BMW M3 GT4 car feels broken, can setup fix it?

[blinkngone]

The M3 GT4's default setups are already very US biased, suspension wise.
I wouldn't recommend to unbalance that even more to get rid of issues that are rooted somewhere else.

Yeah, the " issues that are rooted somewhere else" is us and our ability/inability. Not having driven the car since 10/17 it looks as though the car has been improved during the various patches 3 through 7, based on the improvements made in lap times.

[Sankyo]

Edit: I just run it now, I see what you guys mean about power oversteer, it's massive. Higher Power Ramp should take care of it indeed.

Edit2: Nah, put it to 90 degrees, but did not make a noticeable difference.

Hold on. I may have this completely wrong, but 90 degree power ramp means no locking, so full open diff, so maximum power oversteer? IMO you should go for a low power ramp angle to have the rear diff lock early.

[Bealdor]

...90 degree power ramp means no locking...

Correct.

...so full open diff...

Correct.

...so maximum power oversteer?...

Wrong.

Not enough lock can cause some oversteer in certain situations (acceleration out of hairpins for example), but in general it makes the car more stable under hard acceleration because the outside wheel torque is limited by the inside one.

[Sankyo]

Correct.



Correct.



Wrong.

Not enough lock can cause some oversteer in certain situations (acceleration out of hairpins for example), but in general it makes the car more stable under hard acceleration because the outside wheel torque is limited by the inside one.

But a fully locked rear axle will power understeer, or does that also depend on the situation?

At least in my testing last week of the Radical SR8, lower power ramp made the car more stable under power in all cases of accelerating out of corners...

[Bealdor]

A locked diff will normally cause power/snap OVERSTEER because too much torque is transferred to the outside wheel, which will therefore lose traction quickly.
You will get power understeer in low torque situations (accelerating gently) only, but those situations are rare in racing IMO.

[cpcdem]

You could also soften the rear as much as possible (ARB and springs) and then stiffen the front to get the understeer back.

First thing I tried was to lower rear ARB to minimum (0 N/mm), but it didn't make a noticeable difference to me with this car. But minimum rear height did make it a lot easier putting the throttle down on corner exit.

[cpcdem]

Hey, lowering the rear would make the setup similar to the 320 TC which you used to race a while back. Good run with your adjustments.
320 TC ride height.
Attachment 262999

I am still racing it from time to time, I like a lot all cars from Touring Car class (mainly the FWDs)! I had not noticed the 320TC has such a low rear height, guess that explains why it is very good and stable with throttle. I think I'll start experimenting with minimum rear height also in GT3s now

[Bealdor]

First thing I tried was to lower rear ARB to minimum (0 N/mm), but it didn't make a noticeable difference to me with this car. But minimum rear height did make it a lot easier putting the throttle down on corner exit.

The rear ARBs on this car can't make a huge difference (max is 30N/mm).
Which makes adjusting the roll center height on the rear axle (via ride height) a more effective method to change overall car balance.

[rich1e I]

The M3 GT4 was already brought up some time ago and I think the massive oversteer is not setup related. You can try to induce some understeer (It's better to fix the part of the car which is causing trouble, so don't fix the front end if the rear is too loose for instance) but I think it's better to just pick another car. It's too unpredictable to ensure consistency.

[blinkngone]

The M3 GT4 was already brought up some time ago and I think the massive oversteer is not setup related. You can try to induce some understeer (It's better to fix the part of the car which is causing trouble, so don't fix the front end if the rear is too loose for instance) but I think it's better to just pick another car. It's too unpredictable to ensure consistency.

Yeah the BMW has been a difficult car. I think the OP was just surprised at how difficult it was when he ran across it and just wanted to know if there was anything he could do before he moved on. Now cpcdem hadn't driven the BMW before and initially he began changing all the wrong things like the rest of us. When he lowered the rear ride height he cleared the previous WR by 0.281 and the quickest Default by 0.772, the people behind him are not slouches. It is also one of the quickest runs ever by a GT4 car at this track with a 0:57.963. When I checked the setups of those behind him I was like OMG they had changed many parameters and one had lowered the front ride height. The OP can load his setup from PC TT to see if it helps some of his issues.
The change he made from Default Loose was only ride height.