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#1 Posted : Wednesday, October 7, 2015 12:26:20 AM(UTC)
Warning you need to be good at maths.


Ok guys and girls. Here's the formula to work out your spring rates for the car.
F= chosen frequency
MS= sprung mass (kgs)
MR= Suspension travel rate
K= Spring rate

K=4 x pi squared x F x square root MS x MR squared

Frequency = 2-6
Low downforce (superminis, city cars, hatchbacks, saloons, estates, trucks, vans,) = 2-3.5
Med downforce (Sports and super cars Ferrari, Lamborghini, lotus etc) = 3-4.5
High downforce (FIA/MSA race/touring cars/single seaters) = 4.5-6

Suspension travel rate
1.25, 1.35, 1.45 choose which rate fits the your style. The higher the rate the stiffer your springs.

Sprung mass
2506/4=626.5 (284kg)
(Total weight / 4 wheels= Sprung mass).

Chosen travel rate
1.45

Chosen frequency
2.5

Put it together

4 x PI squared x 2.5 x square root (284)x 1.45 squared =3496.99

Spring rate =349.69nm (after dividing 3496.99 by 10)
Add or subtract the difference in weight distribution

So for 43/57 it should look like this.
Front
349.69 - 7%=

Rear
349.96 +7%=

The result should be the perfect Spring rate for that car to deliver optimum weight transfer while minimising dive, maximising grip.

Example set ups
Soft set up (Ferrari 250 Berlinetta Lusso)
ARBs
12.16
9.41
Springs and ride height
249.6
239.5
8.1
7.9
Damping
6.5
6.8
6.8
6.3

Hard set up (Toyota Supra)
ARBs
26.52
18.16
Spring and ride height
572.9
713.4
6.0
5.8
Damping
8.3
7.9
5.6
4.9

See how with the softer set up I set the ARBs softer to allow the body to roll loading the tyres?? I've also got a higher bump stiffness to control the pitch and drive, allowing me to set the rebound lower to smooth the ride. So the damping is controlling the ride over all stability, ARBs are controlling tyre loading and springs are allowing more movement to give more grip using all 3 springs efficiently. You'll need to run more camber at the front with a lower caster to rule out excessive camber while turning.

The hard Set up we see the opposite effect. I've got a much bigger ratio between bump and rebound. If you boost the rebound on stiff springs you'll be skating over the track instead of griping to it, so we reduce the bump, increase the rebound to give a more complaint set up. What we also do it because we with this set up don't want as much roll, we boost the ARBs considerably to provide a "flat ride" this will let you run with less camber putting more of the tyre on the track at any time generating extra grip. To compensate for the reduced camber however we need to boost the caster angle to aid turn in and exit grip.

The stiffer set up creates a less compliant car that is also much less predictable. Just as fast in the right hands but much harder to score consistently quick laps with.

Fixed.

Edited by user Tuesday, October 27, 2015 12:53:57 PM(UTC)  | Reason: Fixed the formula works any combination now.

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#2 Posted : Wednesday, October 7, 2015 1:30:05 AM(UTC)
Originally Posted by: About500Rabbits Go to Quoted Post
Warning you need to be good at maths.


Ok guys and girls. Here's the formula to work out your spring rates for the car.
F= chosen frequency
MS= sprung mass
W= weight per corner
MR= Suspension travel
K= Spring rate

K=4 x pi squared x F squared / MS x W x MR squared

Frequency = 0.5-5+
Low downforce saloon = 0.5-1.5
Med downforce sports car = 1.5-3
High downforce racer = 3-5+

Pt1.
Weight per corner 2506/4=626.5
(Total weight / 4 wheels= weight per corner)

Pt2.
Sprung mass 626.5-10% (we don't know what the actual figures are for the wheels etc so we're deducting a round about number)

626.5-10%=563.85

Pt3.
Suspension travel you looking fully for fully compressed (bottomed out) usually between 1.25-1.45 excluding trucks.

Put it together

4 x PI squared x 2.5 squared / 563.85 x 626.5 x 1.45 squared =576.4

Spring rate =576.4
Add or subtract the difference in weight distribution

So for 43/57 it should look like this.
Front
576.4-7%=

Rear
576.4+7%=

The result should be the perfect Spring rate for that car to deliver optimum weight transfer while minimising dive, maximising grip.

Damping to follow.




