clarify damper comp/ext

[Schadenfreude13]

Wow, explinations are flying like glitter at a Kesha concert. Lol.

Ok, one more try:
Springs are there to support the weight of the car. The spring strength/rate is proportional to the weight.
Dampers are there to counter the coil/recoil of the weight on the springs and are proportional to the spring strength/rate.
Roll bars counter lateral body roll.

So if I use Anti-roll bars to counter lateral roll, which counter longitudal roll? Dampers or springs? What I'm hearing is: Dampers mostly.

Actually, the more correct statement is that springs and dampers counter longitudinal roll, as the two always work in conjunction with each other...

 

[esoxhntr]

race cars are set up with a frequency around 2.2 any higher is considered too stiff.

After dropping the weight and lowering the ride height I calculate the frequency of the springs to insure I get them stiff but not overdone or simply put too stiff.

How do you calculate this? Or is it proprietary?

 

[Ronald6]

Actually, the more correct statement is that springs and dampers counter longitudinal roll, as the two always work in conjunction with each other...

So which is correct:

Springs with alot of weight, and therefore strengthened, need stronger dampers when compared to springs with less weight and therefore weaker.
Or
Springs with alot of weight, and therefore strengthened, don't need any to be stronger than weaker springs with less weight.

Budious suggests the second.

 

[GrimSinn]

Yellow Bird is rear engine and rear heavy. The stiffer springer supports a higher proportion of the car's weight distribution and receives less from the front the lighter front under acceleration. According to frequency though if the spring rates are in harmony, then applying the same damper strength to cancel out oscillation creates the same momentum change rate. Lighter spring handles less weight at same rate as heavier spring handles more weight with same dampers as I understand it, this is why I think having extension set front to rear at the same rate does yield better results if you have the proportion of the front to rear setup correctly.

I think you may be overlooking that the front and rear springs are holding different weight (in a car thats not 50/50) and the spring rates bringing them to a equal frequency will not be the same. We are trying to ballance the suspention but use different settings to do so baised on where the weight is.

 

[GrimSinn]

How do you calculate this? Or is it proprietary?

I use the formula for spring frequincies however there are some X values I use estimations/averages for, stil working out the calculations, but it's coming along nicely.

 

[Schadenfreude13]

So which is correct:

Springs with alot of weight, and therefore strengthened, need stronger dampers when compared to springs with less weight and therefore weaker.
Or
Springs with alot of weight, and therefore strengthened, don't need any to be stronger than weaker springs with less weight.

Budious suggests the second.

I go with the first, sort of, it's a bit more complicated than the way you worded it, or in fact, the way I worded it. I was just trying to present a very basic model of what it is dampers do. Also, I base that on what I've read in automotive manuals, like the Bosch Handbook, for example, and I believe Budious' notion of how dampers work are based mostly on his experience with tuning in the GT series, which is far from a perfect model of reality.

Edit: On second thought, some of what Budious is suggesting makes a bit of sense to me. This assumes we're talking about a car with a low ride height and VERY stiff springs. Since the springs compress much less, the sort of oscillating recoil effect that dampers, well, dampen, is less pronounced so the dampers no longer have to be as strong. In other words, if we imagine a graph with the x-axis representing the spring rate and the y-axis representing damper rate, then the resulting plot would be bell curve, rather than a rising slope...

Edit #2: I re-read Budious's post. He's referring to compression damping, not extension damping (I told you this gets complicated). The sources I've read regarding setup of racing suspensions does mention the need to have equal front-to-back (and often light) compression damping (assuming that springs and roll-bars are set up correctly for the car's weight distribution and resulted in a neutral car). Forget about how my first edit is supposed to relate to Budious's post. I left it up there, as the stuff about the graph is quite relative to extension damping...

 

[budious]

Also, I base that on what I've read in automotive manuals, like the Bosch Handbook, for example, and I believe Budious' notion of how dampers work are based mostly on his experience with tuning in the GT series, which is far from a perfect model of reality.

