spring rate value is not equal to spring stiffness?

I have something that need to be tested in GT4 too.

In GT2 spring rate is related more to car cycle per minutes (cpm) when bouncing, that is, lower spring rate value will give less cpm. What's funny is, on the same spring rate value, the lighter the car, the lower the cpm. I do quick test on Subaru 360 and Skyline GTR R32.

on 2.0/2.0 spring rate the cpm is 60 for subaru, 98 for skyline.
on 20.0/20.0 spring rate the cpm is 114 for subaru, 170 for skyline.

So, spring rate value in GT2 definitely not related the measurement of the spring (lb/ft kg/mm) but related to how the spring affect car natural frequency. Because if 2.0 is a measurement of spring stiffness, a 2.0 SR skyline must have lower cpm than a 2.0 SR subaru. Heavier car will bounce less using the same spring.

What make me suspect that GT4 also have the same behaviour is because subaru 360 wallow more than a Land Rover Storm.

For why lighter car has lower cpm, I guess PD forget to correct it.

Tester invited, remove the damper and stabilizer when testing.

sucahyo

I have something that need to be tested in GT4 too.

In GT2 spring rate is related more to car cycle per minutes (cpm) when bouncing, that is, lower spring rate value will give less cpm. What's funny is, on the same spring rate value, the lighter the car, the lower the cpm. I do quick test on Subaru 360 and Skyline GTR R32.

on 2.0/2.0 spring rate the cpm is 60 for subaru, 98 for skyline.
on 20.0/20.0 spring rate the cpm is 114 for subaru, 170 for skyline.

So, spring rate value in GT2 definitely not related the measurement of the spring (lb/ft kg/mm) but related to how the spring affect car natural frequency. Because if 2.0 is a measurement of spring stiffness, a 2.0 SR skyline must have lower cpm than a 2.0 SR subaru. Heavier car will bounce less using the same spring.

What make me suspect that GT4 also have the same behaviour is because subaru 360 wallow more than a Land Rover Storm.

For why lighter car has lower cpm, I guess PD forget to correct it.

Tester invited, remove the damper and stabilizer when testing.

Click to expand...

And how exactly do you propose that this is measured in either GT2 or GT4 (or any in the series, given that we can't remove the dampers or anti-roll bars from the test?

Regards

Scaff

Just one question Sucahyo... has it occurred to you that the spring rate might actually be the same thing as the spring stiffness, but the 2.0 is a different value for different cars? The cars may have different ranges of stiffness and the spring rate value only sets the point in that range.

If I got your idea totally wrong, I apologize.

- R -

Greycap

Just one question Sucahyo... has it occurred to you that the spring rate might actually be the same thing as the spring stiffness, but the 2.0 is a different value for different cars? The cars may have different ranges of stiffness and the spring rate value only sets the point in that range.

If I got your idea totally wrong, I apologize.

- R -

Click to expand...

I assume you are right. 2.0 would be harder on a Group C car, than it is on let´s say a Charger. Apples and oranges!

Scaff

And how exactly do you propose that this is measured in either GT2 or GT4 (or any in the series, given that we can't remove the dampers or anti-roll bars from the test?

Click to expand...

If we can't hack it, we minimize it. We still can count it based on how much the car cycle up and down in 5 second, and multiply it by 12. IIRC GT4 Subaru 360 wallow 1 cycle per second on 1.5 SR, equal to 60cpm, maybe lower.

I hack GT2.

Greycap

Just one question Sucahyo... has it occurred to you that the spring rate might actually be the same thing as the spring stiffness, but the 2.0 is a different value for different cars? The cars may have different ranges of stiffness and the spring rate value only sets the point in that range.

Click to expand...

That is what I mean, 2.0 is different spring rate value for each car, but it will give almost the same natural frequency for each car. but it can also from other possibility since in GT2 heavier car have higher cpm.

I assume the car with weight in between skyline r32 and subaru 360 will have in between cpm too. 2000 lbs car have 80 cpm bounce, etc.

Team666

I assume you are right. 2.0 would be harder on a Group C car, than it is on let´s say a Charger. Apples and oranges!

Click to expand...

If the spring rate value is the same thing as spring stiffness, the 2.0 have to be the same for different cars. I mean 2.0 as in 2.0 lb/inch have to result in lower cpm on heavier car.

Just like the quote from smythee:
"For instance, in the graphs below, a 50 lb per in. increase in spring rate for the 1000 lb per wheel vehicle, achieves only about half the spring frequency increase we get with the 50 lb per in. increase for the 300 lb per wheel vehicle."

So, with the same spring stiffness increase heavy car will have cpm less than light car.


If 2.0 is a different value for each car that would mean 2.0 would have no relation to real life 2.0 spring stiffness that measured in lb/inch.


I don't think PD would use a spesific variable or multiplier for each car. It would be better if they just use car natural frequency algorithm for spring rate value.