I usually just round about guess.... but i keep picking up bits, thanks for this, i usually just adjust the suspension till it feels right but this looks like a decent formula :)
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#3 Posted : Wednesday, October 7, 2015 1:33:03 AM(UTC)
Excellent post. Could the sprung mass of the car not be deduced based on the size of the wheels and a reasonable estimate of the wheel density? Or is that sort of what you did here?
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#4 Posted : Wednesday, October 7, 2015 1:47:53 AM(UTC)
You do realise that this is much like the tuning calcs and only good for a round about average tune???

To get to the top of the heap you need to forget reality.

Real world expectations do not equal in game performance.
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#5 Posted : Wednesday, October 7, 2015 1:52:52 AM(UTC)
Originally Posted by: Will Driver C Go to Quoted Post
Excellent post. Could the sprung mass of the car not be deduced based on the size of the wheels and a reasonable estimate of the wheel density? Or is that sort of what you did here?


That's pretty much what I've done. I presume the difference of 10% is about right as the unsprung weight is dynamic based on wheels, brakes, and a few unknowns. You may get away with 15% if you're really pushing but an estimate of 10% I think Would be about right.

It's what it worked out as on a motorbike with forged mag wheels and carbon rotors. So assuming that the theory behind it is the same the ratio should be the same.
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#6 Posted : Wednesday, October 7, 2015 4:12:35 AM(UTC)
The suspension model used in this game bears little evident relation to the real world. You're better off studying the math buried within the game itself.
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#7 Posted : Wednesday, October 7, 2015 4:30:46 AM(UTC)
About500rabbit. Good maths, I may try it once, but like the others have said thats really only good for a base. Plus you keep mentioning sprung/unsprung weight. I am 90% sure that forza does not differentiate between sprung and unsprung weight. To forza it is just total weight otherwise rim upgrades would be much more beneficial than they are.

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#8 Posted : Wednesday, October 7, 2015 5:33:27 AM(UTC)
I know the game doesn't differentiate between sprung and unsprung weight but it's needed for the calculation. Have a formula set up F40 which is currently lapping 3 seconds faster than it was before tuning and only suffers from 1 wheel breaking traction in the turns so on a grip basis it does work positively. So it's not a case of being just a base tune. setting the springs up to deal with the weight and distribution on the car is vital to creating a balance. To generate the optimum you need to have the the suspension, ARBs and damping working in harmony even in this game.

I'm not saying it's fool proof or that it should replace tuning by feel, but it's there to balance the chassis. What you do is Upton you. Try it, if it doesn't work for you that's fine, if it does that's fine also.

Will upload the F40 with formula based suspension and ARBs when I'm finished at work. Will a version of the car without adjustable aero and you can try it and feed back.
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#9 Posted : Wednesday, October 7, 2015 8:36:26 AM(UTC)
Tuning to me is like cooking, you can follow a recipe book with pictures and all but its always going to need something else for your taste, formulas are created for a "BASE" but understanding what you're trying to create is the key....alittle bit of this, a little less of that and BINGO, the perfect dish....lol...

Edited by user Wednesday, October 7, 2015 8:37:53 AM(UTC)  | Reason: Not specified

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#10 Posted : Wednesday, October 7, 2015 8:46:01 AM(UTC)
Originally Posted by: About500Rabbits Go to Quoted Post
Warning you need to be good at maths.


Ok guys and girls. Here's the formula to work out your spring rates for the car.
F= chosen frequency
MS= sprung mass
W= weight per corner
MR= Suspension travel
K= Spring rate

K=4 x pi squared x F squared / MS x W x MR squared

Frequency = 0.5-5+
Low downforce saloon = 0.5-1.5
Med downforce sports car = 1.5-3
High downforce racer = 3-5+

Pt1.
Weight per corner 2506/4=626.5
(Total weight / 4 wheels= weight per corner)

Pt2.
Sprung mass 626.5-10% (we don't know what the actual figures are for the wheels etc so we're deducting a round about number)

626.5-10%=563.85

Pt3.
Suspension travel you looking fully for fully compressed (bottomed out) usually between 1.25-1.45 excluding trucks.

Put it together

4 x PI squared x 2.5 squared / 563.85 x 626.5 x 1.45 squared =576.4

Spring rate =576.4
Add or subtract the difference in weight distribution

So for 43/57 it should look like this.
Front
576.4-7%=

Rear
576.4+7%=

The result should be the perfect Spring rate for that car to deliver optimum weight transfer while minimising dive, maximising grip.

Damping to follow.



This formula could not possibly work in this format. Leaving all other numbers the same, replace 563.85 with 90 and 626.5 with 100 and you get the same end result. Basically as long as this 2 numbers are 10% different it yields the same supposed spring rates. It doesn't take weight into account at all.

