SS gets squirelly under WOT
 

Since the rear has been apart several times recently for the 9 inch conversion with an S trac posi (mechanical) I am trying to get my alignment dialed in again, Hopefully some of the alignment gurus can help me out here.

The SS has Spohn trailing arms and toe rods and BMR bushings on the spindle side of the trailing arm. Hotchkis chassis max brace on subframe and Hotchkis 1" lowering springs.

The car is wiggling (not violently) very tightly back and forth side to side under hard acceleration (WOT all gears), most notably at the strip, but does this on the street too. It only became apparent after the 9 inch conversion and the much faster/aggressive acceleration now.

The old numbers were

Front Left Right
Camber -.8 -1.0
Caster 5.9 5.8
Toe in .09 .11
Total Toe .20 Steer ahead -.01
Rear
Camber -.3 -.4
Toe in .10 .09
Total Toe .18 Thrust angle 0.01
NEW current Numbers -

Front Left Right
Camber -.8 -1.1
Caster 5.8 5.9
Toe In .05 .05
Total Toe .10 Steer ahead 0.00
Rear
Camber -.8 -.8
Toe In .07 .07
Total toe .14 Thrust angle 0.00

Can someone give me some advice for which direction I should go with the numbers? Since the new alignment the car did get better with less wiggling but it still has some movement. I am guessing it wants the rear toe and camber closer to 0? It did pretty well with the rear camber near -.3 or -.4 on the stock diff. I have checked all the subframe bolts and hotchkis attaching points.
I am shooting for a happy medium between aggressive street and drag settings on street tires (Invos), I run the car on the drag strip several times a month but mostly street driving. Sorry for the long winded post. Thanks!

Is the car corner balanced? We had a guy here that was having this problem and he tried everything and nothing worked until he got it corner balanced.

It has not been corner balanced. What all is involved with doing that?

Corner balancing is a good idea after you've changed a lot of your suspension components and ride heights. Find a performance shop with the alignment and scales equipment. Not too dificult or expensive. Think of a table with one leg shorter than the other four. When you tilt the table on the short leg, it carries more weight than the other legs. When you tilt the table away from the shorter leg, the short leg carries little to no weight. This is an overly simple analogy, but you get the idea. It might not cure your problem, but is worth doing anyway.

They put your car on 4 individual scales, one under each wheel, and normally balance the car so the weight distribution is even all around (or whatever you request).

Some will do this with a full tank and you sitting in the car.

Does toe change when the rear suspension is under load?

I'm not sure. Everything is poly bushed now, so deflection or movement should be minimal.

out of curiosity, what did you do with the old diff?

After putting a cam in my car I had the same issue. I had it corner balanced and a new alignment done at the same time and straight as an arrow now. And my car is 3818 lbs with 3/4 of a tank and no driver.

Sold it.

thanks,

good luck finding the source of the "wiggle", i am sure you will.

You should contact Pete at Pedders, he provided me with three options for alignment (street, auto-cross, drag race) His e-mail contact is: PGB@PeddersUSA.com. As for corner balancing, you should definitely have it done and when it is done it should be with you or your weight equivalent in the drivers seat.

Most performance shops will do a corner balance with 200 lbs in the driver's seat and approximately 1/2 tank of gas......unless you tell them otherwise. I've seen guys poor-boy it with inexpensive scales, but they have no way of knowing if the car is completely level.

Any alignment gurus with input? I emailed a few but no responses.