Thanks for the equation , I am not that good at maths!
Also It looks like 53% is a good weight balance for no aero.
the way ive been calculating the aero
(rear%) / (front%) * (Chosen Front AERO) i.e. .45/.55*100=81.8
its within 10lbs of your numbers, but it allows me to use a front aero not always tied to 100. my $.02
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With the equation above, you do not need to tie the front aero to 100…it can be anything (within the limits of the Forza dial)!
exactly!!
I meant the equation posted prior to your post…referring to the data…
"This linear equation, based on uber understeer’s aero tests, would be as follows:
RDF = FDF + [258 - 485*(%FW)], OR, FDF = RDF - [258 - 485*(%FW)]
where, RDF = Rear Downforce, FDF = Front Downforce, and, %FW would be the front weight % expressed as a decimal (ex. If 55, it would be 0.55)"
Is the table in the OP recommended for rear wheel drive, FWD, AWD or all?
Eduardo – I’ll let uber confirm if his tests and data included all drive types (or just a specific one). So far, for me, I have done some preliminary tests for both the RWD and AWD and it does provide a close base for then to tweak. I have not checked any FWD’s. Most tricky for me was the mid-engine cars requiring more tweaking.
For me front engine, RWD cars are requiring more tweaking.
My usual start point for grip tunes are 100/180 for front engine, RWD cars. I then tweak from there using both suspension and aero to get turning I want at all speeds. Most of the tunes I finish with have at least 180 on rear (assuming production car with standard Forza wings). Cutting that in half on the rear means big changes elsewhere to ensure I do not suffer oversteer.
If tuning for the Alps I have used less rear df but maybe around 160.
Speed tracks have had less aero on both front and rear but similar balance to my 100/180.
Have I been doing it wrong? No doubt but I have not seen many open source tunes running aero ratios like this so it is all quite surprising.
I am not trying to criticise it. It obviously gains a few mph and allows better turning at speed but I have so far not been able to balance that out. I can only assume I am being stubborn trying to change things like ARB or damping to re stabilise the car. I am changing them but getting reluctant to change them more but am oversteering as a result. Maybe I need to further adjust my driving. Or just conclude low rear aero is not for me.
EDIT: the figures in the OP I already use on FWD and am close on AWD, just not on grip based RWD cars.
1st equation: Rear Down Force=Front Down Force (you wanna use) + ( 258 - ( 485 * Car_WeightDistribution_Front ) )
2nd equation: Rear Down Force=( Car_WeightDistribution_Rear / Car_WeightDistribution_Front ) * Front Down Force(you want to use)
The 2nd Equation will give you the most neutral base setup. The easiest way to test this is with a %50 FW car. The first equation you will get 75LBS Front DF and 90.5Lbs Rear DF. With the 2nd equation you get 75 LBS Front DF and 75LBS Rear DF. Knowing that the car is already balanced (%50 FW) You can conclude that the last equation gives the most Neutral Aero set-up with 75 Lbs front and back to maintain that %50 balance.(the center of gravity of the car will be dead center) by manipulating the Front and Rear Aero you can move the center of gravity around(Center, Front, Back)and creating a Neutral, under-steering or over-steering Aero setup Just like in real life.
. It’s car and track specific. Just like pretty much all other tun-able parts the stock Aero set-up( 75 front and 137back) that Forza gives you is not the best one as far as balance goes. It’s all over the place sometimes it’s OK other times it’s plain WRONG. It’s that way to make it easier to drive. Sometimes Stock tune is fine sometimes it needs tweaking. Every situation is unique. and every driver like the car balanced a certain way. Some of us like some under-steer. some can’t get enough over-steer this Set-up is Neutral. The car wil go faster have better weight distribution and turn better. Just my opinion. And you have to test every time and see what suits you, the car and the track best…Again I’m only basing this on my personal experience.
Psycho…in your opinion (for most of the time/cars), you believe the car will go faster with the “neutral (including aero)” distribution, i.e. equation #2? Just wanted to make sure I got that correct! Thanks!
The math shows that the 2nd equation is more NEUTRAL.Im not saying better or worst.( i’ve been testing the first equation only the past couple of days) I like the feel of Uber’s equation better just because it has a slight under-steer in it. But both r very good in my opinion. I have been using the neutral one as a starting point to all my builds. But you will encounter some weird situation like the example of the Lexus LFA where Front aero max is 54 lbs with a %49 FW. Try it you’ll see what I mean. But both equations will give a far more stable Aero setup than the stock one and Faster. Again this only MY OPINION…Another thing to keep in mind your suspensions settings have to also match your aero setup or it won’t work!