Unless I missed something.
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#11 Posted : Wednesday, October 7, 2015 8:55:47 AM(UTC)
Originally Posted by: DoubleDown Doug Go to Quoted Post
Originally Posted by: About500Rabbits Go to Quoted Post
Warning you need to be good at maths.


Ok guys and girls. Here's the formula to work out your spring rates for the car.
F= chosen frequency
MS= sprung mass
W= weight per corner
MR= Suspension travel
K= Spring rate

K=4 x pi squared x F squared / MS x W x MR squared

Frequency = 0.5-5+
Low downforce saloon = 0.5-1.5
Med downforce sports car = 1.5-3
High downforce racer = 3-5+

Pt1.
Weight per corner 2506/4=626.5
(Total weight / 4 wheels= weight per corner)

Pt2.
Sprung mass 626.5-10% (we don't know what the actual figures are for the wheels etc so we're deducting a round about number)

626.5-10%=563.85

Pt3.
Suspension travel you looking fully for fully compressed (bottomed out) usually between 1.25-1.45 excluding trucks.

Put it together

4 x PI squared x 2.5 squared / 563.85 x 626.5 x 1.45 squared =576.4

Spring rate =576.4
Add or subtract the difference in weight distribution

So for 43/57 it should look like this.
Front
576.4-7%=

Rear
576.4+7%=

The result should be the perfect Spring rate for that car to deliver optimum weight transfer while minimising dive, maximising grip.

Damping to follow.



This formula could not possibly work in this format. Leaving all other numbers the same, replace 563.85 with 90 and 626.5 with 100 and you get the same end result. Basically as long as this 2 numbers are 10% different it yields the same supposed spring rates. It doesn't take weight into account at all.

Unless I missed something.



....... :face palm: back to the drawing board.. What did I miss..

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#12 Posted : Wednesday, October 7, 2015 9:03:38 AM(UTC)
Originally Posted by: About500Rabbits Go to Quoted Post
Originally Posted by: DoubleDown Doug Go to Quoted Post
Originally Posted by: About500Rabbits Go to Quoted Post
Warning you need to be good at maths.


Ok guys and girls. Here's the formula to work out your spring rates for the car.
F= chosen frequency
MS= sprung mass
W= weight per corner
MR= Suspension travel
K= Spring rate

K=4 x pi squared x F squared / MS x W x MR squared

Frequency = 0.5-5+
Low downforce saloon = 0.5-1.5
Med downforce sports car = 1.5-3
High downforce racer = 3-5+

Pt1.
Weight per corner 2506/4=626.5
(Total weight / 4 wheels= weight per corner)

Pt2.
Sprung mass 626.5-10% (we don't know what the actual figures are for the wheels etc so we're deducting a round about number)

626.5-10%=563.85

Pt3.
Suspension travel you looking fully for fully compressed (bottomed out) usually between 1.25-1.45 excluding trucks.

Put it together

4 x PI squared x 2.5 squared / 563.85 x 626.5 x 1.45 squared =576.4

Spring rate =576.4
Add or subtract the difference in weight distribution

So for 43/57 it should look like this.
Front
576.4-7%=

Rear
576.4+7%=

The result should be the perfect Spring rate for that car to deliver optimum weight transfer while minimising dive, maximising grip.

Damping to follow.



This formula could not possibly work in this format. Leaving all other numbers the same, replace 563.85 with 90 and 626.5 with 100 and you get the same end result. Basically as long as this 2 numbers are 10% different it yields the same supposed spring rates. It doesn't take weight into account at all.

Unless I missed something.



....... :face palm: back to the drawing board.. What did I miss..



I know where I went wrong I'll correct it later.

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#13 Posted : Wednesday, October 7, 2015 9:52:38 AM(UTC)
Originally Posted by: DUST2DEATH Go to Quoted Post
You do realise that this is much like the tuning calcs and only good for a round about average tune???

To get to the top of the heap you need to forget reality.

Real world expectations do not equal in game performance.


every time I try to adjust realistically, usually feels weird. In game the tunes get funky
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#14 Posted : Wednesday, October 7, 2015 4:12:53 PM(UTC)
Fixed the formula.... I misunderstood the theory so added irrelevant figures. Errors have been corrected now and the formula amended to work with Forzas laws of physics. Please try it and give me some feedback please, am working on ARBs and damping... Just need to figure out how to get the relevant data from the telemetry.
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#15 Posted : Thursday, October 8, 2015 3:55:43 AM(UTC)
This is all very interesting, but I'm no mathematician. Isn't the "square root of PI squared" just PI?
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#16 Posted : Thursday, October 8, 2015 4:50:17 AM(UTC)
Just by means of logic and not math i would say yes.

