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Rank: A-Class Racing License
#26 Posted : Friday, December 6, 2019 10:22:17 AM(UTC)
Thats great and all but it comes up with numbers similar to stock. May be correct for irl, but its not going to make a good tune for forza physics. Its too middle of the road and not at the extreme enough for bump or rebound. Most of my setups have always been around 9-11 rebound and 1-3 for bump.

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#27 Posted : Friday, December 6, 2019 12:08:38 PM(UTC)
Originally Posted by: PTG Baby Cow Go to Quoted Post
Thats great and all but it comes up with numbers similar to stock. May be correct for irl, but its not going to make a good tune for forza physics. Its too middle of the road and not at the extreme enough for bump or rebound. Most of my setups have always been around 9-11 rebound and 1-3 for bump.



You're missing the point. The numbers the damping calc put out inside the game would be what you would assume to be critical damping. You would then tune to the % of critical you want. You actually do not want a ton of damping, you also want as little spring as possible too.

http://farnorthracing.com/autocross_secrets19.html
Rank: A-Class Racing License
#28 Posted : Friday, December 6, 2019 12:41:44 PM(UTC)
And once again in one of these damping threads. I dont care what rl theories and practices say thats just not as good or fast in forza. Tune to the game, this game is way too far off to be tuning to real life perameters. Min/max or max/min works quite well in forza in most situation and is better than mid tier numbers. Do with that what you will, but with the limited information this game gives you are still using arbitrary numbers to come up with even more arbitrary numbers.

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#29 Posted : Friday, December 6, 2019 1:11:47 PM(UTC)
Originally Posted by: PTG Baby Cow Go to Quoted Post
And once again in one of these damping threads. I dont care what rl theories and practices say thats just not as good or fast in forza. Tune to the game, this game is way too far off to be tuning to real life perameters. Min/max or max/min works quite well in forza in most situation and is better than mid tier numbers. Do with that what you will, but with the limited information this game gives you are still using arbitrary numbers to come up with even more arbitrary numbers.


True, there is Pcars or iRacing if I want to get into the gritty details and feel good about a IRL setup.

It's still a fun exercise to compare the real world to Forza IMO.
Rank: B-Class Racing License
#30 Posted : Wednesday, December 11, 2019 11:19:04 AM(UTC)
Originally Posted by: xShatterPointsx Go to Quoted Post
I'm happy I found this thread. I have been trying to conceptualize the units for damping in FM7. It's impossible to figure what number = critical damping as the weight of each car changes and there is no unit of weight assigned to the damping adjustments. So I have been using the damping as a 1-10 = 100% or 10 would be critical damping. It seems to work.


With stock weight distribution, entering the weight, distribution, and initial spring settings of an installed adjustable suspension, and the correct average damping/bump ratio in the calculator, the calculator's numbers match the initial damper settings. Ergo, the relativity of the initial settings indicates that the damper tuning parameter is coefficient, not ratio.

Edited by user Wednesday, December 11, 2019 11:23:05 AM(UTC)  | Reason: Not specified

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#31 Posted : Wednesday, December 11, 2019 1:50:48 PM(UTC)
Originally Posted by: NumberlessMath Go to Quoted Post
Originally Posted by: xShatterPointsx Go to Quoted Post
I'm happy I found this thread. I have been trying to conceptualize the units for damping in FM7. It's impossible to figure what number = critical damping as the weight of each car changes and there is no unit of weight assigned to the damping adjustments. So I have been using the damping as a 1-10 = 100% or 10 would be critical damping. It seems to work.


With stock weight distribution, entering the weight, distribution, and initial spring settings of an installed adjustable suspension, and the correct average damping/bump ratio in the calculator, the calculator's numbers match the initial damper settings. Ergo, the relativity of the initial settings indicates that the damper tuning parameter is coefficient, not ratio.



You need to know the ratio in order to derive the coefficient. Also we do not have the velocity of the damper at a given moment in time. Based on the singular nature of the adjustment it is a linear system and does not offer a digressive setup such as PCars.
Rank: B-Class Racing License
#32 Posted : Thursday, December 12, 2019 5:22:21 PM(UTC)
Neither ratio nor coefficient are necessary to create a table of equal-ratio front-rear damper coefficient value pairs. It's probably possible to generate velocity/time traces for each wheel using data out. Yes, it appears they are linear without adjustment.
Rank: D-Class Racing License
#33 Posted : Sunday, December 29, 2019 1:16:14 AM(UTC)
I have been struggling with the math of Ride frequency calculations all morning in FH4 and just stumbled onto this thread.