Some nice explanation about cpm:

Robert Q Riley

The ride quality normally associated with the vehicle's response to bumps is a factor of the relatively low frequency bounce and rebound movements of the suspension system. Following a bump, the undamped suspension (without shocks) of a vehicle will experience a series of oscillations that will cycle according to the natural frequency of the system. Ride is perceived as most comfortable when the natural frequency is in the range of 60 to 90 cycles per minute (CPM), or about 1 Hz to 1.5 Hz. When the frequency approaches 120 CPM (2 Hz), occupants perceive the ride as harsh. Consequently, the suspension of the average family sedan will have a natural frequency of about 60 to 90 CPM. A high-performance sports car will have a stiffer suspension with a natural frequency of about 120 to 150 CPM (2 to 2.5 Hz).

Click to expand...

I don't know wether PD make 120 to 150 CPM as the best handling value for spring rate or not.

From LDS - Basics of Structural Vibration Testing and Analysis






I am saying that spring rate value in GT is W in equation, not K.

from equation:
k = mW^2

in hertz, don't know the real measurement of k

skyline R32 on 2.0 spring rate
k = 2993lb * 1.63 * 1.63
k = 7952

subaru 360 on 2.0 spring rate
k = 936lb * 1 * 1
k = 936

skyline R32 on 20.0 spring rate
k = 2993lb * 2.83 * 2.83
k = 23970

subaru 360 on 20.0 spring rate
k = 936lb * 1.9 * 1.9
k = 3378

This stinks of "10 is softer than 1." 👎
And based on my understanding of inertia, I do not believe this statement is right all of the time...

Heavier car will bounce less using the same spring.

Click to expand...

I think a heavier car may actually be able to overload a suspension (especially if the suspension is set to what a lighter car would use).

That said, once the suspension is all used up, the car has nothing to do but more itself and not suspension components in order to absorb the energy of the car's motion.

Btw, the suspension components, if not fully used, may react to more weight with more reaction.

Also, due to the fact that GT4 is a game, you can't just go and take away complete values like stabilizers and dampers, that could do anything to the game (almost as if there is no control in the experiment).

All that said, I want to see this subject take a solid path towards something meaningful.

If this thread is only here to suggest GT4's visual representation of a car's bounce is "wrong" then there is actually nothing to talk about (in this, the Settings And Tuning Forum).

Btw, have you tried comparing the CPM of heavy cars and light cars at their stock suspension settings?

Also, what exactly is the CPM (cycles of "what" per minute)?

Kent

First off, what in the world is CPM in the game?
Cycle per minute? Cycle what exactly? (this is asked because I honestly don't know )

Click to expand...

This image will describe better






Hz is cycle per second, cpm is cycle per minutes, 1 Hz equal to 60cpm.

Kent

Second, I don't trust your observations based on this single sentence (which also happens to be extremely important to me).

Click to expand...

It seems using "bouncing" term is not correct, this image explain it better.



Wiki also explain this on http://en.wikipedia.org/wiki/Harmonic_oscillator
k is spring stiffness, m is mass, W is "bouncing" frequency.

So you explain by sending me to the wiki of formulas?

I understand the figures shown. 👍

The question is, was your statement "Heavier car will bounce less using the same spring." true?

Did you by chance test the stock settings?

Also and most importantly, the "free vibration" of your examples is not present in GT as there is no way to test GT without the inertia of a car being added to the equation of "how much does the car bounce" and "why could a heavy car bounce more than a light car"?

What I think Suchayo is trying to say is that the spring rate sliding scale indicator is not unit based.
I.E. Soft value 2 for a Civic may be 10 units of hardness while a value of 2 for a Falcon may be 30 units of hardness.
Hard value 12 for civic may be 60 units of hardness while a value of 12 for a Falcon may be 180 units of hardness.

Kent

The question is, was your statement "Heavier car will bounce less using the same spring." true?

Click to expand...

In real life, not in GT2 or GT4.

I am saying GT2 and GT4 spring rate value have to be treat in different way we treat real life spring.

This is why I create this thread. In GT2 heavier car bounce more when using the same spring rate value. I first notice it on BMW 740i vs Lotus Elise. 740i bounce a lot more than elise. I forget about how it is in GT4, never specifically test this.

Kent

Did you by chance test the stock settings?

Click to expand...

Without hacking, we wouldn't know what the spring rate value are in GT4. But as I can see the stock spring rate value in GT2, I don't feel the need to test it. 2.4/2.7 for skyline R32, 1.6/1.8 for subaru 360. Besides, testing how much the car bouncing with 1/1 damper is hard in GT2. IIRC 1/1 damper in GT4 still make some bounce in Subaru 360.

