masking the cause with english language, sayings and terms are sometimes difficult to translate.

Understanding this danger is important and to avoid that knowing how much different areas in parameters effect and to what kind of car behaviour can help even beginning modder to find right path easier.

Some are probably wondering how to calculate inertia of brake disc. I shamelessly copy stuff from net http://www.engineeringtoolbox.com/mo...que-d_913.html
I = inertia
I = 1/2 m r^2

m = mass of cylinder (lbm, kg)
r = distance between axis and outside cylinder (ft, m)

So for simplicity lets think brake disc being solid simple disc without much of shape, weighting 10kg and having radius of 0.1 meters. Values are unrealistic and discs are not quite simple solid cylinders, but for most it should be enough to get even that close, values are unrealistic so that it would be easier to begin with, when putting values to car, real disc should be of course measured and weighted.

Calculate like this:
1/2 (or just write 0.5) x 10 x 0.1^2 = 0.05

Note that for those not knowing, ^ symbol is used for exponent and as we have ^2 it means same as 0.1 x 0.1, just put this here so that if someone is as old as me and has forgotten almost anything taught at school from math, it is easier to pick up than running all over the internet finding meaning of silly roof symbol.

We can then try with some real values. E46 BMW 316i front brake, data from Brembo website:
Weight 6.2kg
Diameter 286mm

So first we must make Diameter to be Radius and also we need to convert it to meters. 1 meter is 1000mm and Radius is Diameter / 2, so:
286 / 2 / 1000 = 0.143 that means radius is 0.143 meters.

Inertia can be calculated then by this way:
1/2 x 6.2 x 0.143^2 = 0.0633919

That will of course be bit off, there are holes in disc, it is not same thickness all the way from center to edge and so on, so one need to estimate how much effect that will have to result, edge has most effect to inertia, anything close to center have quite small effect to inertia, then one must estimate how much effect there is going to be, that is simplest way that I know of, those who know better ways can speak up

In HDV one then finds out this kind of line:
BrakeDiscInertia=0.600 // inertia per meter of thickness

Note that it is inertia per meter of thickness, I haven't found any info or anyone who would been able to tell me how to get calculated inertia converted to rFactor's units, but I have been telling myself it must be Newtons and so I have multiplied result with 9.81.

That would give me 0.621874539, which is close to what I see for example in ZR's HDV, but indeed so far I have not been able to verify or deny of this.

I would take 10% off from the result to make up as brake disc is not perfect solid dics, but for that also I have not heard or seen anything from anyone at anywhere, so be my guest and correct my assumptions if they are hugely wrong.

I think that kind of underlines what is challenge most of the time, to know which units rFactor needs and how to get your calculated stuff correctly converted, some might know well many numbers from car, but when units are like two different languages and that is not tutorialized or even slightly opened, it causes many modders to use something that just works.

Anyway I hope we can find answer to this and I can write down it so that as simple as I can understand it

edit: Here is link for diagram of brakedisk I used in example, Brembo's website is quite nice for such information really:
http://bremboaftermarket.com/En/Car_...e-a3aff0f9a0c9

[Chronus]

Originally Posted by jtbo

Always pleasure to read your comments


For inertias, there is small tool that tries to ease off work a bit, it is called Car Inertia, but as with any tool, care must be taken to make it work properly, it is very easy to end up with 50% off.

Thank you, jtbo.

As for the inertia tool...

It is a start, but it still is off by a few %.

This suspension stuff I have known actually from before rFactor came about (real world stuff), but to translate it and understand how gmotor2 needs to be fed is thing where probably always is stuff to learn.

Imo, your comments on the suspensions of cars from isiMotor2-based sims (from GTR, rFactor to GTR Evo and Shift2) are interesting.

I think that suspension design became a issue with many mods due to lack of proper data; also, a significant portion of modders prefer to rely on suspension design already done by others.

isiMotor2 allows for some leeway in suspension design; however, designing suspensions takes a tremendous amount of time and requires data which is also difficult to come by. Which is a pity, after all, as you say, inadequate suspension design can either mask or seemingly create tire problems.

I agree, there's still a lot of work to be done - I'm sure that will propagate as well to rFactor 2.

Even Bristow has made great job with opening up all parameters, I think there could be more to be done to make it understandable for even beginner modder, wording, examples, maybe some tools, maybe someday I can get them ready

When I think back to the RSC years...

I spent most of my time working (12 to 14 hour work days were common then) and whatever little time I had left for simracing I invested in privately modding GTR2 and rFactor. The threads originated by Bristow, the info-rich posts by himself, Niels, Kalma, PeterV, Speed12 (ISI), Carham, kangaloosh, LBodnar...Without these people, modding on the isiMotor2 platform would be very hard, so a huge number of simracers and modders for ISI/Blimey/SIMBIN/SMS simulations owe them a debt of gratitude.

I think the threads are simple enough in their wording. The thing is, chassis physics, tire physics and aerodynamics are not simple subjects (some people regard them as black-magic, go figure ), in order to address them, to discuss them in depth one has to deal with equations and technical terms the average modder has no knowledge of.

On top of that...

Take a look at some of the comments posted here and elsewhere. A significant number of people ignore what a simulation is; a significant number of people have little or no knowledge on tire-chassis physics and aerodynamics; most simply burp something they read somewhere which probably was written by someone who also happened to have read something written by...You get the picture. In the end, modding is best left to those that know what they're doing, those that pulled all the stops to understand what simracing physics and isiMotor2 are all about.

Anyway that inertia from HDV alone, if it is 20-30% too low car becomes completely different vehicle, something comparable of what purpose built race car is compared to street car without any modifications and indeed easily they can be far more off, that is why there is link to sae paper where are measured inertias, so that one can estimate what might be correct when making car.

