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

  • Thread starter Maturin
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M

Maturin

99
Well, since my question in Greyout's thread got swamped by a mod/poster war, I'll have to post this here. I think that, in my copy, the suspension tuning goes the opposite of what is canon on this forum. That is, that softer rear settings, induce MORE oversteer (which is opposite of what is canon on this forum). Do I just have a bugged copy, or is something else happening?

I did the following test, and I can duplicate this with any car. There are three settings, and the results are below each. I absolutely encourage any of you to duplicate these settings, and try to duplicate my results, or debunk them.

The settings will be done across, so you can see the differences easily, and they'll go SETUP 1 (which is Default Settings), SETUP 2, SETUP 3, and finally below the settings, the results.

I made sure to take the corners as I always do, and for the big banked left-hander, I took it at 2nd Gear, around 61-63MPH, for consistency.

TEST

Car: RX-8 Type S(J) - FR 285HP (Completely Stock except for Racing Suspension)
Tires: S2
Track: Trial Mountain

SETUP 1 SETUP2 SETUP3

Springs f10/r10 f10/r15 f10/r6
Height 120/120 120/120 120/120
Bound f8/r8 f6/r8 f8/r6
Rebound f8/r8 f6/r8 f8/r6
Camber 2.0/1.0 2.0/1.0 2.0/1.0
Toe 0/0 0/0 0/0
Stability 4/4 4/5 5/4

RESULTS:

SETUP1 (Default): Slight oversteer, nearly neutral
SETUP2 (rear stiffer): Understeer, in all turns.
SETUP3 (rear softer): Oversteer, in all turns. Braking, mid-turn, exit


My question is, shouldn't Setups 2 and 3, have REVERSED results?
 
I'll have to try this when I get home, but I certainly hope not...

even if PD WANTED to make up their own physics, their scrolling text at the bottom disagrees with your findings, and agrees with normal convention.

edit: one thing that I am considering is that PD's engine will not allow the inside tires to lift off the ground from cornering forces. (although they would in GT1...)

when the droop limit is hit, it may simply stop there and start compressing the other side more.

If the droop limit is hit on the inside rear, it could then start overloading the outside front. (Kinda like a reverse bumpstop?)

I hope this is all very very wrong though. Even then however, I am disapointed to see that all the cars keep all 4 wheels solid on the ground regarless of suspension tuning.
 
I just asked a friend of mine to give it a shot.

He softened up the rear of the prelude, and stiffened up the front. He said it is the "oversteer king"

This is very bad.

Until I can go home and try this myself, I take back anything good I ever said about GT4 physics.
 
Most cars in GT1 and GT2 are like that ... Soften up the rear and stiffen up the front without increasing the rear stabilizer bars and your rear end will be swinging around very easily, regardless of drivetrain ...
 
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
 
it is a basic fact in all facets of the automotive industry, be it production cars or race cars, that the stiffer end of the suspension generally will let go first.

There is more weight transfer at the stiff end then the soft end. There is nothing to debate about this.

Just about every front wheel drive race car in North America has spring rates in the rear that double or MORE the rate of the front.

static forces
500 500
500 500

left turn with a stiff rear
550 450
900 100

rear will let go first. this has ALWAYS been the case.

references:
http://track-days.org/page8.html

http://www.timskelton.com/lightning/race_prep/suspension/corrections.htm

http://forums.nasioc.com/forums/archive/index.php/t-436126.html

http://www.turbomopar.com/handling.html

it goes on and on.

the world knows how this works. A STIFF REAR UNLOADS THE INSIDE REAR, OVERLOADS THE OUTSIDE REAR, OVERSTEER RESULTS.
 
Going Faster! Mastering the Art of Race Driving
"All other things equal, going to a stiffer spring will increase resistance to roll and absorb more of the load transfer at the end of the car on which it is installed.

At the front, going to a stiffer spring (higher spring rate) will increase understeer. Going to a softer spring (lower spring rate) will decrease the roll resistance of the front, moving the cornering balance away from understeer.

At the rear, a stiffer spring increases the tendency toward oversteer, while a softer one goes in the opposite direction, decreasing the oversteer tendency and increasing the tendency toward understeer."
Click to expand...

I could quote many more sources, but I think Skip Barber's own publication is beyond reproach, don't you guys?

Okay.. maybe one more. http://www.wtrscca.org/tech.htm

BUT in the interest of understanding GT4, I will try to replicate Maturin's experiments and see if I get the same results.

In addition, the tendancy for a car to over-or-understeer is just that. A tendancy. It is possible for car to exhibt BOTH tendancies, depending on a variety of factors. Let's not assume that because we can demonstrate one instance of a contradiction, it means the whole canon should be thrown out the window.


M
 
Normally front springs for cars have a stiffer spring rate because of the weight of the engine.

There's nothing really weird about having stiffer front springs thats how they SHOULD be.

So you should retest with the same spring rates for all and just adjust the bound and rebound settings.
 
