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The formula is an average which works on most tracks. The high rebounds come from personal experience (which cannot be formulated) on certain tracks when in Leaderboards.
RR

I too seem to be getting some very low numbers for the damping, specifically under 3 rebound and 1.2 bump for my m3 i built today. This seemed to work really well or the DBR9 that I tried it with, but the M3 seems to bottom out constantly.
This is a fantastic system, and I now use it any time I tune a car (to the extent that I have a spreadsheet on my google drive to allow me to do all of it in one go).
But the really low numbers may be a slight issue...

I'm curious as to how you derived your formula?

The units for your final damping answers aren't accurate. The units for damping are generally Ns/mm and i believe this is what they use in forza.

Converting your formula to only take into account the units we get:

(kg * m/s^2)/(N/m * m^2)

The weight distribution is a percentage and therefore has no units. I'm guessing that the 9.8 constant you included refers to "g", the acceleration due to gravity on earth which has the units m/s^2. Lbs has been converted to kg. If you want to use Lbs, you should use a value of 4.45 instead of 9.8.

Looking at just the top half of your formula we have:

kg * m/s^2 aka Newtons second law of motion Force=mass*acceleration so this gives us a final unit of N for the top half.

Looking at the bottom half:

N/m * m^2 = Nm

So now the total formula has been simplified to:

N / Nm

Which gives us the final unit of 1/m which can be converted to 1/mm by dividing the value for 1/m by 1000. So its close to the correct units for damping but not quite there.

I'm currently studying motorsport engineering at university. The way we go about damper tuning is shown in this presentation http://kaztechnologies.c..._Calculation_Seminar.pdf

It's pretty long but super detailed and tells you pretty much everything you could ever want to know about damping.

I know the formula isn't exactly accurate as it's just a general formula.
The formula is one which I created in FM3 when I was thirteen, so obviously it's not going to be 'university' accurate.
I'll take a look at that presentation though, and thanks for posting it!
RR

I have done the same in the past, tried to apply my real world knowledge to the game, problem is that some really unbelievable and funny settings work in this game which just can't in real life, like back in FM2 where everyone used to set up cars super soft yet with max downforce, that just can't work in real life, so it wouldn't be beyond my expectations that they still haven't got it right now.

I'm currently doing Mechanical Engineering by the way, I learn all the automotive stuff in my spare time, though most/all can be derived from what I get taught anyway.

I think RRs tunes are top notch. I have tried several and am always impressed with how creative and effective they are. Truly a fan of his tuning.

But the answer is simply that the formula is just plain fudged. RR knows and most tuners know what range of numbers work for settings.
Steps to create new formula...
1. Learn which settings are effective
2. Factor for weight distribution
3. Include real word constants for some pizzazz
4. Fudge numbers til you get desired results *most* of the time

Now thats not good or bad though!

I used the formulas for a little while and found myself plugging in numbers and then building everything else around those calculated figures to make them work. This did not work best for me at all. And nobody, including RR ever claimed these figures to be perfect. But as a GREAT open source tuner, and also as a person willing to share what he uses for baseline tunes, and where to begin, I think he has done a great job overall.

I think the issue is dividing by the ride height squared. This provides some good numbers when the ride height is around the mid 3" range (ie 3.5 or so) but starts to divide by a really big number, making the damping settings small, when the ride heights get larger. Espically around 7" or more.

The bump settings are low because the equation divides by max spring setting. So no matter the ride height, the bottom of the equation that you are dividing by is always going to be large compared to the top part of the equation.

My guess is that the 9.8 constant could be changed to a variable based on ride height and would produce more realistic numbers. But it would take some research and would be much more complicated.

Hey i'm doing this with an NSX GTR on Forza 4
Weight = 2247
Front Weight = 0.44
Low spring rate = 116.4
Upper spring rate = 872.9
Front Ride height = 5.8
Rear Ride height = 5.1

For front bump
(2247 * 0.44 * 9.8) / (872.9 * 5.8^2) + 1 = 1.329
Is this right?

Hey roadrunner hows it going dude!? Found this and was intrigued to use it but the formula doesn't seem to work. By which I mean there is no result... I may be doing somthing wrong Idk.
* = multiply correct?
I did a copy paste of your example
((46% (1422) * 9.8) / (73.7 * 3.5^2)) + 1 = 8.1
Then replaced figures with my own and not getting anything lol.
((54%(2,933)*9.8)/(152.0*4.2^2))+1=????
If you get this please reply directly I will likely recieve it quicker.
Thanks 😉👍

Edited by user Saturday, February 11, 2017 9:55:57 AM(UTC)  | Reason: Not specified

Hey xCeasars

Yes * does mean multiply. Using your fomula in Excel as you have wrote gives an error
((54%(2,933)*9.8)/(152.0*4.2^2))+1=????

if you add "*" after the 54% and removed the "," in 2933 as below this will give you 6.8 to the nearest decimal point
((54% * (2933)*9.8)/(152.0*4.2^2))+1

Edited by user Saturday, February 11, 2017 11:56:21 AM(UTC)  | Reason: Not specified

Hey Hanson how are you man, that makes alot more sence now lol thanks for that. Somthing interesting this never seen this method before, thought I'd give it a go to see how it fairs 😊👍

Hey xCaesars, I'm still around been play FH3 using strange PI numbers (not maxing out the class) as I'm not a big fan of AWD and max HP.
I remember looking at the formula and had similar issues to some people who have posted in the thread that a lot of my rebound figures sat between 5 and 7 which is a bit soft for me (I prefer 8 to 9).
I'm not sure if it is this thread or another, but I remember reading that someone mentioned that the bump should be the square root of the rebound. In your example above, this would be 2.6.

My guide is a rough setup for bumps and rebound but yea I usually settle between 7 and 10 rebound depending on cars wieght. The bump is said to be set between 50% and 75% of rebound, a setting 66% to work out bumps is a happy medium.
I've never her heard of that square root version before but I have had tunes from others with similar low values and have work relatively well.

Edited by user Saturday, February 11, 2017 2:08:03 PM(UTC)  | Reason: Not specified

Haha exactly. You still remember school. Is a distant memory for me hahah