Is Suspension Tuning Backwards? - A Test with RX-8

[Kiljoy]

O.K looks like I need to take a step back and explain Wheel Rate and cpm.

Wheel rate is a measure of the amount of force required to deflect the road wheel a given amount, and is independent of the type of suspension, it's generally expressed in lbs/in.

Now the key here is deflection of the road wheel, the type of suspension will effect this calculation in respect to motion ratio's and spring angles.

Motion ratio defines the relative position of the spring with respect to the location of control arm pivot and the location of the wheel hub and the angle of inclination of the spring effects it apparent stiffness.

Check this for a diagram
http://www.swayaway.com/Suspension Worksheet.htm

The formula is
Wheel Rate = ( ( MotionRatio^2) * Spring Rate ) * sin(Spring Angle) (note the above link uses a slightly different formula, but the result should be the same)

cpm, (cycles per minute), if you read the Smithies site you will see that this is a calculation the find the Natural frequency at which an undamped suspension will bounce if a force is imposed on it. It's becoming accepted that optimum cpm for racing saloon cars is around the 120 - 150 cpm mark.

The reason for finding cpm? Well again as stated in Smithies site, is it provides a direct comparison between different cars. The fact that a cpm of around the 80 mark is used in passenger vehicles is that cpm relates to stiffness of the suspension, and for ride comfort, values of around 80 is accepted as optimum, but for handling and tyre grip 120 is considered to be more appropriate.

If more info is required I'm sure I can find alternative links for your viewing pleasure.

Cheers

 

[sukerkin]

Hi Kiljoy

The equations that you reference were ones that I first visited as they were the natural place to start(this was quite a while ago for me too, so you'll have to bear with any fluffyness in my recollections). Plus, as the very first reference to the subject that I Googled up was on the GP2 site and the math had already been done, I thought I'd save myself the trouble of having to think . It's nice to see that I wasn't the only taking this route and seeing someone else link to one of my original sources is heartening 👍.

However, in terms of unknowns from the game and the fact that I couldn't get them to produce results that made sense (again in-game) I took a whole different route through the Laws of Motion (angular frequency subset of simple harmonic motion), taking in Hookes Law and Critcal Damping along the way.

I never got Critical Damping to work with the game because we just don't know what the damper values mean. Which is a shame because the math is a doddle (English for "Very Easy" for our Trans-Atlantic viewers) - it's simply 2 * SQRT ((Supported Mass (kg) * Spring Rate (kgNM)).

The spring rates calculated from a desired frequency method I came up with is indeed glued together with the idea in mind that it is a system taking an input from an outside source (sometimes refered to as "Road Excitation" in papers on the subject).

If I remember at all correctly, the general impetous for my mathematic scribbling was an excellent paper on "Forced Vibration of Damped, Single Degree of Freedom, Linear Spring Mass Systems" from the Engineering Dpeartment of Brown University and David Apsleys papers on "Oscillations".

The general equation mangling came down to me trying to make use of what I could count as 'known' from the game with the genuine mathematics of suspensions. What might have given you the wrong impression about the use of PI is that as well as being useable as a measure of sinusoidal inputs it is also a definer of the completion of a spring system oscillation. One complete cycle is completed when Natural Frequency * Time = 2 * PI and can be used in the calculation of frequency in Hz by Natural Frequency/ (2 * PI).

To be quite honest, however, I have rather more good beer inside me right now than is good for my thought processes {:blush:} and I truely don't recall how I stitched all this together. I'll have to dig through my reference file and see if there's any rough notes in there from which I built my EXCEL calculator.

I'll try not to leave you hanging but I have an Iaido grading tomorrow so it's unlikely I'll be able to do anything before Monday as I'll be too busy swinging katana's around .

 

[Kiljoy]

Hi Sukerkin,

Glad you weren't upset at my post, as it sounds like you have come across the formula I've been using before.

Also sounds like we may have a similar approach to solving the handing in the GT series, I discovered Simithies site a few years ago not long after GT3 come out and found the shock tuning info invaluable, seem to remember a post of yours referred to this page.

