Trying to battle dat understeer

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So, this morning I got to thinking as to why the #1 Ferrari 641 released recently has so much damn understeer all over the board (going into corners, apexing corners and coming out on-throttle corners). Wasn’t sure if it was my driving so I gave myself a good 25 laps to correct my driving style. STM & TCS off, regular steering and control deadzones set to 0-100. Nothing really changed, but I learnt to compensate for the lack of turn-in response which inevitably caught me faster lap times but I’m still atleast 2-3 seconds short of the top of the leaderboard.

So, I got to fiddling with some of the tuning settings. Springs, ARBs, downforce, damping, camber, toe… While front toe helped to a degree, 0.1-0.2 was all the car would handle without the steering becoming too touchy, and even then, it wasn’t a fix for the understeer, more of a bandaid. Strangely though, what has helped the most (with no compromise to stability) seemed to be differential locking rates… The higher the decel, the better the car would turn turing the apex of the corner, I can only assume this is due to “lift-off” understeer. +0.1 front toe and 60% locking decel rating has got me a second faster, now I’m only one second off the top of the leaderboard (bare in mind this is a relatively new car, dare say it’ll be cracking 52’s on the alps once some people really put some time to it).

Now I’ve got the car apexing and leaving corners flawlessly due to some time spent fiddling with the diff locking rates, but I still have a great deal of understeer going into corners. This can be before braking, after braking, before accelerating, after accelerating, just anywhere near the beginning of a turn, my initial inputs into the controller just seem to go unnoticed. Anybody have any suggestions as to what it is that causes the cars nose to go whereever it likes, disregard what the tyres are doing?

I know this has been posted a thousand times, but most often people aren’t posting enough information about their issue, and the problem goes unresolved. Hopefully I’ve given enough information for somebody to give me a hand.

TLDR; Understeer entering corner in 1990 F1 car. Diff rates have helped apexing and leaving a corner, but still struggling to find how to make the front end more responsive coming into a turn.

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I thought this car ran ok with stock setting, i made some adjustments to the bump as it is to hight in relation to the rebound, car does have some understeer as its the nature of it specially at mid to exit corner as far as entry i did have plenty of speed but lost a lot of time at mid to exit. To combat it eccel has to be high (80/85) to about (20/30)decc. It worked fantastic for me at Monza full Alt. Where i was able to place it at #13 hardcore and has plenty more. Good luck!

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It was 100% placebo affect that adjusting the decel helped with your on throttle mid corner and corner exit understeer. It is however the reason you are complaining to lack of responsiveness in the early part of the corner. I am guessing lowering the decel made the car more stable, which gave you more confidence throughout the track which is why your lap times dropped. Or you started gretting used to the higher speeds of an f1 car if you came from something slower.

Lower decel % more off throttle oversteer
Higher decel % more off throttle understeer

^ you are doing it backwards which is why you are not getting the results you intended.

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Can you explain to me why the differential settings would be backwards on this mid engine, rear differential car.
My experience has been that, on rear differentials, increasing the accel setting increases oversteer and decreasing the accel setting decreases oversteer. Increasing the decel setting increases lift throttle oversteer and decreasing decel setting decreases lift throttle oversteer.
Is there a reason why this car is different? What makes this theory reversed in this car? Is it because it’s an open wheel car? You have me confused now, LOL. I’ve never had trouble with tuning, but I have not yet tuned one of the open wheel cars.

Peace

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Though I have not run it a lot of times, I personally have not run into this issue, and, (as stated by PTG W4RLOCK) I also made just several changes to the stock tune. Max/Min Aero and Diff around 85/10. I think I ran it with 16" rims. Will test it again to see.

**UPDATE = Took it for a quick spin at Silverstone and managed just fine (for my driving style) with the current 85/10 settings. A very minor slight oversteer. Could maybe go to a 85-to-95 on Accel and Decel probably in the 12-14 range if fine tuning required.

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if your talking about a r class + its got to be aero. Try having the rear wing half and the front max as a rough general guide.

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Music to my ears, how lovely is that V12 sound…

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So, high aerodynamic grip reverses the physics? I guess I need to go tune this car and learn more first hand. I thought perhaps there was something built into the open wheel cars or maybe their suspension that attributed to what he was saying.
I’ve tuned a lot of the “race cars” R, S, X class over the last 10 years, and always used the rule about differential that I stated above.
I like to build a little lift throttle oversteer into my tunes. That is what best suits my driving style, which is not topping the leaderboards, but is competitive and usually around top 1%. I usually run the higher differential setting in middle classes C, B, A and begin to lower them in S and R. Lower differential settings can really tame the S and X Class cars, and higher differential settings seem to get better performance out of the mid to lower classes. In my opinion.
Not a lot, just enough to manage if I need to lift during a turn due to something going on in front of me ( i prefer to be cautious and avoid unnecessary contact). So, I play with the differential setting a lot.
This is as good a reason as any to dig into an open wheeler.

Peace

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No decel works the way i explained for all cars. Lower number decel = more off throttle oversteer higher number decel = less off throttle oversteer. Go take any car preferably rwd as its more pronounced and try the same corner with the number at 0 and 100 and report back.

1 Like
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I just tried the Ferrari 641 like you said. I started with the decel at 0, and the result was just as I expected. At 0 the car had no lift throttle oversteer. At 100, the lift throttle oversteer was present. Since everyone claims this car has an under steer problem, that probably explains why the lift throttle oversteer in not aggressive like with some cars.

I tried it with the Ford Shelby GT350R and got the same results. More decel, more lift throttle oversteer.