Square root is the number in which ( YxY=y^2) Transversly sq rt y^2 = y
Y=PI

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#17 Posted : Thursday, October 8, 2015 5:03:06 AM(UTC)
Originally Posted by: gtFOOTw Go to Quoted Post
This is all very interesting, but I'm no mathematician. Isn't the "square root of PI squared" just PI?


Yes. The square root of any number squared is just that number.

Speaking of suspension formulas to use a base before fine tuning, what's wrong with:

(total Weight / 2) * front weight % = front spring
(total weight / 2) * rear weight % = rear spring

I mean, it's not the end result it's only a base and it is far less complicated....

Edited by user Thursday, October 8, 2015 5:04:18 AM(UTC)  | Reason: Not specified

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#18 Posted : Thursday, October 8, 2015 5:05:51 AM(UTC)
Originally Posted by: PPiDrive Go to Quoted Post
Originally Posted by: gtFOOTw Go to Quoted Post
This is all very interesting, but I'm no mathematician. Isn't the "square root of PI squared" just PI?


Yes. The square root of any number squared is just that number.

Speaking of suspension formulas to use a base before fine tuning, what's wrong with:

(total Weight / 2) * front weight % = front spring
(total weight / 2) * rear weight % = rear spring

I mean, it's not the end result it's only a base and it is far less complicated....


And it doesnt bring in factors which arent relevent to forza.

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#19 Posted : Thursday, October 8, 2015 5:49:26 AM(UTC)
Originally Posted by: PTG Baby Cow Go to Quoted Post
Originally Posted by: PPiDrive Go to Quoted Post
Originally Posted by: gtFOOTw Go to Quoted Post
This is all very interesting, but I'm no mathematician. Isn't the "square root of PI squared" just PI?


Yes. The square root of any number squared is just that number.

Speaking of suspension formulas to use a base before fine tuning, what's wrong with:

(total Weight / 2) * front weight % = front spring
(total weight / 2) * rear weight % = rear spring

I mean, it's not the end result it's only a base and it is far less complicated....


And it doesnt bring in factors which arent relevent to forza.


so suspension travel you say is not relevant?? Neither is downforce or oscilation frequency??? Ok then prove it. Go buy any car you want, set your springs as soft as you can along with damping and rollbars then post the video of the hot lap. Then go do the opposite set them as hard as you can and do a hot lap and post the video for us to see. It'll be very entertaining for everyone as a lesson goes.

It is far less complicated but there's also a difference of 400 in the numbers generated. Call me picky but the system of just relying on the cars weight assumes your vehicle is in a constant state and doesn't take into account the vehicle dynamics.

Ok best way I can explain it is going to the extreme. Your calculations results in a spring stiffness of 1732.9 on a ford raptor, my calculations brings it in at 1384.2. The weight is the same for both calculations as is the distribution..

My calculation
4 x pi squared x frequency (oscillations) x square root of mass X suspension travel =

Before people try and slate and say that I'm considering invalid data in the calculation maybe drive the shared F40. If you still feel that way fine. At least you're not writing it off right off the bat.

Edited by user Thursday, October 8, 2015 5:50:12 AM(UTC)  | Reason: Not specified

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#20 Posted : Thursday, October 8, 2015 7:00:23 AM(UTC)
You cant access the data for suspension travel with proper numerical values. All you know is the ride height. Sure you can punch a number in there based on if you would like a stiffer car with little to no suspension travel or a very soft floaty vehicle with lots of suspension travel, but none the less it is still guess work.

I am not sure how making a car as soft as possible or as stiff as possible has anything to do with the relevancy of suspension travel or aerodynamic downforce in this scenario. I would never put on the softest springs or the stiffest spring and the softest dampening.

Edited by user Thursday, October 8, 2015 7:03:31 AM(UTC)  | Reason: Not specified


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#21 Posted : Thursday, October 8, 2015 7:42:31 AM(UTC)
Originally Posted by: PTG Baby Cow Go to Quoted Post
You cant access the data for suspension travel with proper numerical values. All you know is the ride height. Sure you can punch a number in there based on if you would like a stiffer car with little to no suspension travel or a very soft floaty vehicle with lots of suspension travel, but none the less it is still guess work.