But I'm not in a hurry for info as I've struggled with the application of cpm in GT since I started playing (way back in the days of GT2), and it gives me more time to digest the info I'm finding on the formula you posted... getting to old to spend my days with console games, I'm sure I have a life....

 

[rk]

OK, well thanks again for bringing me, and possibly a few other doofs, up to speed. It would be very nice to find a correlation between these equations and the physics in the game...

 

[sukerkin]

@Kiljoy

at your last statement and 👍 to the main body of your text.

I'd love to stop and chat as we sound to have a similar 'take' on this but beer and the lateness of the hour (plus my missus) call me to bed .

@Aarque - you're more than welcome from my point of view my friend. I'm pleased for any small help I've been to aiding you on the path of a deeper appreciation of GT's reality modelling in general and suspension tuning in particular.

 

[ZoomZoom]

Here is something I've noticed when tuning:

downforce seems to override most every tuning characteristic...

When you set your vehicle up with a ton of downforce, the changes you make to toe, camber, etc. have miniscule effect relative to the downforce setting...

To properly tune a vehicle as well as understand the settings better, were going to need to take off the rear wing and setup that last.

 

[Duke]

I did 10 laps with each setup at Tsukuba (in ABC order), then ran 5 laps each at Sears Point. I did find the default setup (A) to be easiest to drive - marginally. Truth be told the other two were nearly the same, just not quite as good.

In all three setups, the car understeered on the throttle and on the brakes. Even purposely driving badly, I could not duplicate Maturin's grid of results. The closest I got was a little lift-off oversteer on the downhill half of Sears Point. Otherwise, the car showed mild but manageable understeer at all times except coasting.

At both tracks I posted my fastest time with the B settings, which partly speaks to the Practice Effect and partly to the crappiness of the C settings. I want to go back and run a lot of laps with the A (default) settings and see if I can make that set faster.

Tsukuba (A): 1':04.853" Laps 1-10
Tsukuba (B): 1':04.281" Laps 11-20
Tsukuba (C): 1':04.648" Laps 21-30

Sears Point (A): 1':47.889" Laps 1-5
Sears Point (B): 1':47.041" Laps 6-10
Sears Point (C): 1':47.605" Laps 11-15

On Set A, I found the car to be about 90% neutral. It exhibited power understeer, mostly in the slow corners (Tsukuba being full of 2-gear crawlers, it was quite noticeable) but easily controllable. It also understeered moderately on heavy braking, though it would seem to turn in well enough on very light trail braking. The rear end felt very planted at all times.

On Set B, I found the car to be about 85% neutral. It exhibited slightly more understeer in slower corners, but it also gave a little kickback to the wheel on exit from the faster sweepers, which usually seems to indicate a little sliding out back.

On Set C, the car just didn't seem as happy. Braking understeer was worse, particularly when applying a touch at midcorner when carrying a little too much speed. It also gave more kickback during fast transitions and was relatively unstable the quick downhill side at Sears Point.

This leads me to believe that overall the suspension settings are somewhat reduced in effectiveness from GT3, and also that the Maturin effect does not exist with my driving. The stiffer rear did not create more understeer for me, and to me the softer rear only created oversteer where a lot of right-left oscillations set the back end to rocking. It did not seem to generate any oversteer in steady state or even into and out of single sharp corners.

 

[Kiljoy]

Sukerkin

Just thought I would add the general direction that wheel rates took me.

I started playing around with sprung/unsprung mass ratios to see if I could get the desired results from cpm.

I developed a formula that I played around with trying various ratios to estimate the sprung mass of the car, some of the info on Riley’s site started me off on this one.

The original base assumptions where that a car of curb mass = 300 kg would have an unsprung mass of 60 kg and a 2000 kg car would have an unsprung mass of 250 kg (using the formula it calculates at 273 kg). I then applied cmp calculations to the sprung mass of the car.

Varying results with this, but was interesting as lighter cars responded a little better to tuning Wheel Rates.

Here is the formula

Mu = 60 + (( Mc - 300 ) * 0.125)

Where
Mu is Unsprung Mass in kg
Mc is Curb Weight in kg

What this does is assume a 60 kg unsprung mass for the first 300 kg of curb weight, then assume that 1/8 (12.5%) of the remaining curb weight of the vehicle is attributable to the unsprung mass.