Using https://www.youtube.com/watch?v=_A1Q3lkn0i0 as my first reference.

Mike has the Spring Rate as k = (2πf)²w / 2g
where f is the frequency, w is the corner weight (with down force), and g is gravity (32 in imperial units). This produces sensible looking answers in imperial if you just assume the final units are in lb/in, but I don't know why gravity is in there.

Khan Academy was my next stop for a high school refresher.
Ah yes - the period of an mass driven oscilating spring is given by: T=2π√m/k
So we can turn that around and solve for k:

k = 4mπ²f²
where the mass is in kg, and would be the corner (sprung mass) of the car, f is the frequency, and k will be the spring rate in Nm⁻¹ or equivalent english units.
The display units in Forza are Kgf/mm, so /9807 to convert. Which gives stupidly small results.

https://eibach.com/us/p-...uspension-worksheet.html was next.
They seen to just ignore the 2 pi, and throw in a strange constant: 187.8. whatis that? Investigation reveals its √G*60. Only problem is: thats metric G, not english G, which means, OMG the guys over at Speed Academy - that Blog that we both found and referenced - just tuned a RL vehicle with maths that was out by a factor of ~2. Oops.

Then theres Dr Tuned: https://www.drtuned.com/...s-suspension-frequencies
Now here are some proper physics looking formulas, on a racing site. No dodgy constants thrown in. A calculator. Tables of expected frequencies. But applying these calculations to Forza produces cars with stupid / out of band frequencies.

Its at this point I am leaning strongly to the idea that frequency analysis of the tlemetry stream is the only way to determine if the spring values in ForzaX are in fact at all meaningful at all.

Edited by user Sunday, December 29, 2019 1:21:12 AM(UTC)  | Reason: Not specified

Rank: D-Class Racing License
#34 Posted : Sunday, December 29, 2019 4:50:17 AM(UTC)
OMG!
Ive been working in metric units. And I don't know if this is FH4, or FM7 or the entire series, but, the car I am looking at as a set of springs that when I look at their min and max are: 277.2lb/in and 1386/2lb/in in English units, and when I switch to my default (English), the same min and max are: 49.5 kgf/mm and 247.5kgf/mm.

But, if I google the conversion ratio: 0.0178579673 ... then FH4 should be displaying 4.94 kgf/mm and 24.75kgf/mm. Which is where my spring calculations kept on landing me, making me think I'd missed a conversion from Newtons to kgf (why oh why does motor sport still use kgf!?) and/or generally mistrust the source of the equations.

Its been a Forza display issue all along. With a factor of 10 change to my spring rates, my frequencies are probably going to end up in range. But smudge it. I'm going to play. Enough time wasted on this for one weekend.
Rank: B-Class Racing License
#35 Posted : Friday, January 3, 2020 7:40:40 PM(UTC)
The conversion between kn/m and kgf is less than 2% difference iirc. Every other game I've tuned in uses newtons or kn/m, agree it's strange Forza chose kgf.
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#36 Posted : Sunday, January 5, 2020 1:10:57 AM(UTC)
It is heartening to see others interested in the subject of using using using math and science to assist with tuning.

I have some questions as I come from an entirely FH4 background,

I made optional fields in my spreadsheet take the min and max values from the ring rates so it calculates and displays the min and max frequencies available to select in the car you are trying to tune.
I chose cpm rather than Hz as it seems more of a standard in motorsports, and the numbers are more usable (30 and 60 vs .5 and 1 etc).

Display units aside, when I enter the mass and min, max spring rates available to cars like the Mosler in FH4, I get a tiny range of Hz values: 2.5 to 4 - All crazy high.
Rank: C-Class Racing License
#37 Posted : Sunday, January 5, 2020 5:32:59 AM(UTC)
Originally Posted by: GreenZombie76 Go to Quoted Post
Display units aside, when I enter the mass and min, max spring rates available to cars like the Mosler in FH4, I get a tiny range of Hz values: 2.5 to 4 - All crazy high.