Kent

Also and most importantly, the "free vibration" of your examples is not present in GT as there is no way to test GT without the inertia of a car being added to the equation of "how much does the car bounce" and "why could a heavy car bounce more than a light car"?

Click to expand...

In simple 2 degree of freedom simulation, only car mass (sprung weight), tire mass (unsprung weight), tire springing stiffness, spring stiffness and damper that used in calculation. Momentum and kinetic can be calculated from that too. Although I am not sure wether PD simulated tire springing stiffness in GT4.

2 DOF


1 DOF

Uncle Harry

What I think Suchayo is trying to say is that the spring rate sliding scale indicator is not unit based.
I.E. Soft value 2 for a Civic may be 10 units of hardness while a value of 2 for a Falcon may be 30 units of hardness.
Hard value 12 for civic may be 60 units of hardness while a value of 12 for a Falcon may be 180 units of hardness.

Click to expand...

Yes . You explain it better. I assume car weight is being used to calculate how many unit need to be used, so PD don't have to store the multiplier for each car.

So what are you comparing here or what are you saying?

Why is GT2 even involved?

If all you are saying is "2-20 on the suspension's springs is not lbs." then just come forward now and say "yes" that's what I'm saying.

Kent

So what are you comparing here or what are you saying?
Why is GT2 even involved?

Click to expand...

I only able to test it on GT2, I want to know if GT4 is like this too.

Kent

If all you are saying is "2-20 on the suspension's springs is not lbs." then just come forward now and say "yes" that's what I'm saying.

Click to expand...

Yes in GT2 . Not sure about GT4, this is why I ask.

If PD happen to implement 120-150cpm for the optimal handling, we should use spring rate value between 8 to 14 in GT2 skyline R32.

If we can get the cpm number in GT4, we can test wether PD really implement the optimum spring rate value for handling too. This can change my tuning.

OK a few things I would like to add here.

First to clarify, in the Real World if you take two cars of differing weights, fitted with springs of the same rate then the heavier car will 'bounce' less. However this will only occur if all other factors are removed, such as dampers and anti-roll bars.

The link originaly posted clearly allows this to be seen, it contains a graph that allows you to roughly compare CPM for various sprung corner weights with spring rates.

As an example if you take two cars of differing weights, both fitted with springs rated at 100 lb/in you would get the following results.

Car A - 300 lbs per wheel (Sprung weight) = approx 100cpm = 1.67 hz
Car B - 600 lbs per wheel (Sprung weight) = approx 78cpm = 1.3 hz

So the same spring rate will feel much stiffer on a lighter car than a heavier car.

However I do dispute that this can easily be tested and checked in any of the GT series by simply using visual information.

Claiming that lowering the dampers and anti-roll bar settings is enough is quite simply not true, the article Suchayo used to describe the test says as much. Additionally trying to rely on the visual side of GT is in my opinion not enough.

I fail to see why PD would go to the trouble of assigning values to the spring and then chosing to ignore them? Not a particularly logical thing to do.

For me the test of this is quite straightforward, take two cars in GT4, one roughly half the weight of the other. Set the spring rates the same in both cars and reduce the damper and anti-roll bar setting to min. Drive them and see which one feels harsher over bumps, kurbs and rumble strips.

If its the lighter car then PD got it right, if its the heavier car then PD got it wrong.

Repeat the test for a number of cars to ensure no anomolous results creap in, guess what I will be doing tonight 👍 .


My final point is one I do not make lightly, as it refers to a now closed thread. Sucahyo in the damper thread (and I do agree with Kent this has a wiff of the same thing - opinion stated as fact, visual only testing, etc) you clearly stated that you did not believe that when a cars suspension hit a bump the unsprung mass would move up. Rather you stated in no uncertain terms that when a car hits a bump the sprung mass would be pushed down onto the suspension.

Then you go and post this
and decribe how the unsprung mass is now a factor in suspension movement.

I hope you are aware of what that is showing (and what you are now saying) and how wrong it makes you're previous statements.

Regards

Scaff

Scaff

I fail to see why PD would go to the trouble of assigning values to the spring and then chosing to ignore them? Not a particularly logical thing to do.

Click to expand...

It is better to use natural frequency than actual spring rate unit because:

• it is easier to create the interface, 2.0 for comfort handling, 20.0 for track handling. Using actual spring rate unit would need a different range of value for different car, which can be big number difference. it is more works.
• guessing how the spring rate of unknown or untestable car is easier (guessing extinc car in GT4).
• correcting wrong car weight wouldn't make PD have to reenter spring data.
• from programming perpective, the difficulty is equally the same.

Scaff

For me the test of this is quite straightforward, take two cars in GT4, one roughly half the weight of the other. Set the spring rates the same in both cars and reduce the damper and anti-roll bar setting to min. Drive them and see which one feels harsher over bumps, kurbs and rumble strips.

Click to expand...

the word "reduce the damper", remind me of closed thread .