One for Greyout (or anyone who wants to respond)

I seen a post of yours re damping rates where you implied that bound values of 3 seemed best, I agreered with this until a couple of nights ago when I was playing with the XKR R - Performance Jag and found that it appeared to responded better to higher bound rates.

My initial reaction to this was that maybe the bounds are effected by vehicle weight. As the Jag is a heavyweight 1735 kg w/no lightening. It also reminded me of something I read from Carroll Smith re damping "The compression stroke controls the motion of the unsprung mass and the extension stroke controls the motion of the sprung mass".

Would be curious to know more from you (or others) as to whether you think that weight, possibly unsprung mass, does have an effect on damping. Or is it more likely that I just couldn't tell with a heavy car using a controller (most likely the case here).

Also curious as to maybe yours and others thoughts as to whether the game takes Sprung/Unsprung ratios into account.

Edit: Corrected the formula
Edit: Corrected values again!!

 

[Kiljoy]

Seeing as I'm onto damping...

...this was originally posted on a GPL site, not sure about the statement "...When the bump damper is too soft, the wheels will spend too long in the air..." but I've found the method works quite well in GT, at least it does for me.

The info posted was:

[start quote]

As originally recommended by KONI, the 'normal' way to set dampers in the 'real world' is as follows:

Set bump and rebound to their softest values.

Drive a few laps to get the feel of the car. Ignore body roll and concentrate on how the car feels over bumps.

Increase the bump setting on each wheel, one click at a time, to minimize upsets as the car travels over the bumps on the circuit. When the bump damper is too soft, the wheels will spend too long in the air after hitting a bump, and grip will be lost. You'll feel the car jump sideways or twitch a little when encountering mid-corner bumps. Increase the bump setting just short of the point where the car becomes 'hard' (in other words, increase the bump setting until the car becomes 'hard', then back off by one click). This 'backoff' point will probably occur sooner on one end of the car than the other. If this occurs, keep increasing the bump on the soft end until it too feels hard. Then back it off by one click. There are two factors that will affect the setting: how big the bumps are on a circuit, and how fast you are travelling over them. As you go faster, the bumps will be encountered at a higher frequency and with more energy. The more energy you get from the bumps, the stiffer the springs and dampers will need to be.

Leave the bump settings as they are.

Drive the car, paying attention to how the car rolls when entering a turn. Increase the rebound setting on all four corners, one click at a time, to make the car handle more positively, i.e. less limousine-like 'float'. (You have to experience this to understand it: driving around Zandvoort with all the dampers set to 3 bump + 1 rebound will demonstrate it well enough in GPL.) You're aiming to make the car turn in smoothly (no drastic attitude changes) without leaning excessively. Any increase in rebound beyond this point is unnecessary and may in fact be detrimental.

[End quote]

Never been able to find the original on Koni's site, but this may also be of interest...

http://www.koni.com/_cars/frame.html

...I only adjust the rebound to correct handling problems, as I believe that adjusting the bound causes problems elsewhere in the handling of a car once you have set the bound as above.

 

[sukerkin]

Hi Kiljoy

Interesting look into the effects of unsprung mass my friend. I never really delved there as I took the view that I would only be guessing at the ratio due to having zero information form the game on it. However, your application of logic doesn't seem to have any problems and sounds like you backed up your estimations with a deal of empirical test work 👍.

On the damping bound issue, I have generally worked from the rule of thumb that the total bound should roughly add up to the weight of the car in 100kg slugs e.g. a 1000kg car could have a Bound of 5/5. This is obviously only very rough and even I don't slavishly adhere to it but it does seem to have value as a 'finger in the air' starting point.

We obviously visit the same sites Kiljoy . I could see that a real world chat between us would probably be a bit dull; it'd apparently take the form of "I think this" ... "Yep, me too". I've read this at this site" ... "Yep, me too" . It's very reassuring when you find that anothers research has largely lead them to the same places and the same conclusions as yourself.