I developed my own tools for that and have always checked their output against SAE papers showing US-government measured vehicular inertias (lots of cars, from the late 70s to the late 90s).

Years ago, I was stunned when I compared the inertias used by modders and devs (for a number of known simulations, not all isiMotor2 based) and real life inertias (I had figures collected on a number of cars). Differences were BIG. Then, I came across SAE papers and US-govt papers - differences became horrific, close to being 50 to 60% off.

No wonder simracing cars usually feel as if made of paper.

Now, put back the missing chassis inertias and cars become alive:
- they do not accelerate instantly
- they do not stop instantly
- roll becomes noticeable, even with stiff suspension (whereas with the usual (wrong) inertias, there is little or no movement of the chassis to the sides even with mid-settings); obviously, the more stiff suspensions are (even with proper inertias) the less roll there'll be

Also then there is those tires, now if one gets CG height bit wrong, lets say that one eyeballs CG-height to be 0.2 above reference frame, when reality is more likely to be double of that, it has bigger effect than suspension geometry has to feel of the car, it has also big effect to that how many G's car pulls at skidpad, but now tires, if one puts perfectly good tires to car that has such flaw, it is easy to make conclusion that those tires are at fault, then often dryLatLong gets adjusted, which has no real reason to be adjusted at that point and this easily starts a snowball effect[...]

CG height is important to chassis physics, I agree, but its impact on tire feel is tied to roll centres (front and back). It is true that roll couple lengths affect weight transfers, which in turn affect both the car responsiveness and mechanical grip.

This is yet another area of simracing physics, and isiMotor2 physics in particular, that is hard to get right (take carFactory out of the equation and you only have Suspension Editor to visualize the results of your suspension design). And yes, it can have deep effects on how tires feel - not tire physics per se, but how they feel and react.

Probably best to keep as close to hard data (real life) as possible. Problem is, information on cg heights (part of the roll couple problem) is not easy to find. Sometimes, we're left with best estimates because we have info for some cars but not for others.

Some are probably wondering how to calculate inertia of brake disc. I shamelessly copy stuff from net http://www.engineeringtoolbox.com/mo...que-d_913.html
I = inertia
I = 1/2 m r^2

You have to take into consideration the density of the materials, the mass of the disks or its size (diameter and thickness), if they are ventilated or not, drilled or cross drilled or not...

The equation used by devs is this (with variations):

I(z-Axis)=1/2*PI*Thickness*Density*[(OuterRadius^4)-(InnerRadius^4)]

or

I(z-Axis)=0.5*PI*Thickness*Density*[(OuterRadius^4)-(InnerRadius^4)]

If you use 33 mm thick steel disks 340 mm in diameter, you end up with Iz brake disk inertias around 8.70 (// inertia per meter of thickness).

Compare that value with 0.001 used by most modders and devs.

Now, add to that suspension file inertias (wheels and spindles) and hdv (hdc) files wheel inertias (spinInertia).

There's a lot of things to change in order to bring isiMotor2 cars to their full potential.

[mrpowcz]

Interesting and pretty shocking - about inertias.. I also felt many cars feel too twitchy and light as a feather and wondered why when they had correct mass and other things you can see in garage/showroom.. but it's not really mass that makes a car feel heavy, it's inertia.
I also remember when a former F1 driver (think it was Hamilton) drove a 1930s grand prix car and said the car feels heavy as a battle tank. I wondered how could the car feel heavy when it weighs 700kilo.. well it had so huge inertia it actually behaves like a modern 1400 kilo GT car, except the light weight allows hard acceleration.

Just had a look at a 67' F1 mod - not the f*1*c one, its an unallowed conversion too but different mod and for the purpose of this thread: weight 500 kilos, Inertia=(330.1, 413.0, 82.9)
Especially the last number is a joke, should be at least 2 times more - and the car does handle like an angry bird, you have no time for corrections.

[jtbo]

Originally Posted by Chronus

---clip----

You have to take into consideration the density of the materials, the mass of the disks or its size (diameter and thickness), if they are ventilated or not, drilled or cross drilled or not...

The equation used by devs is this (with variations):

I(z-Axis)=1/2*PI*Thickness*Density*[(OuterRadius^4)-(InnerRadius^4)]

or

I(z-Axis)=0.5*PI*Thickness*Density*[(OuterRadius^4)-(InnerRadius^4)]

If you use 33 mm thick steel disks 340 mm in diameter, you end up with Iz brake disk inertias around 8.70 (// inertia per meter of thickness).

Compare that value with 0.001 used by most modders and devs.

Now, add to that suspension file inertias (wheels and spindles) and hdv (hdc) files wheel inertias (spinInertia).

There's a lot of things to change in order to bring isiMotor2 cars to their full potential.

I quote only a bit to help readability.

That paper feeling car is my most dislike in simulator cars, it kinds of puts away any interest to drive immediately, actually it is reason why I am a modder of ISI sims.

I would say that mostly there is no hope for average modder to get mod perfectly right, but I imagine if all these are explained enough simple way, like what is effect to end result, we could see cars that are at least feeling to be closer than what there is today, trying to say that 5% error is a lot better than 50% error, if 50% of mods released would get to that 5% it would be already huge improvement, much bigger than what there has been in last 10 years.