Scaff

If its the lighter car then PD got it right, if its the heavier car then PD got it wrong.

Click to expand...

I'll wait to this .

Scaff

you clearly stated that you did not believe that when a cars suspension hit a bump the unsprung mass would move up. Rather you stated in no uncertain terms that when a car hits a bump the sprung mass would be pushed down onto the suspension.

Click to expand...

Funny explanation for the first part, wrong impression for the last part.

As the tire move up in rigid body style, it push the supension, suspension will compress because it is pushed by the tire which going up and body which refuse to suddenly move.

After reading some, the natural frequency for unsprung mass is a lot higher than sprung mass. So, every movement receive by unprung mass do not always mimic by sprung mass, it will react, but slower. Unless when unsprung mass is equal to sprung mass, both will fight each other requally.

Scaff

I hope you are aware of what that is showing (and what you are now saying) and how wrong it makes you're previous statements.

Click to expand...

I hope you realised that I believe PD implement SDOF. That is, the tire do not have springiness or dampiness. so the tire would move like a rigid body.
the picture should be this one:




What you explain here is weird:

Scaff

If the damper does not allow the suspension to move quickly then the force will be transfered to the unsprung portion of the car,

Click to expand...

Because from SDOF system picture, the unsprung mass already receive the force, it's up to damper and spring for how much force will be delivered to the sprung mass. Or do you intend to explain a 2 DOF system, where tire have spring and damper value too ? (forget where I put the picture of 2 DOF system with damper, sorry)

sucahyo

it is easier to create the interface, 2.0 for comfort handling, 20.0 for track handling.

Click to expand...

There is (at least) one thing that doesn't support this theory, and that's the spring rates used for different cars. I'll use Scaff's Ginetta G4 as an example here, it has front springs of 6.4 and rear springs of 3.5 which would mean softish springs in the front and virtually road springs in the back.

Also, the fact that heavier cars usually use hard springs and light cars use soft springs clearly points towards the actual stiffness values.

sucahyo

guessing how the spring rate of unknown or untestable car is easier (guessing extinc car in GT4).

Click to expand...

PD had to find the information for the stock car anyway (or maybe they guessed it) and the tuned suspension values have nothing to do with the normal suspension. Thus there is no benefit of using a range as they can enter whatever default values they like.

Just my opinion of course,

- R -

sucahyo

It is better to use natural frequency than actual spring rate unit because:

• it is easier to create the interface, 2.0 for comfort handling, 20.0 for track handling. Using actual spring rate unit would need a different range of value for different car, which can be big number difference. it is more works.
• guessing how the spring rate of unknown or untestable car is easier (guessing extinc car in GT4).
• correcting wrong car weight wouldn't make PD have to reenter spring data.
• from programming perpective, the difficulty is equally the same.

Click to expand...

I quite agree with Greycap here that what you propose here is unlikely, as while what you have said above may well make sense from a programming point of view, it does not from a users point of view.

PD have not used a set of unknown values for spring rates, rather they have used a specific and measurable set of figures. To then not have these represent 'real world' practice would cause huge problems for anyone who knows the real world relationship between spring rates and sprung vehicle weight.

Still I will carry out some tests tonight and get back with the results.

sucahyo

Funny explanation for the first part, wrong impression for the last part.

As the tire move up in rigid body style, it push the supension, suspension will compress because it is pushed by the tire which going up and body which refuse to suddenly move.

After reading some, the natural frequency for unsprung mass is a lot higher than sprung mass. So, every movement receive by unprung mass do not always mimic by sprung mass, it will react, but slower. Unless when unsprung mass is equal to sprung mass, both will fight each other requally.

Click to expand...

I do not want to drag back up everything from the damper thread, but I'm sorry you spend pages and pages in that thread stating quite clearly that I was wrong and even implying that my job was at risk!

You are now saying that I was right and you agreed with me and I just misunderstood it?

I also fail to see what is funny about the first part of my explination and in regard to me having the wrong impression of what you were saying, well I don't think I was the only one. You were quite clear in dismissing any other possibility than yours, which was that upon encountering a bump the sprung mass would depress the suspension.

You said

sucahyo

My opinion:

* spring compressed mainly because car refuse to change direction (to go up), the weight will affect how much force will be generated.

Click to expand...

sucahyo

I hope you realised that I believe PD implement SDOF. That is, the tire do not have springiness or dampiness. so the tire would move like a rigid body.
the picture should be this one:




What you explain here is weird:
https://www.gtplanet.net/forum/showpost.php?p=2241663&postcount=258Because from SDOF system picture, the unsprung mass already receive the force, it's up to damper and spring for how much force will be delivered to the sprung mass. Or do you intend to explain a 2 DOF system, where tire have spring and damper value too ? (forget where I put the picture of 2 DOF system with damper, sorry)

Click to expand...