Of course, I agree entirely on your take of fine tuning the cars balance with the Rebound Dampers. A nice informative quote by the way. I've found the GL sites to be a valuable resource for 'game orientated' advice.

@Duke - excellent recounting of research, sir 👍. I'm glad to see that others are showing the same outcomes (or lack of definitive changes) that I found when I played around with the spring rates relative values.

Good news altogther over the weekend it would appear .

 

[rk]

Carroll Smith re damping "The compression stroke controls the motion of the unsprung mass and the extension stroke controls the motion of the sprung mass".

Would be curious to know more from you (or others) as to whether you think that weight, possibly unsprung mass, does have an effect on damping. Or is it more likely that I just couldn't tell with a heavy car using a controller (most likely the case here).

I once read that suspension engineers like to put a vehicle in the center of Newton's 3rd law. To do so removes the confusing issue of gravity and weight (which is being supported neutrally by the springs anyway). When, in this scenario, the vehicle is the static object, the Earth's surface is the intruder and the suspensions job is to prevent the Earth from upsetting the vehicle; it becomes glaringly obvious what effect sprung and unsprung weight have. The Earth will deflect ANYTHING with equal enthusiasm, whether it is carbon fibre or cold forged steel. So, if you take a 1500lb car and shove a 150lb suspension unit into it with force x, it seems clear it would take less compression damping to convert all that inertia into heat than if the suspension unit weighed 250lb, with a corresponding increase in its inertia. Similarly, if you carried an extra 1500lbs (sprung, of course) for "inertial damping" (star trek joke), you would have double the weight against which to leverage your compression dampers and it is logical to assume you could use more damping and still not "upset" the vehicle.
Based on the above, compression damping represents a direct relationship between sprung and unsprung weight.
Rebound damping is an entirely different kind of fish. When suspensions first evolved, rebound was the only stroke that was dampened. It was assumed that you wanted the wheel to clear the obstruction with as little resistance as possible; this pattern was the racing norm in England until well into the '60's. The rebound dampers mechanical job is to scrub stored energy from the springs and it has two vital parameters: it must convert all the energy imparted by any and every bump within one stroke (to prevent bounce unweighting) and it must not restrict the spring to the point it cannot fully extend before the next bump (suspension collapse).
The "first and second parameters" are likely what Carroll Smith was referring to about sprung mass.

 

[Greyout]

a little off topic, but I came across this picture and it made me dislike GT4 more

hows that for an unloaded inside rear 👍

 

[Duke]

That's my wife's car. I wish the Speedworld Challenge cars were included. But of course, that's an American series...

 

[dnomarz]

Hi Kiljoy

Interesting look into the effects of unsprung mass my friend. I never really delved there as I took the view that I would only be guessing at the ratio due to having zero information form the game on it. However, your application of logic doesn't seem to have any problems and sounds like you backed up your estimations with a deal of empirical test work 👍.

On the damping bound issue, I have generally worked from the rule of thumb that the total bound should roughly add up to the weight of the car in 100kg slugs e.g. a 1000kg car could have a Bound of 5/5. This is obviously only very rough and even I don't slavishly adhere to it but it does seem to have value as a 'finger in the air' starting point.

We obviously visit the same sites Kiljoy . I could see that a real world chat between us would probably be a bit dull; it'd apparently take the form of "I think this" ... "Yep, me too". I've read this at this site" ... "Yep, me too" . It's very reassuring when you find that anothers research has largely lead them to the same places and the same conclusions as yourself.

Of course, I agree entirely on your take of fine tuning the cars balance with the Rebound Dampers. A nice informative quote by the way. I've found the GL sites to be a valuable resource for 'game orientated' advice.

@Duke - excellent recounting of research, sir 👍. I'm glad to see that others are showing the same outcomes (or lack of definitive changes) that I found when I played around with the spring rates relative values.

Good news altogther over the weekend it would appear .

Thanks for the welcome! I am glad to have found this site!!

As far as springs being an axiom for under/oversteer...............it is without a doubt a major player in suspension (if you can't carry the load the load will carry you!!)!!
It is not the only component of cornering but intregal none the less (I'd like to see anyone try and corner a front engine, 300+ hp auto at speeds of even 50 mph or greater with incapable and weak front springs...........it aint gonna happen...........I do believe science calls this inertia)!!