If you want real car tuning advice, goto a car tuning forum; I just speak from the point of view of what works in the game. Sometimes, I base those assumptions on actual principals, in their full form or simplified, at other times I pull them out of my ass. Look at the tuning competition thread and see how many cars have similar extension damper settings and the results posted, drive them for yourself. Not everyone may know why they keep extension even front to rear but most have learned it nets good results.

I think you may be overlooking that the front and rear springs are holding different weight (in a car thats not 50/50) and the spring rates bringing them to a equal frequency will not be the same. We are trying to ballance the suspention but use different settings to do so baised on where the weight is.

If the front supports 5.5KG per mm of compression, and the rear supports 6.4KG per mm of compression, and the ratio of weight setting of those springs is near 55:64 when stationary then the load and unload rate should be uniform with the same dampening applied. If the ratio was not 55:64 then you could adjust dampers but that would net as many gains as retuning the front to rear spring proportions.

As for motion ratio, I did make my Supra over 1.5" faster over the stock setup on Autumn Ring Mini using what I think is an accurate way to calculate motion ratio and new weight distribution figures. The funny thing, once I achieved this, my times were almost identical with all dampers set at equivalent values in 1-4 range with anti-roll at 1; meaning they moved together perfectly until damper oscillation cancellation reached such a rate as to limit their ability to effectively absorb bumps and maintain traction.

The bad news is, I was wrong about being able to base those figures off of any figures sourced in the game. I think some bit of Google research will be involved with each car.

 

[Schadenfreude13]

If you want real car tuning advice, goto a car tuning forum; I just speak from the point of view of what works in the game. Sometimes, I base those assumptions on actual principals, in their full form or simplified, at other times I pull them out of my ass. Look at the tuning competition thread and see how many cars have similar extension damper settings and the results posted, drive them for yourself. Not everyone may know why they keep extension even front to rear but most have learned it nets good results.

I just edited the post you quoted, so no need to repeat myself here, but basically /agree, as I remembered a couple more things I've learned from real-world sources after posting...

 

[Ronald6]

Ok, got all of that. Now onto a different question. This one is about body roll.

Here is the thought model:
A car with a 50/50 weight distribution will also have equal springs and dampers (at least in this basic thought model). Left/right (lateral) and front/back (longitudal) the car will pivot on the center of the car.
Now take a car with a 30/70 weight distribution (to stick with my Yellowbird examples). The back springs will be much stronger than the front. Lest say the dampers are all at 5 for this example for simplicity.
If I'm driving down a streight stretch of road and I start to swerve back and forth. In the 50/50 car the front and back will sway equally, at the same frequency.

Here's the question: in the 30/70 car will the front and back sway equally? Is this frequency based on the spring frequancy?

I'm unsure if a strong spring with a heavy weight has the same frequency as a weak spring with a light, but proportional, weight.

Another question: instead of swerving I'm breaking and accelerating. In a 50/50 car the pivot point will be equal between the wheels.
In a 30/70 car will the pivot point still be in the middle.
When you stiffen the dampers to adjust the handling (countering under- and oversteer) does this shift this pivot point?

 

[Schadenfreude13]

Ok, got all of that. Now onto a different question. This one is about body roll.

Here is the thought model:
A car with a 50/50 weight distribution will also have equal springs and dampers (at least in this basic thought model). Left/right (lateral) and front/back (longitudal) the car will pivot on the center of the car.
Now take a car with a 30/70 weight distribution (to stick with my Yellowbird examples). The back springs will be much stronger than the front. Lest say the dampers are all at 5 for this example for simplicity.
If I'm driving down a streight stretch of road and I start to swerve back and forth. In the 50/50 car the front and back will sway equally, at the same frequency.

Here's the question: in the 30/70 car will the front and back sway equally? Is this frequency based on the spring frequancy?

I'm unsure if a strong spring with a heavy weight has the same frequency as a weak spring with a light, but proportional, weight.

Another question: instead of swerving I'm breaking and accelerating. In a 50/50 car the pivot point will be equal between the wheels.
In a 30/70 car will the pivot point still be in the middle.
When you stiffen the dampers to adjust the handling (countering under- and oversteer) does this shift this pivot point?