I still remember when Simbin was born, they were modding group (I think it was Racesims revolution?) at the time and after working long time for mod project that was supposed to be successor of ETCC mod for F1C they chose to release it as a new game, really long time so can't remember all the details. Their handwork was easy to recognize back then and still cars have that same character. I made quite bit of inertia changes to that F1C ETCC mod to get car feel more car, 9 years or something ago, we are still someway at same steps

We might not share opinion about who should make mods, but let's not allow that to bother, it is just opinions, which have never built any car

Once here I was testing two versions of car, two veh files, one was with independent rear suspension, other was de-dion axle, then I forgot which one I was driving (that happens a lot nowdays) after some testing I was absolutely sure that it was independent suspension version, did not go outside from car to check, but so it did happen that it really was one with de-dion axle, there was no way telling difference when driving.

Front is then easier, you feel all the changes at wheel.

Thank you from those formulas, first time I see them. What unit they use for density? Steel's density is 7850 kg/m^3 but one can have it in grams, Newtons etc.

Those inertias in .pm file are not per meter of thickness, so they should differ a bit from brake disc inertia, I think.

If finding data for some race car is difficult, I suggest trying old van or truck (big rig, heavy hauler, how americans can tell if it is pickup truck or that huge one?) , most of the stuff must be estimated as data from those is such that nobody desires it

[jtbo]

Originally Posted by mrpowcz

Interesting and pretty shocking - about inertias.. I also felt many cars feel too twitchy and light as a feather and wondered why when they had correct mass and other things you can see in garage/showroom.. but it's not really mass that makes a car feel heavy, it's inertia.
I also remember when a former F1 driver (think it was Hamilton) drove a 1930s grand prix car and said the car feels heavy as a battle tank. I wondered how could the car feel heavy when it weighs 700kilo.. well it had so huge inertia it actually behaves like a modern 1400 kilo GT car, except the light weight allows hard acceleration.

Just had a look at a 67' F1 mod - not the f*1*c one, its an unallowed conversion too but different mod and for the purpose of this thread: weight 500 kilos, Inertia=(330.1, 413.0, 82.9)
Especially the last number is a joke, should be at least 2 times more - and the car does handle like an angry bird, you have no time for corrections.

What makes inertia bit difficult to get is probably that it indeed is not the mass alone that affects inertia, but it is where that mass resides in relation to pivot point, which in case of car is centre of gravity, so one can have 100kg and 200kg objects having same inertia to some direction.

I don't think that any car I have made has perfectly right figure, some may be close, but there is always margin of error as I really can't afford to spend days or months in single parameter, which it would require for me to get it perfectly right, but I think having it somewhere in correct area is worth of goal to reach alone.

Wheel inertias in .pm file are btw quite important too as well as masses as those affect quite a bit to car's behaviour when cornering and braking/accelerating, there unsprung masses and slowness of mass (inertia) have some effect and then of course bumps, but to find good bumps on tracks one might need to even change track few times as sometimes off track areas are quite smooth too. Of course understandable as it is lot of extra work, but uneven surface with good bumps is really needed to have good experience.

For me too high inertia is easier to tolerate than too low, that then might cause too high inertia values when I make something, but do and learn from mistake if such happens, that is how we improve.

[mrpowcz]

I know, and it definitely seems most modders put way lower, not higher values for inertia.

[Chronus]

Originally Posted by mrpowcz

Interesting and pretty shocking - about inertias.. I also felt many cars feel too twitchy and light as a feather and wondered why when they had correct mass and other things you can see in garage/showroom.. but it's not really mass that makes a car feel heavy, it's inertia.

In order to achieve a realistic behaviour in regards to load transfer, chassis roll, acceleration times and braking distances, proper mass and inertia figures must be entered. When we do so, everything comes together pretty nicely - even considering the quirks of pMotor2.

Obviously, when we tackle inertias, other things must be taken care of as well, otherwise you'll have cars behaving as tanks. Best example of how to deal with this properly is NetKar Pro's Vintage GT - considerable lift, smallish tires (by today's standards of GT racing) and as a result we have a twitchy but slow moving car (in regards to manoeuvres), a car that feels heavy ("as a tank").

Same problem affects current simulations as well - with the exception of GSC (chassis inertias are quite close to RL).

Originally Posted by jtbo

We might not share opinion about who should make mods, but let's not allow that to bother, it is just opinions, which have never built any car

Yes, well, there clearly is (for me) a line separating two camps:
- skins/graphics/sound mods
- physics mods

Simracing needs both, no doubt.

But this need should be fulfilled with quality not quantity - this is not happening in regards to Physics, though.

Hundreds of mods made for rF/GTR2/Race07. Different cars, sometimes different eras - yet, we look into suspension, tire and chassis files and we stumble upon the same values used and reused many times over.

Hopefully, this will change with rF2.

No, a modder doesn't need to have a degree in Physics, Mathematics or Automotive Engineering - but a serious modder has to know his/her way around the territory of physics. If a modder can't tell the difference between the physics of a cart and a GT car, then he/she should not be allowed to do physics modding. PERIOD. Bad physics modding is bad for modding in general, and very bad for the sim in question (one of the preferred grenades used by iRac**** fanatics, actually, the "low quality of rFactor mods" which for them magically translates to rFactor having "bad physics").

Originally Posted by jtbo

Thank you from those formulas, first time I see them. What unit they use for density? Steel's density is 7850 kg/m^3 but one can have it in grams, Newtons etc.

Those inertias in .pm file are not per meter of thickness, so they should differ a bit from brake disc inertia, I think.

Preferred unit of measurement is kg/m^3. The density of steel varies between 7760 and 8040/8050. Simulations I have worked with use 7800 as the most plausible value for known applications (aircraft, car chassis and axles, brake discs, etc).

Regarding the PM file: it's been like this for years, for me and many others, it's kgm^2. If you give wheels (in PM) the specs cars use (wheel size, wheel mass), the result is exactly given in terms of kgm^2 (bigger for pitch, the same for roll and yaw).