Ducati 916............There is no substitute!!

 

[ZPEED]

I will agree that the suspension does not seem to lose grip in a spot-on realistic fashion when tuned extremely stiff, as it should in real life, let me make this clear, first off.

Here's my thoughts on what I think the game is doing.
Tires are only capable of handling a certain amount of lateral force before they slip. With softer, rollier suspension, the amount of lateral weight transfer is increased. In a turn, load is being focussed primarily on the outside tire. As the lateral forces on the outside tire exceed what it can effectively handle it may enter into slip. Additional inputs, such as acceleration, will submit the outside tire to further stressing. Meanwhile, with the load shifted to the outside tire, the inside rear may experience a loss of grip. Net result: you have oversteer.

I realize (especially after having read the links supplied by greyout), that this may hold little or no water in real life, but it is what i have witnessed within the game environment. Perhaps I am only repeating what has already been made known with this thread.

(i had something posted to this effect previously, and editted it a few times. that's where greyout got the quote that appears a few posts down)

This should be an interesting topic to watch, as the discussion progresses

That's because they ain't gonna tune every car the makers put on there and every different little way to get it perfect the cars are realistic when NOT tuned

 

[sukerkin]

:grits teeth:

Mantra - "Must not scorn the rude new member, must not scorn the rude new member"

Will power failing ... urge to scorn rising ... must log-off !!!!

 

[Duke]

:grits teeth:

Mantra - "Must not scorn the rude new member, must not scorn the rude new member"

Will power failing ... urge to scorn rising ... must log-off !!!!

Don't worry about it too much, sukerkin. After chasing him around mopping up the mess he made over his precious Opera S2000, we don't have much reason to get offended if somebody takes him down a notch or two.

 

[rk]

Well, just wanted to grab the lectern one last time and declare the matter closed, as this was the first day since starting that this thread dropped to the second page. It appears unresolved, although I think every participant came away with an answer for themselves and possibly a new prespective to boot. The thread had vastly more replies than any other, the only other thread that approaches the visits this one had is one where you are likely to find settings for your 1000hp Skyline. Perhaps Maturin's thread served a very useful purpose after all.

 

[Duke]

Well, off camera, a group of us have done a several hours' worth and several hundred miles' worth of testing each, then compared our impressions and notes. We have minor differences in which setup we found fastest, but our thoughts on car behaviour have all aligned pretty well.

We've been totally unable to reproduce Maturin's results.

 

[kingbobdole]

I know I'm a noob here but heres my 2 cents... and maybe someone can explain why so I can get the picture into my head so I can tune my car better to my driving style and get it fast....
Firstly, When I drive I do like to slightly drift the car, nothing fancy, just a hard late brake, back end cuts loose and a bit of gas as I leave while the car rights its self(oversteer while braking, under when accel) I was trying to do this using the norm school of thought... soft front= more traction, stiff rear=more slidin' That resulted in super braking understeer...Like it wouldnt turn understeer... ohh, I'm using a Subaru 22B (impreza) BTW and the settings were springs 6.6,12.5 I also have the diffs set up so its more like a RWD car then a AWD car.. I read this post and since I was "tunin' and racin'" I decided to swap the numbers so now its 12 front and 6 rear.. the car acts much closer to what I like.... I can turn in while braking, and the back end slides a bit... but that makes no dollars to me$$?? I kinda skipped over a few pages of this, read the first three and last three, did I miss the physics, or is the front and rear springs rate switched? I know the dives not.... the car dives less while braking now... with the 12 up front.

 

[sukerkin]

Hi Bob

The short answer would appear to be that, no, the Spring Rate effects are not reversed.

What seems to be happening is that the way they affect the cars handling is more complex than before but can be visualised more simply if you think of it as determining where the weight distribution sits (the stiffer end seeming to carry more weight).

In the end, it will come down to how you like the car to handle (as ever) and how you drive (the game's physics take much more account of smoothness in control than before).