In the game, the description for tuning the differential reads: “the differential allows the tires on each side of the car to turn at different rates, since the inside tire travels a shorter distance around a turn than the outside tire. A Limited-slip differential locks at a preset point to limit this difference in rotational speed, providing maximum traction under acceleration and/or deceleration .
The deceleration setting adjusts how much of a difference in wheel rotation is required to lock the differential under acceleration. Increasing the deceleration setting makes the differential lock more quickly under deceleration., but excessive differential licking can impair handling . On rear differentials , decreasing the deceleration setting can REDUCE lift throttle oversteer in rear and awd cars. Reducing the deceleration setting makes the differential lock more slowly.”

This information has always been in the tuning area of every FM game. And it always said the same thing.
So the results I am getting are in line with what FORZA has always told us, and with the way I have tuned my cars since FM2. I didn’t tune in the first Forza.

That’s what there me off with your comment. Apparently, there are other adjustments that contradict or counteract the differential settings. From brakes and aero, to suspension damping and even tire pressure.

But, the general rule is backwards from what you stated.
More decel creates more lift throttle oversteer.

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too much rear wing = understeerty high speed = (after you compermise the balance) oversteery low speed.

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I agree with PTG Baby Cow for most part.

Essentially, The higer the lock is, the more the axel where the lock is will resist turning. For explenation standpoint I’ll use RWD.

When you completly “lock” the differential the tire width comes to play. If the combined grip of the rear tires will overwhelm the grip of front tires, the result is heavy understeer.
How ever if the front tires manage to overwhelm the grip of just one rear tire, which will be inside tire due weight shift, the tire will lose it’s grip, which leads to only outside rear is holding the rear in line,
Assuming you don’t have really high rear downforce the outside tire cannot hold it’s grip, which will cause oversteer. This is why many very cheaply built drift cars have “welded” differential (basicly 100/100 lock) which will aid them to to brake the traction. and even thuogh they lose the rear grip this way, they will still keep gaining forward momentum in same manner as you get on full throttle acceleration, it’s not much, but it’s enough to keep the forward momentum going.

This isn’t simullated on Forza too well, but the effect is there, usually you only notice it when you have very evenly sized tire widths on front/rear

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PTG Baby Cow is 100% right. Start with the decel diff at around 30-35% and lower it from there until you have neutral turning behaviour off-throttle.

If you lower it too much the tail will become unstable, if you have it to high the car will still push wide.

Anecdotally ,I think many players just drive around the need for a properly tuned decel by remaining partially on throttle. Every car should be able to turn smoothly while decelerating.

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Mick i think its actuallt quite the opposite. From testing other people tunes i have found that many people prefer a car that is stable or understeers and would rather completelt coast around a corner than modulate a throttle so they tend to tune the car around having a higher dif setting.

On the opposite end of the spectrum many of the lb tunes have extra power over grip as those near the top of the leaderboard can handle those type of cars so they tend to run a very soft rear to enable getting the power down coming out of a corner, in doing so this inherently creates a car with a tendency to understeer. To offset this they run very low decel to allow the car to rotate and use throttle modulation to control the oversteer from very low differentials.

I think part of the reason for the mosconception that it creates oversteer is because the car is more stable many of the more average players have more confidence to push harder or brake later causing the car to oversteer.

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You may be right mate. We all know how it ‘should’ be done though. There’s nothing worse imo than having the nose persistently push wide when you’re trying to attack an apex or carry speed into a sweeper

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100% decel is simulating a locked differential under deceleration conditions. This effectively means that there is no allowed difference in rotational speed between outside and inside wheel. Because the wheels are tracking different length arcs (geometry) through a turn, they actually want to rotate at different speeds. With a locked diff, one or both of them will typically break grip which passes as oversteer for those who don’t know any better. Basically you are losing traction at the rear. I imagine that this phenomenon is behind your observed results.

With a locked diff, the preferred direction of the end of the car in question is straight. The wheel traveling the shorter arc will naturally resist the direction of turn. A properly set up car will seek to maximize available grip at all times, and that does not include using the diff in ways that will unpredictably break traction on the driven wheels.

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to add to what Mick has said 0% decel the dif doesnt lock, this allows both tyres to turn at whatever speed they want while decelerating. The reason this causes the lift oversteer that I am referring to is the tyres outside tyre has more freedom so as Sir Isaac Newton says an object in motion tends to stay in motion. It is going to try to maintain the same speed, as well as the inside tyre. The momentum from these tyres staying in motion will push the rear of the car outward at a quicker rate than the front unless the front has less grip than the rear in which case the car will pull.

You can however tune however you see fit but unless you have come up with some anomaly, due to the way you tune or drive you and forzas description have it backwards. This is known that this has been backwards for quite a while. Being that you are a veteran and have been around the forums it is pretty well known that forzas descriptions in the tuning menus are pretty bad and known to be wrong.

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Yeah, what I am considering lift throttle oversteer may or may not be lift throttle oversteer.
What I tune for is a slight assist towards the turn when I lift. The car and track determine how much I want. Sometimes if I carry too much speed into a turn, or when the rear end is really loose on acceleration, I can navigate a turn with short bursts of lift.
I have always tuned my cars that way, and it has always worked that way for me. But, maybe that isn’t lift throttle oversteer.
I imagine things get much more precise at your level and speed, and my methods may actually be slowing me down. But for now, they are working for me.
Thanks for your insight. I will have to do a lot more testing to see what I am doing wrong and understand this better.

Peace

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Simple test, is like i said take the car and go to the airfield track in test mode so you can make changes easily, get some speed on the start finish straight and go into the first corner start cornering the long sweeper and keep the steering at full lock with the throttle on then let off throttle. Do this at 0%, 50% and 100%. You should notice that the car wants to rotate the quickest and 0%, and get progressively slower with less turn as it goes up. As you are noticing tho, with the diff 100% the car may snap oversteer because there isnt enough difference between inside and outside and that overcomes rear grip.