I agree that it is very unlikely that PD (or for than matter any PS2 sim) will have modeled the natural spring values that tyres exhibit (tyres actually have very little natural damping - that is however something that will vary with the tyre construction and in particular the sidewall).

The information you are now posting is nothing new, this is what I spent weeks explaining in the damper thread and you spent weeks disagreeing with.

In regard to the second part, it was a simple description to just try and get you to understand what you now appear to be clear with. Roughly speaking even with the tyre included in the model the overall effect will be the same.

I always stated quite clearly that force would be transfered to the sprung mass of the vehicle (you disputed this) and that the amount of force transfered would depend on the spring rates and damper settings. With firmer dampers transfering more through to the spung mass (as the unsprung mass is not able to move quickly enough to control it) and resulting in a loss of contact with the road surface.

Of course this is in relation to suspension movement when a bump or surface iirregularity is encountered, suspension movement under load transfer is another thing completely.

I do hope you realise that by now accepting the above it negates a huge part of your argument that lower damper values are stiffer!!!


Regards

Scaff

OK I have put this together as a new post as it's going to be a bit large and a bit technical, so I hope I can get this across clearly.

Spring Rate vs Wheel Rate
OK first I need to get this concept across to start with. In a lot of suspension systems the amount a wheel moves (wheel rate) when it hits a bump does not mean that the spring will compress by the same amount (spring rate).

The suspension acts as a lever and the suspension leverage effect has to be acounted for, as while a wheel may move up by 1 inch from a force of 100 lbs when it hits a bump, this may be translated to a force of 200 lbs and 1/2 inch of movement at the spring. This would be a suspension leverage of 2:1, the problem is unless you can find and measure the exact mounting points for the suspension its hard to calculate the suspension leverage and the relationship between spring rate and wheel rate.

However one type of suspension system always has a leverage ratio of 1:1, and thats the McPherson Strut.



What the hell do we need to know this for?
The reason I need to know the Wheel rate (after all we already have the Spring Rate) is that I can use it to calculate the CPM at each wheel.

The following formula allows us to do this

CPM = 187.8 * √ (A / B)

A = Wheel Rate (lbs/inch)
B = Sprung Weight (lbs)

Now I hope the reason for wanting a 1:1 leverage ratio makes things easier, it allows easy Wheel Rate Calculation, as for a car fitted with McPherson struts all round it will be the same as the Spring Rate.

Now the tricky one is the Sprung weight per corner, I can get the total corner weight per corner without difficulty using the static weight distribution and curb weight. I had to decide what to do and settled on simply using the total corner weight, after all this is more for indicative testing rather that exact testing for real car set-up.

OK so we have the formula and know the requirements of the cars, once these have been selected the values used in GT4 will require conversion.

Curb weight is easy, kgs to lbs if not a problem at at all. However Spring Rate values in GT4 are measured in kgt/mm, the metric norm for spring rates is kg/mm. I must confess this has thrown me since day one and have simply converted the values as if they were kg/mm (into lb/in).


OK so what are the cars
This was fun, trying to find a couple of cars with McPherson struts all round and of differing weights. Sad bloke that I am I knew of one straight off, the original Toyota MR-2, a quick bit of work on the web and I found the second. The Mazda Autozam AZ-1, a stroke of luck as its also has the same drivetrain layout and is a resonable difference in weight.

I fitted both with full racing suspension in GT4, the AZ-1 in question is also one I have previously used and has Stage 3 weight reduction fitted, lowering the weight even more. This should help with the test no end, I also upped the power on the AZ-1 to match the Power to weight ratio of the two cars as much as possiable.



Calculating the Toyota MR2's CPM
Model - Toyota MR2 1600 G-Limited '86

Weight 2,359 lbs
F/R distribution 45.3% / 54.7%
Front corner weight = 534.5 lbs per wheel
Rear corner weight = 645 per wheel

Wheel rate Front = 3.6kg/mm = 41.56 lb/in
Wheel rate Rear = 4.8kg/mm = 55.42 lb/in

Using the above the CPM came out as

Front CPM = 52
Rear CPM = 55



Calculating the AZ-1's CPM
Model - Mazda Autozam's AZ-1

Weight 1,444 lbs
F/R distribution 44% / 66%
Front corner weight = 317.5 lbs per wheel
Rear corner weight = 404.5 per wheel

Wheel rate Front = 3.6kg/mm = 41.56 lb/in
Wheel rate Rear = 4.8kg/mm = 55.42 lb/in

Using the above the CPM came out as

Front CPM = 67.95
Rear CPM = 69.51

The Spring and Wheel rates used were the default values for the MR2, as can be seen the CPM figures for the AZ-1 are higher than the values for the MR2, despite the same spring and wheel rates.

Not a huge surprise as this is how it should be, the real question is how will they feel when we take them for a drive.