I don't think we can directly compare real-world frequencies with in-game frequencies, at least in FM7. Up the thread a bit NumberlessMath and I got into a discussion about the discrepancy. I personally don't worry about it; I just use the calculator to jigger the numbers around until the car drives the way I want it to, and whatever that puts the frequencies at is whatever it puts the frequencies at. The calculated frequency just gives me a nice, easy-to-remember number to quantify how much adjustment I want to make while tuning.
Rank: D-Class Racing License
#38 Posted : Sunday, January 5, 2020 9:04:36 AM(UTC)
Originally Posted by: Mr Pinstripes Go to Quoted Post
Originally Posted by: GreenZombie76 Go to Quoted Post
Display units aside, when I enter the mass and min, max spring rates available to cars like the Mosler in FH4, I get a tiny range of Hz values: 2.5 to 4 - All crazy high.

I don't think we can directly compare real-world frequencies with in-game frequencies, at least in FM7. Up the thread a bit NumberlessMath and I got into a discussion about the discrepancy. I personally don't worry about it; I just use the calculator to jigger the numbers around until the car drives the way I want it to, and whatever that puts the frequencies at is whatever it puts the frequencies at. The calculated frequency just gives me a nice, easy-to-remember number to quantify how much adjustment I want to make while tuning.


Well, what we don't know is how the ForzaTech engine deals with
- Sprung vs unsprung mass - do tires count?
- Downforce transfer onto springs at different speeds
- weight transfer onto corners while covering, accelerating and braking.
- what are the hidden parameters such as downforce on components that are not unlocked for manual turning.

Given the use of real units and the general fidelity if the rest of the simulation I suspect if we had access to the proper way of dealing with these things our numbers would start to make more sense.

Edited by user Sunday, January 5, 2020 9:20:08 AM(UTC)  | Reason: Not specified

Rank: B-Class Racing License
#39 Posted : Monday, January 6, 2020 3:53:34 AM(UTC)
Originally Posted by: GreenZombie76 Go to Quoted Post
It is heartening to see others interested in the subject of using using using math and science to assist with tuning.

I have some questions as I come from an entirely FH4 background,

I made optional fields in my spreadsheet take the min and max values from the ring rates so it calculates and displays the min and max frequencies available to select in the car you are trying to tune.
I chose cpm rather than Hz as it seems more of a standard in motorsports, and the numbers are more usable (30 and 60 vs .5 and 1 etc).

Display units aside, when I enter the mass and min, max spring rates available to cars like the Mosler in FH4, I get a tiny range of Hz values: 2.5 to 4 - All crazy high.


Almost for that alone, I exclusively use rally suspension. On cars where stiffness isn't as much an issue (like the Mosler) I still use rally, for the extra travel--Maximum Race rear spring rate and ride height on the Mosler or F1GT less effective at keeping off the "bumpstops" than max rate/height with rally.

Also, I did a small study of the default rates in Horizon. You can see it here... https://forums.forzamoto...encies.aspx#post_1074811

Originally Posted by: GreenZombie76 Go to Quoted Post
Well, what we don't know is how the ForzaTech engine deals with
- Sprung vs unsprung mass - do tires count?
- Downforce transfer onto springs at different speeds
- weight transfer onto corners while covering, accelerating and braking.
- what are the hidden parameters such as downforce on components that are not unlocked for manual turning.

Given the use of real units and the general fidelity if the rest of the simulation I suspect if we had access to the proper way of dealing with these things our numbers would start to make more sense.


- Sprung vs unsprung, assuming you mean tires and wheels - I believe the general consensus is no.. personally not sure
- Downforce at different speeds - absolutely yes.. this is standard in most racing games including more arcade-leaning
- Weight transfer - Yes?
- The dev build of FH3 revealed the stock aero values as granting considerably rearward center-of-pressure.

Originally Posted by: Mr Pinstripes Go to Quoted Post
The calculated frequency just gives me a nice, easy-to-remember number to quantify how much adjustment I want to make while tuning.

That's the goal.

Edited by user Monday, January 6, 2020 4:03:48 AM(UTC)  | Reason: Not specified

Rank: S-Class Racing License
#40 Posted : Friday, January 17, 2020 4:00:18 AM(UTC)
I'm unsure as to why you've gone to this much detail when there's a simpler alternative.

You could just find the per-wheel frequency which would give you a ratio between front and rear rebound. Then adjust the bump accordingly as a percentage of the rebound. Do some laps and find out what feels best, job done.

