Thread: B13 with Progress rear sway, twitchy. Advice.

I completely wrote the opposite of what I meant. What I mean is when the arm is parallel to the ground the static negative camber will be greatest.

The reason I would assume this is because if you look at the motion arc of the lower parallel arms, the point that would have the bottom of the hub pushed out the farthest, giving negative camber (what I meant by "largest") is the point the arms are parallel to the ground.



Still wrong?

Dudeman

Oh my. I've gotten my static/dynamic labels mixed up...

I think you were right to begin with, and are still right.
(I'm not used to thinking about our rear suspension's behavior when the links go "above" parallel to the ground.)

To put it simplest, before my car looked like this:

I I

After I raised the rear, it looked like this:

\ /

(Not that extreme, but just to illustrate the point.)

Significantly different caster will cause some really unstable handling the faster you go. Combine that with significantly different toe-in and you've got a mess.

Your car FL wheel stuck out further forward than the right, but also was more upright (less camber). So for camber imagine this (exaggerated) relationship viewing the car from the front:

| \

then consider the more upright wheel sits further forward. But for now screw the camber, you need to even out the caster. It's not officially "adjustable" so one of two things - there's enough slop that you could loose the bolts at the bottom enough to move it back, or b) something on the short caster side is bent. LCA's can bend with a good frontal impact, you may not even see it on the car. I'd want to match the short side (less caster) with the long side, more stable at speed and better turn in.

Either way this will cause some unpredictable handling at both ends of the car. And yes, changes in ride height will change your alignment, especially the toe-in settings. Changing the camber up front will mess up the toe, it's all related.

I have a good example of a before/after alignment that was sort of screwy with my last new set of Progress CO's, the rear had positive camber before alignment and slight toe-out, worst of both worlds. I'll see if I can find that alignment because it really demonstrates before/after and I tracked the car all day in NHMS with a really funky alignment, then came back with it aligned right, I can def speak to the differences.


So you have a wheel that will break loose sooner when loaded, usually RH turns, but worse, the pass rear end of the car will be lighter compared to the driver's side in a LH turn. That kind of difference throws the whole car out of balance. My guess is under hard braking it would also pull toward the ditch.

Which direction does the a) turn-in feel better b) the rear end feel more sketchy? I doubt it's the same both ways if you really think back to where it felt loose esp on VIR. I am guessing RH turns for worse sketchy rear end, but there I go answering my own question

An old trick that I used when I did alignments at the bodyshop (post crash fixes). If your caster is jacked like yours is. If your alignment guy is damn good, he can loosen the bolts that mount the front subframe to the chassis while its on the the alignment machine and using various methods it might put it back in spec. You are simply moving the entire front suspension relative to the centerline of the chassis. Ive used frame machines, ratchet type come alongs and hydraulic porta powers, I wasnt tweaking the frame just moving the subframe around a bit. many times it got me right where I wanted to be.

Yep, working with a really good guy here we were able to get the negative camber in the rear even and better than it should be considering it's "non-adjustable". A good guy can go a long ways with leverage and just moving things around a little. We did both my B13's and they handle spectacularly well, great balance and very good control. I can't however imagine doing either one w/o the GC plates, those are so essential to get the front they way you want it.

Did you get a chance to check your spring rates? That would be a big help. Yes you can easily get a light rear end and yes you can get snap oversteer, but for so many reasons from rapid throttle lift to under-spec front spring rates, alignment, sway, brake balance and braking modulation, it's a very long list. Just remember that chassis stiffening measures are first priority like a good LCA brace up front and the rear RTSB was a big help on my car.

Besides some lousy driving on cold tires, this is a great example of pushing the balance of the car way outside reasonable limits, those are 350 lbs-in springs buried up front. I run 450's today, but honestly here it's the recovery from a spin and ham-fisting the slalom that followed. Came back at it at way too sharp of an angle because it was a long course and was either going to make the gate or take down the cone so I wouldn't get the OC...fast course, too. I made a lot of changes in 2009 and the car is much better for the track or autocross than it was here on a cold CT March day...

Protest! You don't have numbers on the side of the car! just messin.

If you don't already know who the best alignment guy in town is ask other autocrossers. They WILL know.

Guilty as charged First autox last season. Later I just left my autocross class, track TT class numbers on all season, much easier, even if it gets a few strange looks driving around.