Car "bouncing" at mid corner. Why?

[shirakawaa]

Hello everybody

Picture this situation:

Big saloon car, LSD equipped front wheel drive. While accelerating, on straights at relatively high speeds (> 150 Km/h), if I steer suddenly the car quickly reacts by moving into the wanted direction. However, as I keep steering, the car feels like "bouncing" for a short while to the opposite direction. Shortly after, as it settles down, it keeps steering to the wanted direction as originally intended.

The question is: What causes the car to "bounce" at mid corner?

The car is a '98 Ford Taurus SHO with all power modes that increase rpm except the racing exhaust (I use a semi-racing instead), with 357 hp @ 6800 rpm.

Chassis weight reduction Stage 3, window weight reduction, ridigity improvement. 1227 Kg.

Tires: comfort soft
LSD: 5/20/5

Suspension settings:
Ride height 0/0
Spring rate 9.2/9.2
Dampers (extension) 6/6
Dampers (compression) 4/5
Anti-roll bars: 1/4
Camber angle (-) 1.2/0.6
Toe angle: 0.00/-0.35

NO driving assists.

 

[Jacob]

Isn't this the game's representation of "Torque Steer"?

http://en.wikipedia.org/wiki/Torque_steering

 

[Goruk]

Maybe too much rear toe or maybe lsd settings...

 

[shirakawaa]

Isn't this the game's representation of "Torque Steer"?

http://en.wikipedia.org/wiki/Torque_steering

I'm not sure. It does the same even when I'm not accelerating.

Maybe too much rear toe or maybe lsd settings...

Removing rear too appears to magnify the problem. LSD settings seem very mild to me already...

 

[Stotty]

Ordinarily, I'd say this was caused by the springs being a bit soft and there being an imbalance between bound and rebound... mainly the rebound being too harsh...

Turn, spring compresses, bound stops it, rebound shoots the shock back up and the momentum unloads too much weight off the front tyre, momentarily causing loss of grip.

But your suspension settings don't look dramatic enough to cause that effect.

 

[shirakawaa]

Even reducing the rebound settings didn't help, unfortunately.
I wonder if it's an instrinsic car problem. I'd really like to make it corner smoothly, not like the current "three-phased" behavior (quick turn-in -> mid-corner "rebound" -> quickish corner exit). However, it's still a large (> 5 meters) sedan.

 

[Stotty]

is it the front that bounces or the whole car... is it understeer or 4 wheel drift?

 

[shirakawaa]

I'd say it's the front. This car has quite some understeer problems which I think I mostly solved if it wasn't for this mid corner bounce. I think this is also the reason why the car will also eat up half its front tires (comfort softs) after just one lap at the Nuerburgring (although it's true that 350+ hp start being too much for a FF car).

On the tire temperature chart, rear tires are always cold (dark blue).

 

[Stotty]

A heavy FWD car with 350 bhp on comfort softs will always be a tyre shredder... but that's realistic.

In real life, 350 bhp would be a big challenge on normal tyres.

Have you tried a small amount of -ve front toe to try and maintain the mid corner grip at the front?

 

[Supermelon]

Ordinarily, I'd say this was caused by the springs being a bit soft and there being an imbalance between bound and rebound... mainly the rebound being too harsh...

Turn, spring compresses, bound stops it, rebound shoots the shock back up and the momentum unloads too much weight off the front tyre, momentarily causing loss of grip.

But your suspension settings don't look dramatic enough to cause that effect.

Personally I think the rebound is set too soft. When the rebound is set stiff, it slows down the decompression of the springs which helps reduce the bouncy feeling.

 

[daveyules]

It's your rear toe-out. If the amount of force over the rear tires is varying throughout the corner, you will experience these transitions from neutral cornering to understeer. Removing the rear toe will resolve this. Unfortunately it also means you will have terminal understeer.

My tune for this car is rather different from what you have listed, so maybe recalibrating your springs and shocks is a good idea.

Cheers

 

[shirakawaa]

A heavy FWD car with 350 bhp on comfort softs will always be a tyre shredder... but that's realistic.

In real life, 350 bhp would be a big challenge on normal tyres.

True, however in this case rear tires remain cold compared to the front ones even by cornering hard and accelerating without applying much throttle. Smaller cars like the Peugeot 106 S16 make the rear tires work too.

Have you tried a small amount of -ve front toe to try and maintain the mid corner grip at the front?

Didn't improve the mid-corner bounciness. Also, I wanted to keep this ideally to 0.00 in order to avoid additional tire wear.

Personally I think the rebound is set too soft. When the rebound is set stiff, it slows down the decompression of the springs which helps reduce the bouncy feeling.

I set rebound to 9 (from 6), didn't help much although it seems there have been some very slight improvements.


This "bounce" can be confirmed visually, aurally (by hearing tire noise) and even by looking at the G meter. When initiating a turn goes above 1.1-1.2 G, then drops to about 0.8 G (when the car "bounces"), then stabilizes at around 1.0 G.

 

[praiano63]

For me when i have this kind of problems, it come from the spring rate balance, with a weight of the front engine like this, i will increase the front spring rate or decrease the rear point by point till the good proportion
After that if not correct, i'll check the front sway bar ,it seems low to me.
Every case is a case and all is combination in this game you have often unlogic settings surprises goods or bads.
But for shure the principal thing you need to resolve this is time and luck also.
The setpoint of online tuning is on my opinion, much more sharp and small than offline. you have to reach it without passing it.