I agree, both of these equations will provide you with a more stable aero configuration versus the default Forza setup. I have been doing a little bit of testing and do prefer the 1st equation derived from uber’s test data. I prefer it since it keeps the rear a little bit more stable, though, as you say it provides some understeer. I’ll try the LFA…
On the aero and suspension match…I start with the springs total (as an x% of total weight) and apply the distribution (though sometimes they need to be reversed for mid-engine and/or awd). From there, I adjust the springs for more/less turn-in and/or over/understeer. Then I adjust the aero as required. Do you go back and redistribute your springs to match required aero? Or the other way around (aero to match springs dist)? Or, keep the springs as-is?
Its done on balance not speed, not drag , not downforce, not lap time just purely balance, (no change in balance from slow speed to high speed).
I used what ever car I had and noted its weight %. I used AWD for the 60% and high front ones and RWD for the rest. I also DON’T use TC so my springs might be more understeery resulting in a more oversteery aero (from lack of grip/ traction from slow speed corners).
Thanks for clarifying this Uber.
I’m using 85 lb Front Aero Downforce.
Car_WeightDistribution_Front = 55%
Car_WeightDistribution_Rear = 45%
With uber understeer’s lookup I get the following results:
· Front Aero Downforce: 85
· Rear Aero Downforce: 76
With PRKid’s formula I get the following results:
85 + ( 258 - ( 485 * Car_WeightDistribution_Front ) )
· Front Aero Downforce: 85
· Rear Aero Downforce: 76
With grgus’ formula I get the following results:
( Car_WeightDistribution_Rear / Car_WeightDistribution_Front ) * 85
· Front Aero Downforce: 85
· Rear Aero Downforce: 70
Is 75/75 really neutral? Front range is usually 50-100, Rear range is usually 75-200.
So you are placing the front in the middle but the Rear at the lowest setting.
Plus we really don’t know what the LB of the aero means. I am using Bernoulli’s equation against the aero downforce as part of my spring adjustments; but I have no way of knowing what the width is to get a proper lbf/in.
So anyways, 75/137 is actually the “neutral” if you go by the min/max of the front and back aero adjustments.
Yes in the example I gave 75/75 is Neutral. And Lb = Pound If you switch the unit to metric(I’m used to metric so that what I use. I’m French:) ) it will change to kg=Kilogram
Example a car that weighs 2000 LBS and has 50% Front weight means the front weight is 1000lbs and the back also= 1000lb with 75lbs front and 75lbs back you keep that balance. otherwise you are shifting the weight to front or to the back. So yes it’s Neutral. And neutral does NOT mean best it’s just Neutral Aero weight distribution…
In my opinion most cars I have tested the stock Tune is always off. Sometimes by a little other times by a lot. I mean when you put a race Diff on a car the stock tune is 75/75 acceleration and deceleration is that correct? I don’t think so! I can go on and on about the stock tune numbers.The closest thing to perfection I came across in terms of stock tune numbers is the Ferrari 312 T2.
PS: I have seen this on the French Forums long time ago 
Does placing the value of the front aero to 75 lb, really mean you are adding 75 lbs to the weight of the front of the car?
Can such a small amount of weight (50-100) really cause so much under/oversteer?
I don’t think we really know what that LB means.
Usually aero is not a static weight, but is based on car speed and air flow.
Just my thinking. It doesn’t matter really, but you drive the dang thing for days over and over until everything is just right, so the meaning of the number itself doesn’t matter.
You just have to understand all the interlocking values when you tweak just one value like front aero.
It is a major pain, Why can’t Forza tune their cars?
They can run all the maths and drive simulations and give us something closer to drivable, instead of the pieces of kitty litter they give us.
Yes, they can do it for every single possible build combination. It isn’t hard, the knowledge is out there, the tech is out there.
Yes in the example I gave 75/75 is Neutral. And Lb = Pound If you switch the unit to metric(I’m used to metric so that what I use. I’m French:) ) it will change to kg=Kilogram
Example a car that weighs 2000 LBS and has 50% Front weight means the front weight is 1000lbs and the back also= 1000lb with 75lbs front and 75lbs back you keep that balance. otherwise you are shifting the weight to front or to the back. So yes it’s Neutral. And neutral does NOT mean best it’s just Neutral Aero weight distribution…
In my opinion most cars I have tested the stock Tune is always off. Sometimes by a little other times by a lot. I mean when you put a race Diff on a car the stock tune is 75/75 acceleration and deceleration is that correct? I don’t think so! I can go on and on about the stock tune numbers.The closest thing to perfection I came across in terms of stock tune numbers is the Ferrari 312 T2.
PS: I have seen this on the French Forums long time ago (Same GT)
I agree with your logic. I’m not arguing with it.
I’m just wondering if that aero value is really a static weight on the car. Forza doesn’t give us enough info. If it is a static weight value, then why is it in aero? Why not just call it lead weight?
No argument from me Psycho. you are correct about Neutral.