You're also forgetting Forza does have a Fast Bump or Fast Rebound like ACC does. You have to find a middle ground in Forza.
Rank: D-Class Racing License
#41 Posted : Tuesday, January 21, 2020 11:05:28 PM(UTC)
Originally Posted by: EpicEvan777 Go to Quoted Post
I'm unsure as to why you've gone to this much detail when there's a simpler alternative..


erm, because diving into the physics and making spreadsheets IS just as much fun as driving the cars.
Rank: B-Class Racing License
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#42 Posted : Friday, January 24, 2020 9:00:17 PM(UTC)
Originally Posted by: GreenZombie76 Go to Quoted Post
Originally Posted by: EpicEvan777 Go to Quoted Post
I'm unsure as to why you've gone to this much detail when there's a simpler alternative..


erm, because diving into the physics and making spreadsheets IS just as much fun as driving the cars.


Almost. They make each other better.
Rank: S-Class Racing License
#43 Posted : Monday, January 27, 2020 7:51:49 AM(UTC)
Originally Posted by: NumberlessMath Go to Quoted Post
Originally Posted by: GreenZombie76 Go to Quoted Post
Originally Posted by: EpicEvan777 Go to Quoted Post
I'm unsure as to why you've gone to this much detail when there's a simpler alternative..


erm, because diving into the physics and making spreadsheets IS just as much fun as driving the cars.


Almost. They make each other better.

I get that, I like spreadsheets and data too but the data can't be correlated to the game due to a lack of Fast Bunp & Fast Rebound
Rank: C-Class Racing License
#44 Posted : Saturday, March 7, 2020 7:07:52 AM(UTC)
Mr. Math, the Compact V3 tab of the calculator seems to have been switched to read only. The main V3 tab still works. Not sure if something's going on on my end or not, but I thought I should let you know.
Rank: B-Class Racing License
#45 Posted : Wednesday, March 25, 2020 5:59:42 PM(UTC)
Thanks, fixed.
Rank: B-Class Racing License
#46 Posted : Wednesday, January 12, 2022 2:40:54 AM(UTC)
Originally Posted by: Mr Pinstripes Go to Quoted Post
I've run a dozen or so builds/setups through the spreadsheet now, and it does an excellent job of getting a workable setup right out of the box. I do think the frequencies need to be set higher than they would in the real world (probably 2.0 Hz as a dead minimum, and going up from there), as even at 2.2-2.4 the cars I've tested ('65 Shelby Cobra and '73 Porsche Carrera) have barely had enough travel to keep off the bump stops, even with the ride height at or near maximum. That may be an "old car" thing, though.


I found this in a discussion about wheelbase/track width ratio:
"While a suspended vehicle will damp out rough steering inputs to an extent, a kart will expose them in a very upfront way. This in my opinion, is what makes karts such good learning tools."
That's why soft springs are fun: one need not be as precise, or quick to react, to loss of grip. From ~1.5 to ~2.5hz, precision improves at the cost of stability. Somewhere in the upper 2hz range, the tradeoff turns to grip over rough patches vs downforce support/ride height, because at those rates the car is neither relaxed--the springs tend to react faster than the driver and car's yaw are comfortable--so are rarely "behind", nor wanting for precision (unless the damping isn't ideal).

I still have no problem running <2.0hz in Horizon 4, but in 5, it's like you said in FM7, 2.2 to 2.4 is about as soft as is even drivable (on the road). This is curious, as my experience outside Forza has been that softer springs are more relaxed, if not easier to drive outright (when properly damped, not freakishly overdamped like FM4 setups were--that game loved soft springs too). One factor seems to be, the steering is so slow, it often resonates with the roll moment at the rates I'd like to use in A and below: close to and below 2hz...throwing the car into oversteer. And Forza still rejects rather than embracing oversteer, so soft springs can't make a fun, tossable car like they did in FH4.

TL;DR Soft springs give the car a sort of breathing room, averaging the disturbance of driver inputs and bumps, reducing the precision required to work the tires for all they're worth, consistently. It feels like T10 coded the physics to feel that way even on stiff springs...so stiff springs handle oddly but ok, and soft springs are undrivable.

Edit: I have to install FM7 and verify that mildly underdamped setups wasn't the actual reason soft springs gave me trouble. And I know I don't like some aspects of the tires and steering but at least, if I could play it, like FH4 and FH5, pretend nothing about it bothers me and everything is great, wouldn't have to say soft springs are undrivable because of subtly misguided game design goals

Edited by user Wednesday, January 12, 2022 6:35:16 AM(UTC)  | Reason: Not specified

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