[Stigasawus]

Interesting to follow, though, just being a (dumb?) driver I dont get the detail as much as the overall picture.
Made me wonder, without intending to knock any of the guys doing all the work just for me to have some fun...what about track surfaces. Obviously different surface material is part of the equation but I dont think I've driven on any "billiard tables" in the real world.
Some irregularities are in just the wrong spot, though some can be damn useful too.
Sort of stretches this thread but I feel its related, sorry to complicate things...just interested in the response re rF tracks.
The cornering/ braking ability can be affected greatly by even a small tyre pressure change BUT how accurately do you rate the tracks that all your work on the dynamics of the car is going to be applied to. I reckon a lot of sim track builders are working without the possibility of full information or even the chance of finding info...which you guys have at least a chance to find (eg Brembo site)
They do a great job considering! Some tracks or former versions are only memories now. So how does this half of the equation fit with your quest for realism?

[mrpowcz]

That's quite easy to answer imo, sure the track surface is very important too but whether is real or not doesn't really affect how we should pursue realism of the car itself. Let's say car is 70% of realism and track remaining 30: if we have 100% real car and 50% track, than that's 85% overall, if we have 50 real car and 50 track its only 50% overall.

It's definitely true surface is very simplified in rf1, first of all nearly all tracks have exact same level of grip. Then comes bumps which usually aren't at exact places, instead you set periodic microbumps with the same severity on whole track in terrain file. Then there are no groove, marbles, not even surface temperature is in rf1. When it's freezing tyre warming is a different story than when it's 40 degrees celsius. It's not fault of track modders, in rf1 this really isn't possible to do without changing code of game itself.

All of this is brought to different level in rf2, for me that's even better news than the new tyre model.

[Chronus]

Good posts, guys, good points made.

Stigasawus, mrpowcz hit it square on.

I'll look into iRacing as an example. There are known problems with tire physics (aerodynamics is yet another cloudy area) they're trying to solve, yet its tracks are considered super accurate. The question many ask is, what good are these tracks if the underlying car physics are not on par?

A totally different angle or spin on the issue, I gather. The answer to those asking the iRacing question seems to be: cars may be off the mark, tracks are spot on, so iRacing itself can be used for learning tracks, not for experimenting with the cars or even experiencing them.

isiMotor2 tracks can be very good in the areas of graphics and accuracy. For instance, VLM's tracks, for rFactor or SIMBIN titles, are very impressive works - attention to detail is stunning (Mid-Ohio, Lemans and Sebring are superb).

Can these tracks reflect all irregularities? I doubt it, not even iRacing's are that perfect (though they say they are).

But it is possible to represent all high wavelength bumps or undulations, and possibly the smaller, higher frequency ones as well. Not all of them, but probably more than enough to give the feel of accuracy to the track.

Is it possible to model different levels of grip and bumps?

Yes. Per material used, several variables can be used for many purposes:
- Dry
- Wet
- Resistance
- BumpAmp
- BumpWavelen
- Spring
- Damper
- CollFrict

So, you have different sections (from the perspective of track designer) to which you apply different materials, which in turn can be defined through those variables.

Not all track designers put this level of detail in their work, however.

Still, car physics per se can and must be viewed independently from the tracks. Bottom line is, whatever the track (regardless of accuracy) cars must behave as they should.

[jtbo]

I don't know much from track making, but I have made few tracks for my testing purposes and I know how real world tracks near me are.

Real world track surface is like if you took sheet of paper from printer, crumple it to ball and then straighten it, scale that to around 100 times or so, where rfactor tracks are often like uncrumpled smooth paper, well that is just a comparison to tell the idea of difference.

In reality there are humps and dips, can be 5 x 10 meters, sometimes only at half of track and even having center point at edge or outside of track, so that there is also camber change in that dip.

There are micro and macro dips and so on.

Car's suspension must work all the time and that makes more comfy cars bit uncomfortable to drive at fast pace.

It really does not affect much to grip of the car, only when car starts to bounce around in corners it causes car being unsettled or change direction at straight so that more grip would be required, hence why stiffer suspension is usually required.

I think that with that reason you can get away with softer suspension in rF than what would be possible in reality.

This is one of my forever WIP projects I think, this is raw GPS data from one road I know of, scenery just thrown there to be temporary distraction, some practising of making real size ditches too, it is not much at this stage, but at least it has bump or two, so I can use it to test suspension limits a bit, you can take your favourite car there and test bit how it will handle roughness. That is mainly tracks use, to test suspension and bit of handling, but as of current it is not quite realistic test, however I consider it being better than smooth track.
This is still too smooth at places and perhaps a 'bit' too rough at places, just to make you aware and not except wonders, after all I'm not that great track builder, it is not quite my area, but to make something unpopular in rF you have to make everything by yourself so it is learning process at beginning steps for me, physics are still learning process even I have been pursuing it for close to 10 years, learning bit there, bit here, always trying to open up and share when I get something right so someone could take two steps at once instead of struggling with one step
http://jtbo.pp.fi/tiedostot/rfactor/Partaharju3b.zip

This is real version of track, so you can see there is quite bit of difference still, even real one has snow covering most of details it is still easy to spot differences, can't remember FOV of my Canon MVX200i, but to get same look one would need to use similar fov too as it affects quite a bit how hills and corners will look like, well that would be needed only for comparison purposes, speed limits were of course followed.
http://www.youtube.com/watch?v=KPPccxQKPQE

Snow is funny surface to drive one, depending from tires and such, it pulls car to side or other randomly and sudden, also depth and what kind of snow that is affects to that pull, with that car had to always 'fight' to snow, never have seen a sim that does snow even closely right, don't think there even is worth noting sims that have tried, but same goes for gravel too.