I am not sure how making a car as soft as possible or as stiff as possible has anything to do with the relevancy of suspension travel or aerodynamic downforce in this scenario. I would never put on the softest springs or the stiffest spring and the softest dampening.


Do you actually look at the telemetry at all and use the information it's giving you??? Obviously not.
If you did you'd know that you can get the info for the suspension travel from the telemetry no guesswork involved there.

Maybe you should try a car with the softest and then the stiffest settings with 0 downforce and maximum downforce.. You'll answer your own question.

Meanwhile here's a basic description on how suspension works.
http://auto.howstuffworks.com/car-suspension.htm

Downforce pushes down on the car using its suspension travel so you need to stiffen the springs to prevent the car bottoming out. It's related to suspension travel and not ride height as demonstrated in F1.

Running any downforce requires you to stiffen the springs to limit Spring compression and with that suspension travel to prevent you from bottoming out.

Setting a car up for 2000lbs with no added downforce then adding 400lbs of downforce give the car a total mass of 2400 as far as suspension settings are concerned, not 2000. That's 400lbs extra that you're not accounting for in the set up which will affect handling and stability as well as braking and acceleration.

Edited by user Thursday, October 8, 2015 8:00:24 AM(UTC)  | Reason: Not specified

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#22 Posted : Thursday, October 8, 2015 8:46:10 AM(UTC)
Yes i understand how a suspension works. However aero is a variable number. Just because you set it for 400lbs does not mean it is always 400 lbs. It is not adding static weight to a vehicle. Also, nowhere does it demonstrate suspension travel in a non relative to the vehicle number. suspension travel is not something like 8" on the vehicle. If it is provided in a number (i dont believe it is) it is a number that changes based on the vehicle. It is not a constant number as in if you make it 4" on vehicle a 4" on vehicle b they are now the same. They are a value based on each individual vehicle, which has a set of minimum and max values preinput by the developers, no matter how much tweaking you do to your settings you are unable to change this unknown value.

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#23 Posted : Thursday, October 8, 2015 9:16:49 AM(UTC)
Originally Posted by: PTG Baby Cow Go to Quoted Post
Yes i understand how a suspension works. However aero is a variable number. Just because you set it for 400lbs does not mean it is always 400 lbs. It is not adding static weight to a vehicle. Also, nowhere does it demonstrate suspension travel in a non relative to the vehicle number. suspension travel is not something like 8" on the vehicle. If it is provided in a number (i dont believe it is) it is a number that changes based on the vehicle. It is not a constant number as in if you make it 4" on vehicle a 4" on vehicle b they are now the same. They are a value based on each individual vehicle, which has a set of minimum and max values preinput by the developers, no matter how much tweaking you do to your settings you are unable to change this unknown value.


No but you can take the figure of fully compressed and fully extended. The difference is your travel it's really not rocket science that.

No where did I say the downforce is a constant either but you still need to account for that extra mass when setting the springs up! This really isn't rocket science buddy.

You don't set suspension up around at 2000lb car knowing you've got potentially 400lbs of extra mass from the downforce you're generating. You set it up to deal with the potential total of 2400 not 2000.

As for you're "I don't believe the numbers are given" look at your compression graph unless I'm hallucinating the numbers are given quite clearly.

Edited by user Thursday, October 8, 2015 9:21:49 AM(UTC)  | Reason: Not specified

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#24 Posted : Thursday, October 8, 2015 10:09:42 AM(UTC)
I dunno man. I'm pretty sure most of us just want to drive video game cars fast without having to enroll in a physics class. I do respect your work however, you either had to have spent alot of time thinking about all this or you plagerized the hell out of someone who did. Eh, either way...nice job
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#25 Posted : Thursday, October 8, 2015 10:09:57 AM(UTC)
You all understand nothing and LOL to the guy using math that said he tuned cars as well as I did.

Downforce is also a constant in Forza, it doesn't increase or decrease depending on your speed. It's always 400lbs or driving vehicles on the limit would get you more grip, not less much like an F1 driver getting more out of the same car than someone who couldn't keep the tires warm.

Also this game doesn't factor in suspension travel based upon the car. When you upgrade a suspension on a stock vehicle that vehicle has the same generic suspension underneath it as every other car that has been upgraded. The Honda and the Nissan and the Ford all turn into a Forza. It's why the same settings (or area on the slider) work on nearly every single car.

Edited by user Thursday, October 8, 2015 10:13:02 AM(UTC)  | Reason: Not specified

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