 

[Pungent]

Ok, I decided to give this a try too. I went and bought a new RX-8, and picked up the Racing suspension for it. I then tuned two sets (A&B). I set A to 1/1 for bound/rebound on the back, and left the front at 8/8. I left springs alone, to count that out, since the "drama" here is whether stiff back = oversteer in GT4, so if this were the case you do not have to touch the springs at all to see that, it can all be in the shocks. I also dropped stabilizers front/back to 1 and Camber to 0. Toe is 0. All of this is to simplify the effect of these components. So the only difference is the shocks. Set B was same except the shock settings were reverse of A. Took it to High Speed Ring, a course where you have a lot of banked turns where over/understeer will be obvious. Results:

Set A (soft back): Lots of difficulty turning, fairly bad understeer. Turning left/right is pretty sluggish.

Set B (soft front): Oversteer. Turned on a dime.


SO, I would say that PD did get the physics right. Now, the question remains, how did you get the results you did?

While you are very correct in your reading, that a stiff backend gets overloaded quickly and results in oversteer, what you are forgetting is that this is a 'rule of thumb', 'all conditions equal'. In your setups, the soft backends also had low spring rates, which resulted in a massive weight transfer. the car pitched/rolled to the back tires much easier. As a result, there is more weight on one tire, and grip loss occurs.

****EDIT: THIS BELOW MAY BE SERIOUSLY WRONG. I'M STILL TRYING TO WRAP MY HEAD AROUND THIS*******
In your other example, the soft front and insanely stiff rear resulted in understeer. The reasoning is, while the backend absorbed a lot of the force, the front was also weak. The forces pushing on the car to the one side are mostly being handled by the stiffer rear spring. However, a spring pushes the force acting against it toward its center axis for the system, in this case the car. The stiffer back spring pushes this force easily against the center of balance, dumping a lot of force toward the front. The front spring is not strong enough to cope with the force. Therefore the front tires lose grip, but now the car is not turning inward. To steer you must have grip in the frontend. The result is understeer.

All this is really just an improvement to the physics model in GT4. It adds more variables to the calculations. The standard "Laws of Suspension Tuning" still apply. But in extreme cases they break down, even within the Real World

   Front:                                   Back:
   Soft-----------------Hard     Soft-----------------Hard
1  |=-----------------------|     |-----------------------=|
2  |------=-----------------|     |--------------=---------|
3  |---------------=--------|     |-------=----------------|
4  |-----------------------=|     |=-----------------------|

1) Understeer
2) Oversteer
3) Understeer
4) Oversteer


I hope that makes sense. I'm having a hard time putting this into words. Please point out any errors you see. But the sum of it is, don't use totally extreme settings and expect it act the same but to a higher degree.

If your car is understeering, stiffen the rear spring to a higher degree than the front, but don't overdo it. Keep the setting sane and the car reacts the way you expect.

 

[sukerkin]

A very sane post, Pungent 👍. Your final paragraph, specifically in fact your final sentence, was about the best distillation of all we've written on this subject so far.

About the only thing in the first section (from my initial read) that might need more clarity is that whilst the roll/pitch of the car body on the springs may indeed cause oversteer-like handling it isn't because it's getting more weight transfer in the traditional sense. A stiffer spring pair carries and transfers more weight compared to a softer set. Have a look through the threads on this, particularly searching for M-Specs good illustration of how this is so. Mind you, the rest of your post suggests you understand this just fine anyhow, so if it's un-necessary advice (or worse, patronising), I apologise.

 

[CombatWombat]

I've done some *very* unscientific testing on various cars (aka I played the game).
What I'm finding in my own personal experience, is that suspension tuning doesnt make any difference at all. For me. Maybe its my driving style?

I try little increments of 1-2 clicks on springs and shocks and such, and there is no difference in the percieved feel of the car, nor in lap time. I can run consistantly within +/- .300 depending on track, and this doesnt vary no matter how zany the setup. I've also tried drastic changes. Like sliders maxed one way or the other, and it'll maybe hurt my times a few tenths. Nothing drastically uncontrollable I would expect from 15+ (SOMETHINGS?!?! Degrees? RADIANS?! Fluffy Bunny Rabbits???) of camber.