The answer to your first question is yes, in theory. By increasing the stiffness at the heavier part of the car you've made it behave like the weight is more evenly distributed.

I'm not sure about number two at the moment. I'd have to reflect a bit on that one.

Edit: On number two, what you refer to as the 'pivot point' would be the center of gravity. Assuming a perfect weight distribution (50/50 when it comes to automotives isn't always perfect, but pretty damn close) your center of gravity will be dead center of the car. In the 30/70 car, the center of gravity will be towards the rear, even when the suspension is stiffer in the rear, because you haven't actually re-distributed the weight (at rest). To answer your question, your center of gravity is never going to move based on the suspension alone, and to make things more complicated, you have to remember it (the center of gravity) shifts around as the car accelerates, declerates, and corners. So I guess the best answer I can come up with is that a stiffer suspension means less shifting of the center of gravity, therefore the car will feel more nuetral under destabilising conditions... I feel like that's hardly an answer at all but the best I can come up with...

 

[budious]

To answer your question, your center of gravity is never going to move based on the suspension alone, and to make things more complicated, you have to remember it (the center of gravity) shifts around as the car accelerates, declerates, and corners. So I guess the best answer I can come up with is that a stiffer suspension means less shifting of the center of gravity, therefore the car will feel more nuetral under destabilising conditions... I feel like that's hardly an answer at all but the best I can come up with...

You also have to account for how hamburgers Bob ate for lunch, how much crap he piled in the trunk, and did he have enough to fill the tank at last gas up.

Also, I rarely see on actual automotive forums, where people actually balance spring rates on weight distribution. There tends to be a greater focus on handling and transfer forces, and many stock cars even when motion ratio is taken into account, do not have springs balanced for their weight distribution. GTs stock settings mirror this manufacturer inaccuracy, I italicize it because it's really not, but I think GTs physics engine is much more generous in benefits of pairing weight distribution to spring rate than would be the results from performing such an exercise in the real world. I'm not an expert, of course, but that has been my impression from the real discussions I have read through on numerous cars.

 

[Schadenfreude13]

There tends to be a greater focus on handling and transfer forces, and many stock cars even when motion ratio is taken into account, do not have springs balanced for their weight distribution.

That's exactly what I was trying to get across in my crappy, stream-of-consciousness sort of way. Spring balance is about weight transfer, not weight distribution. Good way to sum it up...

 

[GrimSinn]

When you shift weight wether it's going to the front or rear it's the same amount. However since the weight on the front is not the same as the rear the weight under load is different.

For example a car with 1580kg of weight and a 67/32 weight split is supporting 1072kg on the front springs and 507.86 on the rear. While braking at 1g the car shifts 395 pounds forward while accelerating 1g it shifts 395 to the rear.

Soooo the front is dealing with 1467kg under load while the rear is managing 902kg under load. I use more dampening (higher comp setting in the front then the rear because even though the spring frequency is the same front/rear (using different spring rates) they are managing different weight under load.

I need stronger resistance to compression dealing with 1467kg then I do for 902kg.

 

[Ronald6]

^^ Thank you. Didn't know the weight was the same. That's assuming the same amount of Gs, right?

So... when you strengthen the front what you're doing is delaying the weight that will be shifted under decceleration?

With a weight distribution of 50/50 and stronger springs in the front the same amount if weight will be shifted but the shift will be slower under decel and faster under accel. Is this right?

(Best thread ever.)

 

[GrimSinn]

^^ Thank you. Didn't know the weight was the same. That's assuming the same amount of Gs, right?

So... when you strengthen the front what you're doing is delaying the weight that will be shifted under decceleration?

With a weight distribution of 50/50 and stronger springs in the front the same amount if weight will be shifted but the shift will be slower under decel and faster under accel. Is this right?

(Best thread ever.)

To put it simple...

Right

Right

&

Right (except for me I would most likely have the springs even for a 50/50 split while my stiff comp setting on my dampeners reduces the rate of forward weight transfer.) however some like to use the springs to reduce body roll, I prefer a balanced spring using dampeners to reduce body roll.


