himself

Pro photographer is out at our events. I grabbed a bunch of pics of my car and I'm lifiting my inside wheel in lots of corners. The car is a 996 GT3 with revalved OEM Bilsteins on 700#/900# springs.

Question for the set-up gurus: how much lifting is too much? Should I drop to a lower spring rate and/or send the shocks back to redo the rebound? It looks like it might be too slow.







[2 images in sequence]



Note the flying cone!

-td

certz

I am pretty interested in the experts thoughts (calling Larry Herman, VR and I am sure others) but a couple of thoughts:

You are running Michelin slicks (correct?) so I assume you have loads of grip.
The pictures, were these from high, low medium, speed corners or some of each?
Are you running stock sway bars and do you have a strut brace?
I do not think the issue is too soft front springs but too soft rears and you probably need beefier sway bars. Of course, you do not want the front/rear spring rate split to get to high so you probably need to go up on spring rates all around.
Lastly, how does the car handle especially between mid corner and track out? Neutral, oversteer. understeer?

Like I said, I am interested in what the experts say...

dotframe

i have no idea but those are awesome pics either way

Veloce Raptor

TD, why do you ask? What is the car doing when this happens? How does it feel? Is it rolling at turn in or flat?

Adam@Autometrics

That is an acceptable amount of wheel lift, especially for Hoosier slicks and even more so if the balance of the car is good. It is not likely to be a rebound issue, as the front bar holds the wheel up. If you feel you must get that wheel on the ground, stiffen the springs and/or soften the front bar.

Veloce Raptor

BTW, the flying cone is awesome. Your doing?

multi21

Donde esta Larry Herman??? Guy has not been seen lately...

bobt993

^^^^^^^^^^^^
He's around. I will wake him up.

chrisc

Whatever, but the pics are great.

winders

It's not that the front anti-sway bar is holding the wheel up. What it does mean is that the front is more roll stiff than the rear. There are a few ways to reduce and possibly eliminate the front wheel lift:

1. Soften the front anti-roll bar.
2. Go to softer springs at the front.
3. Stiffen the rear anti-roll bar.
4. Go to stiffer spring at the rear.

If the car is not exhibiting understeer, if you have the balance where you want it, none of those four options is a going to be what you want. They all reduce understeer or increase oversteer.

It all boils down to roll couple distribution (RCD). RCD is the percentage of the total roll resistance provided by each end of the car. It is usually expressed in terms relative to the front suspension. 60 percent RCD means that 60 percent of the roll resistance is provided by the front suspension.

Sometimes, to get the chassis balance you want, the RCD will be imbalanced enough to cause one end of the car to lift a tire off the ground in hard cornering. This could mean there is an inherent imbalance in car configuration. For example, it could mean the rear tires are not wide enough to match the grip provided by the front tires.

Scott

Matt Romanowski

Then what is?

Veloce Raptor

I am not sure he needs to. Which is why I asked what the car was doing when it was lifting a wheel. On this particular track (MSR Cresson) many cars, especially 911's, exhibit this. Heck, even my M3 exhibits this on some corners there when I am really hauling the mail. But you wouldn't know it from inside the car, since I (and I suspect TD) am steering with the rear tires...

winders

A tire in the air cannot provide any traction. Once a tire is in the air, the axle at the opposite end of the car must deal with all the load transfer. Neither of these is a good thing.

You can't always eliminate wheel lifting, but it is best to eliminate it if you can.

Scott

Veloce Raptor

Well, because of the camber of the track & driving the rear tires, there is no traction to be had, really, from that tire anyway in these corners. Again, that is why I really need to know whether the car is hooked up or not to determine whether he needs to even worry about this. My gut says he does not...

Astroman

OT, but is your entire car wrapped in that carbon vinyl (as seen in your avatar)? It looks cool! What is the original color of your car?