A specific example, is that currently I'm trying to setup my Camaro LM to have more mid/late corner oversteer, as it has a tendancy to melt the front tires on extended runs. Everything I've tried has failed to do ANYTHING at all. I've tried spring adjustments, and loosening of the LSD mostly, figuring that would help reduce the "on throttle" understeer. Nothing.

Am I crazy? Yes probably. Yet in every other sim I've played (PC only, I bought the PS2 JUST for this game) the tuning can make drastic changes to the car; to the point of making it entirely undrivable. (Viper Racing, SCGT, GPL, LFS is the sort of game I'm comparing to). Does GT4 automagically 'adjust' the slider Min/Max ranges so that you cant "hurt yourself"? (Safety scissors tuning for console junkies?) There arnt units on nearly ANYTHING, so maybe, its hard to tell?

 

[rk]

I've done some *very* unscientific testing on various cars (aka I played the game).
What I'm finding in my own personal experience, is that suspension tuning doesnt make any difference at all. For me. Maybe its my driving style?

...and of course you've disabled asm....?

 

[CombatWombat]

...and of course you've disabled asm....?

Of course.

 

[Pungent]

A specific example, is that currently I'm trying to setup my Camaro LM to have more mid/late corner oversteer, as it has a tendancy to melt the front tires on extended runs. Everything I've tried has failed to do ANYTHING at all. I've tried spring adjustments, and loosening of the LSD mostly, figuring that would help reduce the "on throttle" understeer. Nothing.

Push the LSD Accel setting up. I find the the higher the setting the more the car grips on the outside tire when you stomp the gas mid-exit on a turn. Too much and its enough to spin you out.
"Rule of thumb" settings for most cars LSD:
Initial Torque: 10-17 Accel: 35-52 Deccel: 20-34
Those are the ranges I usually keep the setting within. For something like the camaro, being somewhat heavy and slightly powerful I'd probably use 15/45/25 on it. I'm just guessing here, since I don't have one of those and can't test this setting, but that is what I would put as my initial setting and test that out.

Suspension I'd set it back to default, push the rear spring rear up a slight bit, drop the front shocks to 5/6 (bound/rebound), set rear to 7/8, set camber to 2.5/1.5, stabilizers to 2/5. This is all just guessing since I haven't driven that car in game. But try it out, that may help a bit.

I'm not certain why you don't see the difference, I was playing with the tuning on both my MX-5 and Lancer, and was trying out extremely stiff spring and shock settings (front and rear), and the cars became bricks. There is a noticeable change in the turning ability that I saw in doing that. But again you have to remember that even the best suspension can't help some cars Some cars just turn like crap, and there's nothing you can do about it. In GT3 I spent an ungodly amount of time trying to tune a Viper to turn and finally gave up.

 

[Pungent]

Ok, this problem has been burning in my mind all weekend now. When my brain gets a challenging problem it just won't give up until it has some solution. So, here is the results I've come up with.

About the only thing in the first section (from my initial read) that might need more clarity is that whilst the roll/pitch of the car body on the springs may indeed cause oversteer-like handling it isn't because it's getting more weight transfer in the traditional sense. A stiffer spring pair carries and transfers more weight compared to a softer set. Have a look through the threads on this, particularly searching for M-Specs good illustration of how this is so.

This is correct, and applies to most cases, however it is a bit simplistic. First, lets clarify exactly what a spring does:
A spring, when compressed, pushes the force acting against it in two directions. In the case of a car, it pushes the force back toward the body, and into the shocks. So, when weight is transferred to it, it will push down into the tires, which usually results in overloading that tire where it is stiffer.
HOWEVER, the car is a system of springs. As such, there is a 'balance' point where they all work towards (as illustrated in the guides). A spring will push the weigh towards this point. The stronger the spring the further away from itself the point is, affected by the strength of the other sets. To clarify the meaning of 'push weight towards', think about it as the point the spring braces itself against. If this point is too far forward, the stiffer spring braces itself against that point, therefore more force is going to directly effect the front tires. But how is this so, if the front spring is weak and isn't able to push this force against them? The fact is that the weak front spring/shocks are becoming overloaded themselves. When this happens, what do you have? Basically a solid steel bar. The body comes down, overloads the front suspension, and body comes to rotor/tire directly, meaning ALL force acting on that end will go straight to the tire, no 'cushioning', thus overloading them.