If car is made from real values or even estimates that land relatively close (by using Hz of natural frequency it is easier to land into zone when doing estimates route), then it is good on smooth and also good on rough tracks, in ideal world no estimates would be needed, but it is often unavoidable if one has car he likes to recreate, to find 70's average passenger car in brand new condition and take it apart for testing components in car laboratory, I doubt that anyone here has such resources, but only way to get original damper rates etc. Many kinds of dynamometers would be needed, brake, damper, engine, would be really great to have such resources though

But I think that when we can establish good common value range that alone steers unwary mod maker away from 50% or more off values.

For those willing to learn, here is document that partly is dealing with suspensions from roll over perspective, which gives some good insight also.
http://www.scribd.com/doc/26693404/3...hassis-systems

I think that there is maximum weight what can be used in rFactor, have been playing now with from 15 000lbs up to 60 000lbs and despite setting tires to handle all that weight they start to misbehave, car sliding down to hill when parked, wheels stop rotating and slide especially at slow speed, only way is to have tire half empty to overcome issues and that creates other issues, feels like something in gmotor2 engine would go out of bounds. Anyway that underlines one important factor that we don't know, which are limits of engine's parameters that still are in safe range.
Most likely cars in 600-2000kg range are ones that would work best as around there are ISI cars too.

I have in garage one car that has rear leaf spring rate around of 15 000 (rF hdv units), car weights 1075kg and has almost 50:50 weight distribution, I can see how wheels can move a lot dpwnwards, compared when I set spring four times that value, then I can't get wheel to move as much down no matter how high I set rebound travel. It would make sense to have limit in range when wheel moves up, but down too?

So that must be some limitation or some other feature where from I have not seen much of information, building few examples of such things that one must also take account to will be of course useful when trying to understand workings of engine, so at some point I hope to be able to make those, but I need to understand first much more and now there is rF2 also, where this suspension stuff is still probably useful, tires have nothing common to rF1, which might be a good thing

[Stigasawus]

Thanks guys. Glad no-one thought I was critisizing.I dont have the smarts to take advantage of all of this but it helps with understanding what I'm involved in. (Sometimes I'm just not game to attempt adjustments suggested in case I stuff everything & have no one around to physically dig me out of the hole...my son who used to do the rescues is now 100's of K's away & got a bit impatient with fossils like me anyway).

I often wonder about the comparisons between say rF & similar alternatives but rF was what I discovered first & didnt know the rest existed really till I came to No-grip after googling all over the net. Cant see how iRacing or anyone can get perfection but I enjoy cars or tracks or forget about them & move on. I like the idea of as much realism as possible but if say a track seems pretty close, thats great as long as the components even down to ripple strips etc are close enough....great.

I "went for a drive" specifically to compare real & sim in 2008, just to see how much I'd have to compromise & after about 15 hot laps I went home & did it again....I was pretty impressed...not exact but happily close enough & glad my real laps didnt cost me any more than my sim laps (I've been lucky to drive OP's a lot in my time)

So I'll keep on trying to learn about the software side...leave it to you guys...& keep working on my cockpit. Keep up the good work & I'll keep enjoying the fruits of your labours AS LONG AS YOU KEEP PUTTING THEM ON FORUMS. After all I havent found a book on Sim Racing for Dummies..yet!

[jtbo]

Originally Posted by Stigasawus

So I'll keep on trying to learn about the software side...leave it to you guys...& keep working on my cockpit. Keep up the good work & I'll keep enjoying the fruits of your labours AS LONG AS YOU KEEP PUTTING THEM ON FORUMS. After all I havent found a book on Sim Racing for Dummies..yet!

I don't know about Sim Racing for Dummies, but I try very hard to pull off rFactor modding for Dummies, as I'm one of those Dummies and forget everything if it is not put up somewhere, so I make these treads so I can return and learn same thing again which I forgot, when I'm enough confident of stuff I add it to my book, which I plan to put online when it is in form of some usage to others too.

RSC was nice centralized place for all the information, but when it went down it has become really difficult to find all bits of info, so that is one of the reasons such 'database' is needed.

At least I don't know anything like this for ISI sims, but that is what I would like to have:
http://www.modwiki.net/wiki/Main_Page

Also to make realworld data to rF units, haven't seen any tutorials about such, or database of formulas etc.

It just might take some time to pull something like that off, especially when there is very much that I don't know.

Well, this is perhaps bit of OT already.

Anyway, I have been testing rF2 now from when beta came available and Belgium track is something we have not had in rF1, it is not smooth at all and finally first time I noticed Asphalt being higher than ground around it, this is very small thing, you really don't see it unless you go to ground level, but this has big effect when you step out from black stuff in real world and one of things why I have been attempting to make my own tracks as it adds whole new aspect to driving and car testing too.

That is making suspension setup much more important, very low and stiff is spinfrenzy on such tracks.

There is bit of such on rF1 track Montventox, but it still is not quite as bumpy, but I think one of best tracks for car building in rF1, also it loads real fast, Targa Florio is good one too, but it loads quite slowly, shorter ones seem to be rather billiard table like, somehow roughness is with long tracks.

Lapping is perhaps bit difficult, but I tend to run back and forth of some section that has nice combination of everything, I get data for both ways that way too

Oh that suspension setup and natural frequency (Hz) is not useful only at car building, you can actually compare setups of two different cars with that, also it is useful to set springs by frequency and adjust ride height after that so that you are not constantly bottoming out, higher ride height always wins one that bottoms out at every corner as driver can max out potential better during the race, with car that bottoms out driver have to be over cautious constantly and this keeps driver from using full potential of the car.