We are manipulating the rate (or speed if you want) of weight transfer while the amount transferred stays the same.

For me it's about making the weight transfer smoother, less sudden (or less "shocking" lol ) thats just how I do it though.

One of the reasons I tune the frequency of my springs is because I already know that a frequency over 2.2 is considered too stiff. It's important to have your spring stiff enough to support the weight it will be required to yet not so stiff it cancels out the whole reason for the springs to begin with. If the spring is too hard it literally becomes useless.

 

[budious]

...

I need stronger resistance to compression dealing with 1467kg then I do for 902kg.

Good points.

Here is the formula I have been working on for taking motion ratios into account, though knowing the actual motion ratios to use is kind of an arbitrary exercise at the moment. I did recall reading that one of shocks was mounted mid-arm on the Supra so I just assumed a motion ratio of 2:1 for a simple exercise.

I need to test this formula in principal across a wider base of test cars, so offer feedback with data sets you try including weight distribution and motion ratio resources you find online for the cars you attempt to apply it to.

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Long Method (required for adjusting frequency, to maintain stock frequency use Shortcut Method)

Toyota Supra 3.0GT Turbo A '88 - resources indicated a 53/47 weight distribution, so lets attempt to find our base spring rates before applying additional rate for transfer loads.

FR WT DIST = (SR FR / FR MR) / ((SR FR / RR MR) + (SR RR / RR MR))

RR WT DIST = (SR RR / FR MR) / ((SR FR / FR MR) + (SR RR / RR MR))

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If you got a graphing calculator: (X = FR SR; when RR SR = 6.4)

Y = (X / 2) / ((X / 2) + (6.4 / 1)

Set your window on the graph so Min X: 0; Max X: 20; Min Y: 0; Max Y: 1

You can now use the trace function to follow the curve, where Y=.530 then X=14.46

So approximating for now, but we'll round off to 14.3 or 14.4 for Front Spring Rate if Rear Spring Rate is 6.4 for the Supra. I used 14.3/6.4 in my testing and found these rates to be approximately 1-1.5" faster on Autumn Ring Mini than the stock rates in the fully customized suspension depending on the dampers used. Either this is a fluke result which is why it needs more testing, or I'm on the right track. Though we could take this to the next step and add in GrimSinn's weight transfer figures to the spring rate calculations and see if that improves our results further.

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Deep Forest Raceway
299HP Supra w/ Low RPM Turbo, Sport Softs, FC Suspension; everything else stock.

Stock FC Suspension
RH: 0 / 0
SR: 13.5 / 6.8
Ext: 5 / 5
Com: 5 / 5
ARB: 3 / 3
Cam: 0.0 / 0.0
Toe: 0.00 / 0.00 (zeroed for testing)

Alternative Setup A for RR SR = 6.4
RH: 0 / 0
SR: 14.3 / 6.4
Ext: 5 / 5
Com: 5 / 5
ARB: 3 / 3
Cam: 0.0 / 0.0
Toe: 0.00 / 0.00

Alternative Setup B for RR SR = 6.8:
RH: 0 / 0
SR: 15.3 / 6.8
Ext: 5 / 5
Com: 5 / 5
ARB: 3 / 3
Cam: 0.0 / 0.0
Toe: 0.00 / 0.00

----------------------------------

Best Lap Results (based on short 5 lap run);
Stock: 1:25.7" (least consistent lap times)
Alternative A: 1.25.5" (more consistent lap times)
Alternative B: 1.25.0" (noticeably stiffer but produced best lap)

----------------------------------

Shortcut Method (and original frequency):

FR SR = 2(FC SUS DEFAULT FR SR x WT DIST FR)
RR SR = 2(FC SUS DEFAULT RR SR x WT DIST RR)

14.31 = 2(13.5 x .53)
6.392 = 2(6.8 x .47)

What this does also is keep the original frequency ratio. You notice 0.4KGf/mm were removed to the rear and 0.8KGf/mm (motion ratio of 2.0) was added to the front. Simple, yes?

Actually, now that I have thought about this a little more, it could be the perfect test for determining motion ratio of front to rear travel if you know twice as many units removed are added elsewhere. Then again, I haven't ruled out this was coincidental. More test cases need to be made.