JaeTea
So you should retest with the same spring rates for all and just adjust the bound and rebound settings.
Click to expand...

It exhibits the same behavior. In fact, usually I keep the front springs slightly stiffer, but mostly even, because I figure they take more weight under dive, so it should be somewhat even. Then I go to work on the springs.

Fact is: In GT4, less stiffness = More Grip. Theory is one thing, the game's reality is quite another.
 
Greyout
A STIFF REAR UNLOADS THE INSIDE REAR, OVERLOADS THE OUTSIDE REAR, OVERSTEER RESULTS.
Click to expand...

Well, I don't really care how the real world works, just what works in GT4, and all I know is that the softer you make the rear, the easier it swings around. In fact, before I started reading this forum, I tuned the Alpine (the "boxier one"), which is an undrivable oversteering RR beast, by increasing the rear suspension, and softening the front, to their maximum, and it drove like my Focus.

Haven't you tried your theory in the GAME yet? It doesn't work.
 
awdrifter2
I have to agree with Maturin here, softer rear does make the car oversteer more in the GAME. I guess they fcuked up the physics on this. When I softed the rear suspension on my 91 Skyline GT-R N1 and Silverado SST Concept, it really made those cars driftier.
Click to expand...

PD actually KNOWS this, which is why if you buy the Supra RZ (used car), the natural oversteer settings, since the car is notoriously oversteer prone, as DEFAULT settings are f15/r7 on the springs. Which makes me wonder if the experts on this forum really know what they're talking about and aren't forgetting something.
 
I've done some tests too, with an NSX, to start with a rather neutral car, and yes, in some cases softening the rear does create more oversteer.

For stabilizer though the theory seems to works, softer rear / stiffer front usually reduces oversteer.

The effective changes of suspensions settings under mixed conditions of braking/cornering/accelerating/ and different weight distributions looks rather complex to have one-size-fits-all recipe to handling issues.

For the theory advanced so far, everything looks fine to me except the part where more weight is supposed to be transferred to stiffer shocks at the rear. I thought that the same amount of weight would be transferred, only with different travel / timing, the stiffer spring obviously bouncing back more quickly than the other, increasing the force exerced on the wheel for a given time, and also its peak force. I though the softer spring would do the same work, only over a longer period, with a smaller peak force exerced on the wheel.
 
jpmontoya
For stabilizer though the theory seems to works, softer rear / stiffer front usually reduces oversteer.
Click to expand...

I get the opposite result. Softer rear/stiffer front increases oversteer. Tried it at 1/7 7/1 3/5 5/3 on Supra RZ and RX-8 S(J)
 
awdrifter2
Now that I think about it, it might have something to do with the camber. I have 0 camber in the rear for both my Skyline and the Silverado. So a softer rear spring would make the tire contact the ground less. I'm going to test it out tomorrow. Set high camber in the rear, see if it grips more.
Click to expand...


That would be true regardless of the suspension stiffness wouldn't it?

(edit, "irregardless" isn't a word, is it? Ironical that.)
 
I think that this is being aproached in too broad of terms. Yes generally speaking all things being equal, the stiffer end of a car tend to lose grip first, but there are way more factors involved than just spring, damper, and even anti-roll rate.

In real life things like camber curves and bump steer have as much to do with the way a car handles as travel rates do. It's true that if you soften the suspension it should have a higher limit of adhesion, but only to a certain point, if you soften it to the point where it begins to gain camber, positive or negative, at a rate that is disproportionate to the angle of body roll the increase in camber will cause a decrease in lateral adhesion.

A few months ago I wouldn't have thought that PD could ever try to simulate something like a camber curve for a video game. Then I started building GT3 hybrids. On some of the hyrbids I built with huge amounts of suspension travel and really soft spring rates you can see the camber curves in action, the car gains and loses camber in bounce and rebound, and the arcs the wheel makes through it's travel is different from front to rear on the same car. I'll have to go back and check again, but I believe one even went through two cycles where it went from negative camber at full compression, to 0 camber at the static ride height, through a brief moment of positive camber and back to negative at full jounce, simulating a camber curve for an unequal length control arm setup, but I'd have to look again to be sure.

I realize that this is making an assumption that just because it is modeled means it has an affect in the physics engine, but if it doesn't than why go through the trouble to model it?

Could it be that what people are interpreting as a screw up by PD could be a staggering dose of realism added to GT4?
 
bfifteenv
Could it be that what people are interpreting as a screw up by PD could be a staggering dose of realism added to GT4?
Click to expand...

I'm certainly not the one saying anything about PD. It's some people on this forum who are wrong when it comes to their writeups on how it works in the game. I mean, we have TWO guides at the top, that, if one were to follow, would screw up your driving. If those guides want to include "camber curves", great, but until that point comes, in GT4 Softer Suspension = Less Grip.
 
Maturin, I know that you have experimented and have proved to your own satisfaction that what you are saying is 'fact'.