Conclusion
OK so using the spring rates above on both cars (and every other suspension setting left at the default) I took the two out for a series of laps around Deep Forest.

The MR2 had a nice fluid ride and did not feel harsh over the rumble strips, the AZ-1 was still a good drive but was clearly the more firm and slightly harsher of the two over the rumble strips.

This would seem to indicate that Spring Rate values in GT4 are as they should be and that as a general rule the same spring rate in different cars will result in a different ride. With the lighter car feeling harsher, just as it should do.

What I hope the above has also done is explained a little more about how car suspension works and how its not a simple case of looking at the spring rates alone to determine the ride. Without all the information to hand, in GT4 at least, we are best off with a trial and error method.

It should also be noted that as the full corner weight was used rather than the sprung corner weight the final CPM values are lower than they should be in all cases.

Regards

Scaff


BTW - Source for all formula was 'Race and Rally Car Source Book' by Allan Staniforth

Greycap

There is (at least) one thing that doesn't support this theory, and that's the spring rates used for different cars. I'll use Scaff's Ginetta G4 as an example here, it has front springs of 6.4 and rear springs of 3.5 which would mean softish springs in the front and virtually road springs in the back.

Click to expand...

Not suggesting they can't use different value.

Scaff

You are now saying that I was right and you agreed with me and I just misunderstood it?

Click to expand...

Nope. I still think you are wrong.

This:
"spring compressed mainly because car refuse to change direction (to go up), the weight will affect how much force will be generated."

is the same as this:
"As the tire move up in rigid body style, it push the supension, suspension will compress because it is pushed by the tire which going up and body which refuse to suddenly move."

is the same as this:


at the moment the wheel impacting the bump, the car body supposed to still have 0 vertical velocity. unless it meets bump before. so with:



the kinetic energy stored in car body (1) would still be 0, speed before and now is the same. so all the power comes from wheel/road (2) goes to the spring and damper. the damper will dissipates the power that goes to it, the spring will stored it. The spring stored the energy by compressing.

For reminder, this is happen just when the tire meet the bump, it is way before it pass over the top of the bump.

relation with how car weight has something to do with this, more weight will make the car lazier to move. Newtons Law number 1:
"Lex I: Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.
"An object at rest or traveling in uniform motion will remain at rest or traveling in uniform motion unless acted upon by a net force.""

Since the velocity still zero it would need more energy to move the car to new vertical speed when the current speed vertical speed is 0. to move from 0 to V would need:



Some image and energy equation from www.me.utexas.edu/~bryant/courses/me344/DownloadFiles/LectureNotes/MechanicalTransl.pdf. others are from wiki.

Scaff

I do hope you realise that by now accepting the above it negates a huge part of your argument that lower damper values are stiffer!!!

Click to expand...

Nope. Still stubborn .

Scaff

Curb weight is easy, kgs to lbs if not a problem at at all. However Spring Rate values in GT4 are measured in kgt/mm, the metric norm for spring rates is kg/mm. I must confess this has thrown me since day one and have simply converted the values as if they were kg/mm (into lb/in).

Click to expand...

In GT2 PAL version has the same number as NTSC 1.2 version but with different unit and give almost the same result.


Subaru 360, no weight mod
NTSC 1.2 version:
2.0/2.0 spring rate = 58cpm
20.0/20.0 spring rate = 106cpm

PAL version:
2.0/2.0 spring rate = 60cpm
20.0/20.0 spring rate = 114cpm


Skyline GT-R R32 '89
NTSC 1.2 version:
2.0/2.0 spring rate = 96cpm
20.0/20.0 spring rate = 160cpm

PAL version:
2.0/2.0 spring rate = 98cpm
20.0/20.0 spring rate = 170cpm


I guess PD learn their mistake.

Scaff

What I hope the above has also done is explained a little more about how car suspension works and how its not a simple case of looking at the spring rates alone to determine the ride. Without all the information to hand, in GT4 at least, we are best off with a trial and error method.

Click to expand...

I see, thanks , it's answered my question 👍.

In GT4 spring rate works like what it supposed to do. I assume a subaru 360 will feels more stiff in 4.0/4.0 spring rate than A skyline R32 or Land Rover Storm.

sucahyo

Nope. I still think you are wrong.

* snip *

Nope. Still stubborn .

Click to expand...

This will be my last piece on the damper topic as that thread was locked, but your arrogance realy does amaze me, you have changed what you said, I was the one who said to you that it was the movement of the unsprung mass that resulted in suspension movement over bumps, you disputed this.

The text and evidence is still in the thread anyone who wants can go and read it and form an opinion of there own.

I'm quite happy for you to go on believing what you will about this subject, feel free to think that cars will suddenly loose contact with the road before they crest a bump (or after they have crested a bump) as the result of rebound; or that "more jump and vibration can be caused by softer damper. Stiffer damper will prevent jumping and vibrating better.".