Suspension settings:
Ride height 0/0
Spring rate 9.2/9.2
Dampers (extension) 6/6
Dampers (compression) 4/5
Anti-roll bars: 1/4
Camber angle (-) 1.2/0.6
Toe angle: 0.00/-0.35

 

[shirakawaa]

It's your rear toe-out. If the amount of force over the rear tires is varying throughout the corner, you will experience these transitions from neutral cornering to understeer. Removing the rear toe will resolve this. Unfortunately it also means you will have terminal understeer.

My tune for this car is rather different from what you have listed, so maybe recalibrating your springs and shocks is a good idea.

Cheers

Just tried setting rear toe to 0, and yes, it bounces less. However the car still kinds of "sits" at mid corner, you can feel that it doesn't yet corner smoothly with a more or less constant behavior (no matter whether the car is accelerating or not).

For me when i have this kind of problems, it come from the spring rate balance, with a weight of the front engine like this, i will increase the front spring rate or decrease the rear point by point till the good proportion
After that if not correct, i'll check the front sway bar ,it seems low to me.
Every case is a case and all is combination in this game you have often unlogic settings surprises goods or bads.
But for shure the principal thing you need to resolve this is time and luck also.
The setpoint of online tuning is on my opinion, much more sharp and small than offline. you have to reach it without passing it.

However rear tires are already working very little, if I make the front sway bar harder or the rear springs softer, the car becomes again an understeering brick. Fitting a hard rear sway bar is also kind of a standard thing to do on sporty FF cars in order to reduce understeer.

 

[praiano63]

Look something i've found on the Forza setup bible for FF cars. It's in french but i'll traduce.
Voiture traction LSD SETTINGS
Accélération :
Réglage le plus élevé possible.
Higher as possible
Avec une traction, les accélérations en virage se produisent plus
tôt, un réglage élevé permet d’atteindre le point de corde plus
facilement et de la garder plus aisément (attention aux vibreurs).
With a FF acceleration in a corner hapen earlier, a high value accel setting allow to reach easyly the apex and stay inside the corner (beware rambles)

Décélération :
Le plus faible possible pour contrer l’envie naturelle d’une traction à
sous-virer. Augmenter la valeur si l’arrière décroche trop facilement
dans les phases de décélération.
Lower as possible to avoid the natural tendency of FF cars understeer. Increase this value if the rear "BOUNCE"too easy during deceleration.

 

[shirakawaa]

I found out that with 200 Kg of ballast on the rear (+50) the car handles much better, without throwing me out of trajectory on mid corner, but sliding predictably and linearly instead. The car is probably quite front heavy.

EDIT: I found out here that the weight distribution in stock form in real life is 66:34. This means in GT5 with every weight reduction performed, 809.82 Kg on the front axle, 417.18 Kg on the rear axle.

If adding ballast at +50 ideally adds all the weight on the rear axle, the weight distribution should now be about 57:43.

I find strange though (or better, I don't understand what is that so) that smaller hatchbacks like the Peugeot 106 S16, which in real life have a weight distribution similar to that of the Ford Taurus SHO, in GT5 handle much better and are in general better balanced than that car.

 

[Basilea]

Maybe because they are a lot smaller? So the weight distribution doesn't affect it that much as in a taurus...

 

[zodicus]

and a taurus isnt exsactly a performance car. my guess would be try this

Suspension settings:
Ride height -10/0
Spring rate 11.0/9.0
Dampers (extension) 8/5
Dampers (compression) 4/6
Anti-roll bars: 3/5
Camber angle (-) 1.0/1.0
Toe angle: -0.10/-0.05

see what that dose

 

[shirakawaa]

and a taurus isnt exactly a performance car. my guess would be try this[...]

The weight distribution was the problem. The Taurus SHO is a long, front heavy car. Adding weight to the rear axle and/or decreasing the rear ride height (transfering weight to the rear axle) made the car handle much better and also made rear tires work more efficiently. However online one has to take into account that there's the fuel weight (approx. 75 Kg) sitting somewhere in the back, and therefore to avoid an excessively oversteering (in mid-corner), rear-end heavy car, it's necessary to reduce the rear ballast (or moving it to the front) or increase the rear ride height.

Until now I've never realized how important the weight distribution is to the car handling. And more than ever, I now feel the need to know this information both with the unloaded and loaded car (pilot+fuel). There's also the need for an option to enable fuel and tire depletion offline in practice mode, and an option to select the fuel load before starting a race.

Thinking about it, maybe the car wasn't really "bouncing", it was the front end that was pushing outwards, and tweaking suspension settings was only mitigating this natural tendency due to the weight distribution. Relocating weight to the back (and of course adjusting spring rates and other settings accordingly) makes the rear end do so.

 

[Drewsifer3x]

Yeah good call. That thing has a v8 mounted transversely on the front end. It's neat but awkward at best, especially considering that the base car already had poor handling.

 

[kickin_on]

Yeah good call. That thing has a v8 mounted transversely on the front end. It's neat but awkward at best, especially considering that the base car already had poor handling.

Being the car that it is, I think Drewsifer3x is putting it extremely nicely. All the tuning in the world wont change the fact that its still just a Taurus, and whilst it can be made better, better doesnt mean it sheds all the terrible handling characteritics it inherently has. Nor does being 'better' necessarily have anything to do with being 'good'

Good luck though with getting it as good as is it can get 👍