Is a little inner rear wheel lift ok?

sbrown.nw · sbrown.nw's Garage

Ok, here is how the story goes. 1972 T Targa with 85 Carrera fenders and 16x6&7 Fuchs when I bought her. Put large (22mm front and rear If I remember correctly) adjustable sway bars on her, handled nicely but no autoX events to really push her (note, she has factory sized torsion bars in her but with new upgraded bushings). Then I went to 17x7.5&9 Rota Foxes with new and stickier tires (Kumho XS - love them) but I noticed immediately more understeer. Had the front sway bar tightened and the rear bar loosened. Much more balanced maybe to a touch of oversteer.

So, when I went autoXing in Packwood a few weekends ago with the Oregon and WA clubs (great 2 day event!), I got reports from multiple people that I was getting a little inner rear lift on a couple of quick and abrupt turns. Also, with some follow-up discussion, people said body sway was pretty minimal.

Is that ok or should I loosen up the rear bar some more, since it has a little more room to go in that direction? Also, my 915 trans does not have a LSD but I hope one day to get one in her.

Here are some picts of my car and the event:

http://www.oregonpca.org/events/autocross/ax-results/2009-ax5/ax5-media/

http://www.914world.com/bbs2/index.php?showtopic=98391

TIA a bunch!,

Scott

barney911rs · barney911rs's Garage

Big sway bars and stock torsion bars will lead to you ripping the stock sway bar mounts off the car. That is assuming you have not upgraded those already. You really need to upgrade the torsion bars (will need new shocks to match as well) to some level if you are going to push the car this hard. They are what is used to control the suspension and weight transfer. The sway bars are more for fine tuning what you have.

HarryD · 08-21-2009, 04:37 PM

Scott:

Or you just accept that this happens on occasion:

Stock torsions, 19 mm sways lowered to about 23 1/2 inches at fender wells.

J P Stein · 08-22-2009, 08:53 AM

The man said inner *rear*, Harry. Inner rear lift is totally unacceptable. With an open diff, if your lift the inner rear the unweighted wheel just spins and you go nowhere.....this can hurt acceleration.

I know how to cure this on a 914, but not a 9elben.

175K911 · 08-22-2009, 10:22 AM

You sure it's actually lifting, and not just getting light and spinning?

In tighter 2nd gear turns on the track, I only have a few inches of tread on the inside tire touching the ground, but with the Guard LSD I get plenty of bite to power out. And this is with 23/33 torsions and 25mm Tarett sways:

sbrown.nw · sbrown.nw's Garage

175K911, that sounds like what could be happening.

Scott

HarryD · 08-23-2009, 09:20 PM

Quote:

Originally Posted by J P Stein

The man said inner *rear*, Harry. Inner rear lift is totally unacceptable. With an open diff, if your lift the inner rear the unweighted wheel just spins and you go nowhere.....this can hurt acceleration.

I know how to cure this on a 914, but not a 9elben.

JP:

Good to see your wits have not left you....

Front .. rear... it's almos the same..

Thanks for the correction

Walt Fricke · 08-26-2009, 08:53 PM

How about lifting an OUTSIDE rear wheel?

Walt

cstreit · cstreit's Garage

How does one manage THAT?!

Walt Fricke · 08-27-2009, 11:04 PM

That's what Dick Salem wanted to know. I never found out.

On reflection, maybe it was his buddies gooning him with Photoshop? Though that wasn't suggested at the time.

arrivederci · 08-28-2009, 01:50 PM

Quote:

Originally Posted by cstreit

How does one manage THAT?!

Hard to tell what's going on from a single snapshot, but serious axle hop under power?

enderjetta · enderjetta's Garage

Shadow from fender?

Walt Fricke · 09-01-2009, 11:06 AM

Sun angle sure makes it look like the shadow is from the airborne RR tire.

Serious corner balance issue plus braking could do this? Car very stiff.

Being out of balance not likely with this car owner.

Maybe the topography of this part of the track naturally weighted the RF/LR diagonal (corner balancing is done on a super flat surface, while tracks are anything but)?

Mid-Ohio? Apt to be braking at this point of this corner?

Walt

barney911rs · barney911rs's Garage

Chris knows Mid Ohio better then I do, but that can only be one of two places, and he looks to be in way deeper then I think you would be on the brakes that hard for either one. That is either near the top of the keyhole or the left just past thunder valley. I would vote for the keyhole myself.

The more I look at it, the more I think enderjetta has is right. That's the shadow from the leading edge of the fender. It does make for an interesteing optical illusion.