Working with setups is not much different from tuning suspension of car when making mod, but there are just more areas that modder need to play with.

[jtbo]

Sorry for double posting.

I did attach my Kodi ZR to this post, I'm not claiming it to be most realistic ever, I don't know really what size that is, but I did some eyeballing

Anyway I did tune it to be sporty street car, you should be able to get quite sideways with this too, with LVL1 tires and type Z engine and exhaust, keep rest type A level.

Mainly some suspension tuning and inertia stuff done, I have my own tires for it too, but so far I prefer default tires.

I use FOV 35 and steering lock at 20, realfeel -5500 and mix 90% from my memory, G25 set to 900 degrees, that is if you like to try it way I drive.

Dampers are quite soft, especially at rear, springs and ride height set what I thought might be possible for such sporty vehicle.

I like driving this a lot, with not so great brakes and bit loose suspension you need to work it a bit, think ahead of corner and balance weight to right tire to make good corner entry, then adjust balance of car with throttle trough the corner. Setup options are very limited by purpose. There is still lot to be done for this car, but it is already nice sample of how car can change with quite small changes.

Would be interesting to hear what others like from such car

[WildBill]

Thanks jtbo----I`ve been working on the Sportscars50 mod and after I thought I was done with the physics and the mod was released---I came across this thread---increasing inertia values made a very satisfying difference to the way the cars handled---it took away some of the snappy breakaways and got the suspension and feel of the cars to be closer to real life.

It really didn`t take a lot of adjustment to notice a difference---think it turned out to be around 10% or less----now the cars feel a little more planted and you can feel through the FFB that the suspension is working better.

Anyway--will be included in the next mod update----so----thanks

DRAGON

[jtbo]

Originally Posted by WildBill

Thanks jtbo----I`ve been working on the Sportscars50 mod and after I thought I was done with the physics and the mod was released---I came across this thread---increasing inertia values made a very satisfying difference to the way the cars handled---it took away some of the snappy breakaways and got the suspension and feel of the cars to be closer to real life.

It really didn`t take a lot of adjustment to notice a difference---think it turned out to be around 10% or less----now the cars feel a little more planted and you can feel through the FFB that the suspension is working better.

Anyway--will be included in the next mod update----so----thanks

DRAGON

Glad to hear this is useful thread

Here is my race ZR with tires to go with it. Tires are almost same as original ZR LVL1 tires, but I did change pneumatic trail, heating, optimum pressure, rolling resistance and springbase + springkpa (these based from what Cubits did say about those values).

Also drylatlong is changed to be closer to what their compund name says "street".

At least I think those are ZR base tires, can't remember if I have changed them years ago, but doubt that.

Mostly there is bit less grip around corners and much better feel with realfeel, you can compare default tires by changing in hdv line that says ZR_tires_lvl1b to ZR_tires_lvl1, there is not so much of difference, most difference in handling comes from HDV changes, mainly suspension and inertias.

Car is set up so that it is safe for new drivers but also provides some thrills for experienced driver, it is perfectly possible go sideways in corners and control slide with throttle, but do that a lot and you cook your tires.

That is perhaps best example of how I see what is realistic behaviour. Remember to upgrade only engine to Z type, everything else A type.

Oh and this one has sequential box, using stick preferred, gear up forward, I made it to be like mechanical sequential box which I have experience from, sadly still allows downshift without lifting throttle, real thing does not.
Diff is something like viscous coupling.

[Chronus]

jtbo,

a few considerations, if I may.

There were reports (some people may still recall that Avon Tires and Michelin published a few data sheets on this around 2009/2010) about the expected tire coefficient of friction of street tires relative to several types of surfaces. On top of those, the Hunter Engineering Company, Goodyear and (iirc) BFgoodrich published a few findings (duly patented...) on several compounds. Globally, these reports/studies/papers paint an interesting and somewhat clear picture in regards to some of these tire characteristics.

In light of that, I would advise against this:

- DryLatLong=(1.105, 1.354)
Too low Lat coeff. From SAE papers to other sources, Mu, from the lateral forces point of view, and from a "base load", is around 1.25 to 1.35 (some sources report 1.72 as the upper boundary friction coeff between tire rubber compounds and asphalt/tarmac). On top of that, the difference between Lat and Long is less pronounced than implied by the figures you use

- SpringBase=49.05
This is TOO low. If you look at the specs or inferred data on tires from the mid-60s to the 90s, the spring rates at zero inflation are much, much higher than that.

Specifically...

From a SAE conducted study, the absolute lowest figure I found for this was 300 lbs/in, but more commonly 789 lbs per inch, or 3509.6468 N per inch. That's PER INCH alone.

Also, SpeedEffects_param1 can have a stabilizing effect. The figures usually used are too low - add to that SpeedEffects_param2 and how it affects peak slip angle at the nominal loads provided.

Telemetry (tire loads and lateral forces columns/channels) can certainly help in understanding this better.

[jtbo]

Originally Posted by Chronus

jtbo,

a few considerations, if I may.

There were reports (some people may still recall that Avon Tires and Michelin published a few data sheets on this around 2009/2010) about the expected tire coefficient of friction of street tires relative to several types of surfaces. On top of those, the Hunter Engineering Company, Goodyear and (iirc) BFgoodrich published a few findings (duly patented...) on several compounds. Globally, these reports/studies/papers paint an interesting and somewhat clear picture in regards to some of these tire characteristics.

