This is my tune for the C9 in the Group 3 event. The Car handle well but I end up dusted in acceleration when exiting a corner. I add some screenshot of my setup. Any advice is more than welcome.
try lowering the springs a lot and increase the dampers to around 5.0 bump and around 10.0 to 11.0 rebound. Put the tire pressure to 2.0 - 2.1 and try to lower the rear aero as much as possible, you shouldn’t need more than 300. And reduce camber, you should have more camber in the rear cause forza is a bit weird in that regard.
I have different approach to tunning than meta tuners, (but my cars are fast) and I also use stiff springs, but your rebound is defo too high
High rebound = high speed understeer
Low rebound = high speed oversteer
High bump = low speed understeer
Low bump = low speed oversteer
And I usually just use 100/0 diff in all cars just for better rotation when accelerating, and so that all power goes where it need while accelerating.
Also gearing… ultra weird, lol usually u setup gears in a way so that in lower speeds u don’t have to shift so often, while in higher speeds u need closer gearing to use most of peak power.
Alignment seems fine, whatever, tyre pressure seems bit too low (just look at telemetry and how tyres heat up in corner)
Btw u can use this much rear downforce but then your rebound needs to be ~ 4.0 or something like that to counter this much understeer from downforce.
They are referring to the Merc Sauber C9, for the spec build event this week.
Looking at the Lat G numbers, most of the shared tunes by people I recognise seem to be running Lat G numbers consistent with having very low rear downforce. Without doing any testing, I suspect that’s the main difference.
Maybe it’s too obvious to point out, but are you using TCS at all? That could severely ruin your acceleration.
Nope, I use TCS just for X car
I drove that merc c9 today and it feels pretty quick but the grip is just not quite there. Is this why you went almost full aero on it? So instead of actually fixing the grip problem you made it slower.
If it was any other /lower class car you could probably add more Hp on it and then go full aero so even if it hurts the top speed it would’t matter that much. But P class … racing on those full circuits, you need all the speed you can get.
Even if your downforce is low or lowish, it doesn’t mean the car shoudn’t feel as grippy. I think what we have access to in terms of tuning is like a second-layer type deal. Like we’re overwriting it on top of the tunning that’s already been done to the car behind the scenes. Theres definitely things that we simply can not see in the current simplyfied version that’s been given to us.
Which leads me to think that if you’re looking for more grip, you should look for it elsewhere, not specifically in the aero section of the tuning. Especially on these higher PI class cars. And in your specific case, with your own tuning done to the car i think you can look for it in the springs, tire pressure, differential, rebound stiffness…
If i get a chance to race with the car again id try and see if i can find a way to get that extra grip. But sadly the event will be gone pretty soon, so maybe i wont be able to.
I was racing under the rain and yes: I feel the C9 got less grip compared to the Nissan or the 787B Mazda, so I put almost full aereo to avoid losing grip in tight corner.
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Use your telemetry bud. See where your max torque rpm is and your max hp rpm is and make note of it. Have your max torque rpm exiting the corners. That’s the initial lay you in the seat. And let the max hp rpm keep pulling down the straightaway until you need to apply the brakes. So max hp rpm just before you need to apply the brakes. Space your gear changes to not go lower than max torque rpm, if your cars engine makes lots of high rpm horsepower then keep the gear changes close to max hp rpm. Still confused message me on Xbox blackcell567 I’ll show ya.
As has been said the diff and rear aero will be causing the launch out of corner.
Try experimenting with the suspension geo, some cars seem to like it maxed out and see what it’s like softening the rear ARB.
Didn’t see what you had tyres had but have a look at temps to find the sweet spot.
I’ve only driven maybe a handful cars that like 48% brake bias (stats don’t always tell the truth)
Not driven it but use telemetry to see what RPM gives max HP and adjust your final drive ratio and get a good launch gear with an even spread to last. Adjust for power tracks.
Good luck
GreetedDust8 has a tune shared which is stated to be for wet conditions. Might be worth seeing how that compares to your own tune.
I’ve try Forza Europa tune and it working better in acceleration matter but handle worst of my poor tune (I play with a DD Gran Turismo Pro). Guess I really need to experiment with telemetry and different settings but this C9 is really a wreid car compared to others.
Tried my own tune on this. Quite a fun car. Unfortunately my tuning/testing was at Road America and the only MP race I had time for was at Mid Ohio, which are very different courses!
Didn’t qualify at M-O and managed to make my way from 16th to 5th. Frustratingly got spun and lost about 15 seconds just after my pitstop, which cost me a podium. Some kudos to the person who spun me though as, although it was frustrating that they spun me, they waited for me to recover before continuing racing.
From subsequent rivals testing, the Max-Min downforce I used didn’t seem to be ideal for M-O (but was much quicker at Road America). I was 0.5 seconds quicker in rivals at M-O with Max-Max but 1.0 seconds slower at Road America.
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If I accidentally spin someone I wait for them. As I don’t feel I deserve there spot honestly after that. Try so hard to race clean but man, get some door to door action and my hands are shaking and heart racing. Mistakes happen. Ty competitive edge adrenaline rush. 