I wouldn't dispute that you have empirical evidence that softening the suspension at one end reduces rather than increases the grip at that end. However, to then project hostility onto the established 'laws of tuning' is probably not the best way for a new member to win friends and influence people.

The threads you deride above are not the result of random scribblings but of years of research and testing by a number of us.

It may thus be a better idea to try and think why you're getting the results you are rather than assuming that everyone else has simply got it wrong.

Suspensions are a complex piece of engineering with an inordinately large number of variables involved and it may well be that what you are seeing as an in-game consequence is the result of an amalgamation of factors instead of just one (as bfifteen v hinted at earlier).

Don't take this as a 'flame' as it's not intended as such but you'll find people will take more of your input on-board if you're a bit more polite about it.
 
Maturin
Well, since my question in Greyout's thread got swamped by a mod/poster war, I'll have to post this here. I think that, in my copy, the suspension tuning goes the opposite of what is canon on this forum. That is, that softer rear settings, induce MORE oversteer (which is opposite of what is canon on this forum). Do I just have a bugged copy, or is something else happening?

I did the following test, and I can duplicate this with any car. There are three settings, and the results are below each. I absolutely encourage any of you to duplicate these settings, and try to duplicate my results, or debunk them.

The settings will be done across, so you can see the differences easily, and they'll go SETUP 1 (which is Default Settings), SETUP 2, SETUP 3, and finally below the settings, the results.

I made sure to take the corners as I always do, and for the big banked left-hander, I took it at 2nd Gear, around 61-63MPH, for consistency.

TEST

Car: RX-8 Type S(J) - FR 285HP (Completely Stock except for Racing Suspension)
Tires: S2
Track: Trial Mountain

SETUP 1 SETUP2 SETUP3

Springs f10/r10 f10/r15 f10/r6
Height 120/120 120/120 120/120
Bound f8/r8 f6/r8 f8/r6
Rebound f8/r8 f6/r8 f8/r6
Camber 2.0/1.0 2.0/1.0 2.0/1.0
Toe 0/0 0/0 0/0
Stability 4/4 4/5 5/4

RESULTS:

SETUP1 (Default): Slight oversteer, nearly neutral
SETUP2 (rear stiffer): Understeer, in all turns.
SETUP3 (rear softer): Oversteer, in all turns. Braking, mid-turn, exit


My question is, shouldn't Setups 2 and 3, have REVERSED results?
Click to expand...

I'm not sure i see why the settings are backwards.

In going from setup 1 to setup 2, you are reducing the bound and rebound in the rear. Braking into a corner, since the rear rebound is softer, the weight doesn't transfer to the front (turning) wheels as quickly. Accelerating out of a corner, since the rear bound is softer, the weight transfers backwards more quickly, away from the front wheels. This is why the car now understeers going from setup 1 to setup 2. (both in and out of the corner)

I think the bound/rebound should be the first place to start when correcting over/understeer, as it has the most impact. Also its probably easier to adjust one thing at a time in the setups your testing.

My explanation of the weight transfer may not be fully correct, but the bound/rebound settings you have chosen will deffinately promote understeer.
 
it has been established that in real life, stiff rear / soft front causes oversteer. If you disagree with that, please do some more reading before you post in this thread. There is nothing on that subject to debate. If you think that PD has somehow proved the world wrong and got the physics right, read the scrolling text about the spring rates. Even THEY say that stiff in the rear = oversteer, stiff in the front = understeer.

As a test this morning, before I left for work, I took my trusty prelude in the game and set the rear spring rates at 3.8, and the front springs at 17.

everything else was even front and rear, except for the dampers which were set to match those spring rates. (soft rear, stiff front.)

2.0 degrees of camber at each end

0 toe at each end

4 sway bar at each end.

The car oversteered so much that at Full throttle in second or 3rd gear, the car drifted all the way around the corners, with all 4 tires smoking and about a 45 degreee slip angle.

One of three things is the case:

1) someone in charge of something at PD royally ****ed up, and the slider on the spring stiffness scale is backwards - as the slider increases, the spring rate is actually decreasing. The car DID seem to exibit a bit more body roll up front with my superstiff springs, but I may have just been imagining it - but its POSSIBLE this is the case. If this IS the case, the question is, what about the damper slider? or the sway bar? We know the camber slider is correct at least...

2) The physics model created by PD has a serious, UNINTENTIAL flaw (again, read the descriptions in the game!).

Either one of these two is equally possible.

I will be doing some testing tonight with each individual variable to try and detirmine whats going on. For those that care, be sure to check back & please give your $0.02 worth. For those that don't understand this, and think that a soft rear setup should REALLY oversteer, don't bother.
 
sukerkin
However, to then project hostility onto the established 'laws of tuning' is probably not the best way for a new member to win friends and influence people.
Click to expand...

I'm not projecting hostility on the laws of tuning, i'm projecting some well-founded criticism and amazement that the posters who wrote such articles as "The Pocketguide to GT4 Tuning" evidently NEVER tested it in the actual game. As if they just assumed it worked.
 

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