Me I will just stick to what I do.

sucahyo

In GT2 PAL version has the same number as NTSC 1.2 version but with different unit and give almost the same result.

Click to expand...

I've not even thought about looking at this in GT2, but it would appear that you are just looking at visual information, you know my thoughts on that, its a flawed approach to testing.

sucahyo

I see, thanks , it's answered my question 👍.

In GT4 spring rate works like what it supposed to do. I assume a subaru 360 will feels more stiff in 4.0/4.0 spring rate than A skyline R32 or Land Rover Storm.

Click to expand...

Yes GT4 springs do appear to follow the 'real world' and a comparing a Subaru 360 and R32/Range Stormer with the same spring rate and saying that the 360 will feel much stiffer than the other two is find.

When it gets tricky is if the cars weights are much closer and/or they utalise wildly different suspension layouts.

Regards

Scaff

Scaff

you have changed what you said, I was the one who said to you that it was the movement of the unsprung mass that resulted in suspension movement over bumps, you disputed this.

Click to expand...

, and what make the spring compress then...... something other than unsprung mass pushed the spring and make it compress because the spring being prevented to move up by car body?

whatever you say.

Scaff

I'm quite happy for you to go on believing what you will about this subject, feel free to think that cars will suddenly loose contact with the road before they crest a bump (or after they have crested a bump) as the result of rebound; or that "more jump and vibration can be caused by softer damper. Stiffer damper will prevent jumping and vibrating better.".

Click to expand...

Thanks . I feel relieve know.
and after seeing this graph bellow, I am more stubborn .

x axis is damper ratio, y axis is road holding.

Scaff

I've not even thought about looking at this in GT2, but it would appear that you are just looking at visual information, you know my thoughts on that, its a flawed approach to testing.

Click to expand...

Well, you accused me of lying too when I am guessing how stiff the spring of the car in RBR vs GT4 only by visual cpm observation . I don't think it's flawed. I will keep using this cpm observation when playing other games too.

Scaff

Yes GT4 springs do appear to follow the 'real world' and a comparing a Subaru 360 and R32/Range Stormer with the same spring rate and saying that the 360 will feel much stiffer than the other two is find.

Click to expand...

Ok. I will post again if find something weird.

Scaff

When it gets tricky is if the cars weights are much closer and/or they utalise wildly different suspension layouts.

Click to expand...

What make you so sure GT4 implement many different suspension layout?

sucahyo

, and what make the spring compress then...... something other than unsprung mass pushed the spring and make it compress because the spring being prevented to move up by car body?

Click to expand...

I've never said it did anything other, you are the one who cliamed that when a car encoutered a bump the force of the car body pushed down compressing the spring. You used that point as the crux of your argument that the force generated by the car body traveling downwards would rebound with sufficent force to cause the car to loose contact with the road before it crossed th top of the bump.

sucahyo

Thanks . I feel relieve know.
and after seeing this graph bellow, I am more stubborn .

Click to expand...

Great graph!!! With no context at all its totally meaningless.

Also we are supposed to take that graph as proof of what, how does this change you statement that stiffer dampers reduce loss of conatct with the track (jumping) or harsh vibrations? I mean I have posted countless quotes and references from damper manufacturers and acknowledged experts all of which say you are wrong, and you give us a graph!!!!

sucahyo

Well, you accused me of lying too when I am guessing how stiff the spring of the car in RBR vs GT4 only by visual cpm observation . I don't think it's flawed. I will keep using this cpm observation when playing other games too.

Click to expand...

You can't use visual wheel movement to 'guess' CPM when the dampers and Anti-roll bars are still in the system, for crying out load the article you posted at the start of this thread quite clearly says that you need to remove both the dampers and Anti-roll bars to get acturate results.

I mean logic tells you this, dampers do just as the name suggests, they damp the spring therefore they are going to have a profound effect on the visual information. And Anti-rolls bars are a form of spring that acts under laterial roll, as they are firmly fixed to the suspension if any laterial forces are acting on the car they will most certainly effect the result.

You still want to maintain that its not a flawed approach?

I did not say you were lying I said you were wrong. Additionally I never even asked you to look at spring rates in the first place on the RBR videos.

sucahyo

What make you so sure GT4 implement many different suspension layout?

Click to expand...

Early testing on a couple of cars has raised a few questions and I want to finish testing this first, I'm not 100% sure which is why I said there was a need to be careful. Anyway this should form the basis for starting settings only, driving the car at the track you are tuning for is the only way to know what the right rate for a driver is.


Regards

Scaff

Scaff, refuse to go up do not mean it push down.

When I said this:
"spring will force the car to go up by its springing power and store the force it receive while compressing, car weight will resist this until the car move the same speed as bump vertical."

I assume you know that the unsprung mass is following the bump uphill countour.