Also, I do agree with the 'stronger accepts more weight transfer' there is a problem with believing that to always be true. I tried to put this into words but then deleted it as it was getting confusing even to me. Basically, a stronger spring will accept more weight, however it cannot compensate completely for the weaker end if the transfer is toward the weaker end. Quick example is, strong front/weak rear, ratio 10:1. Weight shifts to the back ( accelerating ), the front can prevent some weight moving in that direction but not at a 10:1 ratio. The difference ratio must be closer to 1:1 in order to have the stronger set compensate. The stiff front cannot prevent the weight from shifting that much to the weaker rear. I wish I could find the logarithm to illustrate this, but I haven't been able to find it.

SO, to recap. Use spring settings for balance. It is perfectly acceptable to have a stiffer front setting than rear, in order to set the weight balance for an unbalanced car. This is the primary function of the spring rate, so try to keep it close to the default for the suspension set ( when you apply a tunable suspension kit it defaults to balance the car front with rear ). If you want to stiffen it try to keep increases equal on both ends. If you do stiffen/weaken one end try to not overdo it, and remember that you are effecting the balance point for the car in doing so. Another point to remember is that you should really only stiffen one end if you are getting eccessive pitching. Some pitch is IMO good, too much or little is bad. Typically I set it so that the car doesn't pitch hardly at all in acceleration, and pitches a bit in braking.

Use shock settings to set the oversteer/understeer characteristics of the car. While this is also decided by the balance of the springs as well, you should try to do most of the tuning here in the shock settings.

Again, I want to say that I hope this makes sense. It does in my head but not everyone thinks the way I do so it could be very confusing to some others. I strongly encourage someone to take up some points here and argue that I'm wrong somewhere so that I can try to explain that part further. I actually like to argue because it helps me improve my own understanding of something sometimes.

 

[Bad760]

And I thought this thread had died a natural death

I have come to the conclusion that the spring rates aren't reversed but the physics engine is alot more sophisticated than the previous games and you need to have a lot lighter touch on the controller to drive the cars fast.

As long as you raise the spring rates equal amounts to get the car stiffer and then change each end in small amounts to get the balance you want then all is well.
It is only when the front and rear rates are drastically different that you get into trouble, why you would want to do this in the first place is beyond me anyway.

One thing I think people forget is that the front and rear suspension don't work separately, each end effects the other as they are connected by a relatively stiff car.

 

[CombatWombat]

Push the LSD Accel setting up. I find the the higher the setting the more the car grips on the outside tire when you stomp the gas mid-exit on a turn. Too much and its enough to spin you out.
"Rule of thumb" settings for most cars LSD:
Initial Torque: 10-17 Accel: 35-52 Deccel: 20-34
Those are the ranges I usually keep the setting within. For something like the camaro, being somewhat heavy and slightly powerful I'd probably use 15/45/25 on it. I'm just guessing here, since I don't have one of those and can't test this setting, but that is what I would put as my initial setting and test that out.

This seems counter-intuitive to me, and doesnt really jive with the behavior of my real-world car, although I guess it makes sense when you figure the inside tire will have less load on it, and thus more torque will be transmitted to it in a purely open differential, causing the vehicle to yaw away from the intended path.

My findings on R/C cars and my 88 Mustang, is that locking the drive wheels together (solid axle, and when the posi locks up respectively) result in two things depending on condition.
1) It tries to drive the car straight foreward as the two are now forced to rotate at the same speed. Maybe this is the result of the additional forceward acceleration of BOTH wheels working causing a transfer of weight away from the front end?

2) If traction is broken, it results in alot of oversteer, as now BOTH tires are definitively spinning. It's no longer a one-wheel-peel.

Well..I'll fidget more with this. Although I'm still fairly convinced that the settings do very little in terms of car handling. I'll have to try some kind of blind test with someone making adjustments for me.