----------------------------------

 

[GrimSinn]

Believe it or not I was at work all day, then Mechanics school all night (I'm burnt) I'll look over your math (slowly) but what I do is get my wheel rate so I can get my spring frequency. To get my Wheel Rate I divide my spring rate by my motion rate multiplied by itself then multiplied by the angle correction factor.

WR = SR/((MR*MR)*ACF)

Then I use the formula to get the frequency

187.8*SQRT(WR/Sprung Weight)/60

Then I adjust the spring rate until I get a frequency around 2.2 and move on to my Weight transfer / Lateral Weight Transfer calculations for dampeners/sway bar tuning.

 

[budious]

Interesting... that's a lot to compute. Lot more figures on each car than I want to try to find in Google also, lol.

Updating prior post with a shortcut method.

You know, I'm about ready to call it quits on this game. I can't make heads or tails out of the Integra Type R. Didn't matter what spring rates I put in there, it ran just about the same lap times around Autumn Ring Mini. After I wanted to try an extreme test case (15.0 F / 3.0 R) of max front to min rear and ended up beating my previous best lap by half a second I decided to call it a night...

 

[GrimSinn]

There Are a few things to always keep in mind.

First thing is that the most important thing is how it handles to you. If a car is balanced to produce the most grip in corners, yet twitchy and too difficult to control to you, it's most probably not going to be as consistently fast as the same car that is not as grippy in the corner yet easier for you to control.

Next when adjusting the Dampeners in GT we are ONLy adjusting the low speed dampening and not the high-speed dampening. High-speed dampening refers to the dampeners reacting to bumps where low speed reacts to weight shifting. Keep in mid the low speed adjustment do still effect the high speed dampening however the impacts are far from as pronounced.

Low comp/high exp setting on the same dampener vs high comp/low exp on the same dampener. What is right? Both. It's all a matter of how the car handles to your style. From what I've researched low comp/high exp is used where there will be high levels of downforce (aero kits, wings, high body generated downforce) where high comp/ low exp seems used when there is a lower downforce factor.

Either way what feels best to your style is right.

 

[budious]

Low comp/high exp setting on the same dampener vs high comp/low exp on the same dampener. What is right? Both. It's all a matter of how the car handles to your style. From what I've researched low comp/high exp is used where there will be high levels of downforce (aero kits, wings, high body generated downforce) where high comp/ low exp seems used when there is a lower downforce factor.
.

Right, I've kind of noticed the same things. Ext > Com also tends to do better on courses with cambered corners for cars without downforce as well. However, going to tracks like Suzuka, Fuji, Tsukuba where most of the cornering is flat, Ext = Com tends to work better.

As for the conditions you listed. Low compression is slow compression which is a higher value and high expansion is fast expansion which is a lower value (Com > Ext). High compression is fast compression which is higher value than low expansion which is slow expansion which is a higher value (Ext > Com). What you say is true but we're always arguing about polarity around here.

 

[Trevlac217]

FR WT DIST = (SR FR / FR MR) / ((SR FR / RR MR) + (SR RR / RR MR))

RR WT DIST = (SR RR / FR MR) / ((SR FR / FR MR) + (SR RR / RR MR))

----------------------------------

Would you clarify the items used in this formula, please?

 

[xXmysterio32Xx]

Just wanna see if I have this all straight
Front Compression:
Soft = raised rear, low front under brakes = oversteer on corner entry.
Hard = low rear, raised front under brakes = understeer on corner entry.

Rear compression:
Soft = low rear, raised front under accel = understeer on corner exit.
Hard = raised rear, low front under accel = oversteer on corner exit.

Extension settings imply how long it would take the dampers to return to their 'extended' state after compression. Low extension rate = faster rebound = lower effect after compression. High extension rate = slower rebound = longer effect after compression.

 

[JackWilson]

higher compression values = more difficult to compress the shock
lower compression values = easier to compress the shock

higher extension values = more difficult to extended the shock
lower extension values = easier to extend the shock

You got it spot on there mate. 👍