For the graph, I don't intend to proof anything, it's just a FYI that I am happy I found someone has proof that under damping has less road holding than stiff damper, both hold less than optimal value. if you curious, read this www.engr.uvic.ca/~fsae/Car/car2005-Damping.htm. If you think they are wrong or I am the one who understand it wrong, both is ok. But don't expect me to believe that GT2 and GT4 do not have damper tuning reversed.

For cpm analysis, sure damper make it harder to analyze, but since many games tend to allow the car to bounce few time, it's enough for me to guess. Guessing how stiff the damper in your GT4 video is a lot harder than this. For anti roll bar, I assume the worst effect is make the left and right wheel bounce synchronously.

For RBR spring, I can help thinking how soft RBR stiff spring are compare to GT4 at the first sight.

Ok for suspension layout. Thanks .

^^What is you native tongue? It might be a good idea to translate that guide to your own language. Use a web based translator of some sort.

sucahyo

Scaff, refuse to go up do not mean it push down.

When I said this:
"spring will force the car to go up by its springing power and store the force it receive while compressing, car weight will resist this until the car move the same speed as bump vertical."

I assume you know that the unsprung mass is following the bump uphill countour.

Click to expand...

You assume I know that; oh very well done. What the hell do you think I have been saying for the last month?

This sounds a lot like you have recently come across that reference and realise that you have been working with a flawed set of assumptions (guess what I said that) and are now furiously back-pedaling.

I would agree with Team666 that you also do not appear to have fully read and/or understood all of that piece, as firstly it discounts so many of your firmly held theories, particulalrly the one regarding higher damper values reducing vibration and harshness.

Secondly the articels conclusion states that this is simply a starting point looking at limited information and that still the best way i sto use this as a start point and on track testing is the best way to finalise settings.

sucahyo

For the graph, I don't intend to proof anything, it's just a FYI that I am happy I found someone has proof that under damping has less road holding than stiff damper, both hold less than optimal value. if you curious, read this www.engr.uvic.ca/~fsae/Car/car2005-Damping.htm. If you think they are wrong or I am the one who understand it wrong, both is ok. But don't expect me to believe that GT2 and GT4 do not have damper tuning reversed.

Click to expand...

The article does not claim to prove anything, quite the opposite, nor does it claim to prove that underdamping is less stable than overdamping under every situation.

The article itself is not bad, a lot of it is taken from a source I use myself (Allan Staniforth), but it is limited in that it covers a single vehicle and states this quite clearly.

You also seem to forget that I have never claimed that underdamping could result in a loss of contact with the surface, rather it was you that disputed that over damping would result in a loss of contact (opps you have just proved yourself wrong).

In regard to your opinion on GT2 and GT4, what you believe is up to you, however do not be surprised if I continue to dispute it.

sucahyo

For cpm analysis, sure damper make it harder to analyze, but since many games tend to allow the car to bounce few time, it's enough for me to guess. Guessing how stiff the damper in your GT4 video is a lot harder than this. For anti roll bar, I assume the worst effect is make the left and right wheel bounce synchronously.

Click to expand...

Dampers do not make it harder to analyis, they make it impossiabel to accuratly analyis, your own reference on the subject says so. Additionally Anti-roll bars will have a lot more of an effect that you assume, they effectively act as springs during lateral load transfer.

Simply put you can't get accurate results just by looking at the car with the damper and ARBs still in place, and thats assuming that the visual information in both is accurate enough in the first place.

sucahyo

Ok for suspension layout. Thanks .

Click to expand...

No problem


Regards

Scaff

@Team666, translator can make it harder to understand.


@Scaff, I write it after posting this.
explaining how the tire follow the road bump, but jump before it reach the top.

The flaw in my explanation when I see it now is the use of car momentum, when I should use car kinetic.

The thread got closed before I complete my half done explanation. No explanation what happen after passing the top of the bump, or what happen when the tire pass the top of the bump when suspension in compression state.

Do we have to continue damper conversation here? If not please stop questioning about it.

We have different opinion. Why do I have to proof it again?


If you want to talk about damper why not investigating why all GT store single damper value on two places. Do it really for low speed and high speed damper value, so whenever PD feels ready, it can be turned on right away?


For visual analysis, even a rough guess can be helpfull. So, even when damper and stabilizer making judgement harder, it still can be done. In a game that allow it, I do my tuning 30% visual.


BTW, what is your testing method for proofing wether GT4 implement various suspension layout or not?

sucahyo

BTW, what is your testing method for proofing wether GT4 implement various suspension layout or not?

Click to expand...

In regard to the damper thread I will send you a PM on that subject.

As far as the suspension layouts go, I'm not even ready to say yet if differences have been implemented is as far as effecting spring rate vs wheel rate.

Still working on the tests, etc. Its going to be a difficult one.

Regards

Scaff

ok.

Here we go again......