In light of that, I would advise against this:

- DryLatLong=(1.105, 1.354)
Too low Lat coeff. From SAE papers to other sources, Mu, from the lateral forces point of view, and from a "base load", is around 1.25 to 1.35 (some sources report 1.72 as the upper boundary friction coeff between tire rubber compounds and asphalt/tarmac). On top of that, the difference between Lat and Long is less pronounced than implied by the figures you use

- SpringBase=49.05
This is TOO low. If you look at the specs or inferred data on tires from the mid-60s to the 90s, the spring rates at zero inflation are much, much higher than that.

Specifically...

From a SAE conducted study, the absolute lowest figure I found for this was 300 lbs/in, but more commonly 789 lbs per inch, or 3509.6468 N per inch. That's PER INCH alone.

Also, SpeedEffects_param1 can have a stabilizing effect. The figures usually used are too low - add to that SpeedEffects_param2 and how it affects peak slip angle at the nominal loads provided.

Telemetry (tire loads and lateral forces columns/channels) can certainly help in understanding this better.

Thank you Chronus

Coeffs are from LFS, just wanted to do small test

SpringBase is adjusted so to test point Cubits did make, about empty tire and how empty tire carries a load, it really does not. Of course higher springBase would lessen effect that pressure has to springyness of tire, it can be that base is so high because it is wanted that pressure has less effect.
Total spring of tire is from my understanding springbase + springkpa * pressure.

I think problem there is that I was thinking a load that should make wheel touch the ground, which is of course different from spring rate, but maybe it should be possible to come up with spring rate when I measure load required to overcome the spring, just haven't found formula that does that yet.

Spring design software says from one of my real car springs that they are 27.784N/mm rated and for those force to fully compress them is 5 064.27N, corner weight of that one is around 260kg from my memory, so is tire's spring rate any way comparable to coil springs? It is not much more than 10kg that is required to push empty tire to flat, that is less than 100N, what is mixup here? Is that springbase only springrate of that tread rubber, not meaning how much sidewalls act as supporting springy things?


Mostly I wanted to have just pneumatic trail to be suggested value, but then I got into tweaking mayhem and tested that Cubits idea and LFS coeffs as I stumbled to them (apart from drylatlong everything should be so that behaviour of tire is same as ZR originals), but even if we let everything as in original ISI tires, but change pneumatic trail to my set value, car still is really nicely handling, just pulls very high amount of G-forces, 1.25 I think it was, but that is how those LVL1 ZR tires are, they are no street tires despite the compound name.


Totally unrelated to this vehicle, I wonder about that 1.25 minimum, getting 0.7G with such would require quite horribly messed up geometry, I think at least, but there are quite bit of older vehicles that are 0.7-0.75 range. Even with drylat 1.1 getting less than 0.8 I think is quite challenging, at least with accurate suspension setup, this tirestuff is something where I have lot of black holes so to speak, even have learned effect of most parameters, I find that what param. should be used get too good tires constantly.
But I guess that is completely another topic those tires.

I ask these questions to understand better why, not to question what you say, just wanted to make that clear as sometimes it is so easy to read different thing than what writer is intended

I think that in rF2 tires are in a way much more clear to make, somehow much more logical, it is great improvement, still need to figure out how to translate realworld to tgm, still I try to learn them in rF1 too so your comments are well appreciated

edit: I have and will make updates to first post every now and then, so this is just heads up so you all know to check new stuff from there, added today more about springs and updated my calculator, happy modding!

[Stigasawus]

Ahh, life was so much less technical in the "olden days" when you did your best with soft springs, hard shocks & played with the tyre pressure...of course that was before recorded history...oops, showing my age. Oh well you cant fool most of you people some of the time.

[Vette4Life]

As an example, a Mini Cooper Coupe JCW (John Cooper Works, high performance version, 206hp) does 0.69G...

A Corvette ZR1 somewhere like 1.08/1.12G I reckon...

[jtbo]

Originally Posted by Stigasawus

Ahh, life was so much less technical in the "olden days" when you did your best with soft springs, hard shocks & played with the tyre pressure...of course that was before recorded history...oops, showing my age. Oh well you cant fool most of you people some of the time.

Reality is not so far from that these days either, I know lot of fellows in UK that do this drifting stuff, they take land rover shocks and put 90W oil in them, then put back of car that has rear springs of 10 000 - 11 000 of rfactor units, might sound familiar?

Yeah, in real world we always have to work with lot of limitations, when we build sim cars they tend to be too perfect, so that is why at least I tend to put bit adjustment to calculated perfect values, in cases where no data is available, like shocks for example.


I did notice that my damper calculations result bit higher than critical values for those rebound values, I remember that formula was same as used when designing damper rate for car by big companies, but I really doubt it should go above critical rebound, so I made bit of adjustments to formula and it results now critical damping value to rebound, which of course one can tune up with those percentages around calculated values.

I just need to evaluate change a bit more, then I can put up the new version if that is working.

Formula for slow rebound is like this:
Critcal*0.6666676*(3/2)

It was this:
Critcal*0.7*(3/2)

Maybe it has gotten rounded at some case, who knows, or maybe it is calculated to be bit over damping, too little information really around this subject too, but I know it is closely there

To get bump it is dividing rebound by 3-1.5 something from that range, bigger number is more comfy, sporty is around 2.

So original formula does calculate bump damping to be sporty as it is formula for sport and race dampers actually.

For street cars somewhat less damping is desired, rebound however should not be too far from critical, that is usually close as it gets dangerous if that is too far off (worn shocks), but bump damping for street car should be closer to 3, I think.

Rebound and bump travel is also important, my car's rear is so soft that it is not trouble to bottom it out while standing on bumper to get bump, then just lifting car up and measuring rebound, those alone make a lot of difference in handling, can mean difference between under and oversteer.

