Curing the "tank slapper"

[Slurm]

Basically, this is my least favourite handling defect, and the one I find hardest to iron out. Some cars will break traction predictably but once the wheel-spin begins, they destabilise in a terrifying way: Sloppy response to counter-steering and a tendency to veer in the opposite direction as traction is re-gained.

What exactly causes this effect and is there a more technical or common name for it? The NSX-R is a perfect example of a car without this problem, and so far I think the Murcielago is one of the worst I've encountered.

 

[psychot|K]

I dunno forsure, but I think it has to do with grip. Anything with grippy tires will REALLY swing hard once the traction is lost. Then, with countersteer applied, it will gain that large amount of grip again, then swing in the direction of the countersteer.

 

[oppositelock]

Possibly a combination of the following factors:

LSD settings too high or extremely high variance between the three settings. In my experience high settings can cause understeer up to a certain point, after which they can induce snap oversteer. High variance could theoretically cause problems when transitioning between accelerating, coasting and braking as the LSD locks and unlocks.

Insufficient rear toe-in. I run lots of it on all my RWD cars and rear/mid engine AWD cars, often up to a full degree. Really gives the back end that "locked down" feeling. Some people say it causes too much understeer, but I think that's poppycock. The front end grips the same, the back tires are just now more inclined to follow the fronts, imo.

Suspension too soft, particularly the dampers. As the body rocks back and forth it builds a certain inertia that can destabilize the car. It's important to match to suspension to the tires: more grip, stiffer suspension.

 

[BlueShift]

Possibly a combination of the following factors:

LSD settings too high or extremely high variance between the three settings. In my experience high settings can cause understeer up to a certain point, after which they can induce snap oversteer. High variance could theoretically cause problems when transitioning between accelerating, coasting and braking as the LSD locks and unlocks.

Insufficient rear toe-in. I run lots of it on all my RWD cars and rear/mid engine AWD cars, often up to a full degree. Really gives the back end that "locked down" feeling. Some people say it causes too much understeer, but I think that's poppycock. The front end grips the same, the back tires are just now more inclined to follow the fronts, imo.

Suspension too soft, particularly the dampers. As the body rocks back and forth it builds a certain inertia that can destabilize the car. It's important to match to suspension to the tires: more grip, stiffer suspension.

This is one way to tune and cure this.

I'd say rear SR to increase (or front to decrease), initial/accel LSD to decrease, rear aero to increase (or front to decrease).
Last ressort : Rear RH to decrease (or front to increase)
Very very last ressort : toe 0° front / 0.04-0.2° in rear.

What is you camber setting and weigth of your car ? It might be that in fact !

 

[Slurm]

Thanks for the tips guys.

It's a CHaparral I'm working on! So, very short wheelbase and uber torque.

I've just tried some of your suggestions with success so far..

Rear camber up from 0.6 to 1.6 (now equal front and rear) - I believe this helped - the re-gaining of traction at the rear seemed less sudden.

Also loosened the diff: Was running at: i40, a30, d30 - I noticed that the outside rear was lighting up under power. Opened it to i11, a9, d12 as a starting point, for comparison, and now both wheels spin, slides are somewhat more controllable.

I still want to understand the dynamics of this problem better. The best way I could describe it is the car whipping right as it recovers grip from power-oversteer in a left turn, or vice-versa.

This is supposed to be a preliminary set-up, but I've actually set the fastest lap with it completely equal suspension settings at front and rear at the moment:

RH: -10
SR: 18 (of maximum 20)
Damper extensions: 9
"" compressions: 7
AR: 2

Cambers: 1.6
Toes: 0

edit: So after testing on/off for a while, I have this car behaving like a well-mannered go-kart. xD Settings have changed back and forth all over the place but I'm almost happy with it now!