AFAIK, rebound and bump are measures from reference plane, bump defining where bump stop resides, rebound setting where is lowest position below reference plane that wheel can go, that is why travel is rebound + bump.
However there are some things that are not controllable.
Spring length is dynamic, it is adjusted automatically when you set your spring rate, so in case you have leafs at rear, there will be some imperfections as it does not act quite same way as coil spring does, same goes with progressive springs, which of course one can try to simulate with bumpstops.

Amount of travel can be then surprisingly small, my little Volvo has lot of travel compared to many other cars, especially at rear despite leaf springs.
Front:
BumpTravel=-0.145
ReboundTravel=-0.274
Rear:
BumpTravel=-0.10
ReboundTravel=-0.30

Amount of travel is correct, I did measure them just few days ago at -16C btw.
But location of bump stops is not there yet, from my current understanding real cars motion range includes bumpstops too, they are not really hard things, they can compress tens of millimeters without too much force, they are at work even when driving gently, at least in that car. Bump stops at front were around 50mm long and I could squeeze them to half, that is quite a lot and that is just what little I have in my fingers, so that might give bit of insight how bump stops can be.

So to add bump stop to front in real location I would need to do -0.145 - 0.05 = -0.195

Then I should try to adjust these so that it does compress same amount with same force as in reality, also bounce as in reality etc:
BumpStopSpring= // initial spring rate of bumpstop
BumpStopRisingSpring= // rising spring rate of same (multiplied by deflection squared)
BumpStopDamper= // initial damping rate of bumpstop
BumpStopRisingDamper=

For those I don't have formulas yet so that is something I have to hunt and figure out next.

I can tell you that it is almost impossible to set those by trial and error, trying to figure out if they act correct by motec and visual examination.

I could use default values of ZR, but it would be some 230kg off in weight and secondly is it certain that all cars are same and has ISI really done them to meet realworld or just make them to work as motion stoppers?
So only way to get these right and realistic is to figure out how to get rubber elasticity represented by these numbers,

Spring rate is perhaps easiest, put known weight to object and there are formulas how to calculate spring rate, damping is the problem, maybe calculating critical damping and setting some multiplier to represent how much bounce sledgehammer will get when whacking that poor piece of rubber. I think there should be some formulas for this somewhere, would sound better at least, but so far I have not found correct ones.

Anyway there is again bit more insight to how one can work towards realism when making a car to rFactor, so that at least there is some idea what one should consider to take account into.

[jtbo]

Originally Posted by Vette4Life

As an example, a Mini Cooper Coupe JCW (John Cooper Works, high performance version, 206hp) does 0.69G...

A Corvette ZR1 somewhere like 1.08/1.12G I reckon...

That is surprisingly low for that Mini.

Here ZR1 is 0.92-0.99 for those years represented by the list, they have improved of course a lot during years and tires have quite bit of to say also, also I remember C6 ZR pulling bit over 1G by some car show/magazine, but here are sporty cars:
http://www.angelfire.com/tn2/america...rs/TheList.htm

Here are some other kind of vehilces:

http://xenon.stanford.edu/~kpfleger/auto/handling.html

I remember not sporty VW Passat having 0.7X and that is not a sporty thing, so that Mini sound really really low, it is same as with Pontiac Aztec and that is one ugly minivan from my memory!

It can be possible still, but maybe it should be .96 for mini, typo perhaps?

[WildBill]

I thought it must be a typo as well---I've owned mini coopers and they handle very well usually.

[Vette4Life]

Might aswell been because it wasn't done on a skidpad but on a low speed figure eight ? Just realised that

Here:

Mini: 0.91 ( 0.88 w/TC on)

C6 ZR1 (Pre-2012): 1.06G
C6 ZR1 (2012): 1.13G

[jtbo]

Originally Posted by Vette4Life

Might aswell been because it wasn't done on a skidpad but on a low speed figure eight ? Just realised that

Here:

Mini: 0.91 ( 0.88 w/TC on)

C6 ZR1 (Pre-2012): 1.06G
C6 ZR1 (2012): 1.13G

That looks much better, imo.

Mini is considered sporty/better handling car than most average cars and 0.91 is not bad at all, but it is not a sports car level.

Corvette is there at the top, they silenced critics quite well when they launched C6.

From that alone we can conclude that having family econobox with sporty trim pulling over 1G is something we should not see in rFactor.

Ferrari is considered to be top sports car, but when you check skidpad results those are not much better than a Mini!

550 Maranello 0.93G for example and even I think that it is the car, especially convertible version is really nice to be so 'modern'. Because of such surprises it is important to try find some data from performance to get car even closely there.

Currently I'm having issues in finding skidpad results from old american cars, surely not first choice to try auto-x in such and not best cornering machines, but it has surprised me how little there is any facts about them. Probably somewhere in Hummer level or so, tires alone were quite different back then

[Vette4Life]

Yeah, old Muscle Cars should be somewhere in the 0.7G for the better handling one I guess ?

[jtbo]

Originally Posted by Vette4Life

Yeah, old Muscle Cars should be somewhere in the 0.7G for the better handling one I guess ?

Muscle cars skidpad

Not so horrible, 1965 GTO averages 0.71G being worst from that list, surely almost every passenger car since mid 90's can beat that, but considering the age and how we are told those cars can't make turns, it is not so bad.

Such era common sedans must have been quite bit worse than that then to create such image.

[Vette4Life]

Not bad indeed !

I was right then, in the 0.7G

[jtbo]

Just a note that I have now started a website where I put these bits of information and there will be also most recent versions of these in a future.

Address is http://finnsontrack.weebly.com/index.html

[mrpowcz]

Thanks, looking at it..