MatthewMiller

Has anyone ever seen offset upper control arm cross shafts offered for C4s? I see that Global West has them for C2/3 cars (see pic below), but not for C4s. I'm trying to work in some extra negative camber range from the upper arm while retaining the stock control arms. I already have offset lower control arm bushings installed.

WVZR-1

Since the early Corvette and most others had 'captive metal clad' bushings. steel shaft and steel control arms, the shaft replacement wasn't much of an issue if you wanted to modify it. Shaft kit and bushings of your choice even possible. Aluminum shafts, aluminum fabricated control arms changed all of that. Understanding that many (more than likely reported' demolish control arms attempting to remove the shafts and do bushings) I believe it's totally understandable. Had metal clad bushings ever been offered for the C4 I imagine you would likely have seen them.

drcook

MM,

is there a particular reason you are wanting to stay with the stock control arms ?

for future reference,

there are these, but they are adjustable control arms

https://www.spcalignment.com/compone...article?id=369

MatthewMiller

Yes, NCCC Group 3 regs probably forbid using other arms, although I'm waiting on a final ruling (hopefully I will get that tomorrow night). Otherwise, the SPC arms, which would be the obvious and super-easy solution. The aftermarket arms are completely legal in SCCA's CAM class, but I want to try to stay legal for the NCCC class also if possible.

drcook

S of a B*tch I just stumbled into another one of the hidden key combinations that either Google or this forum has and erased everything I had just typed out.

So here goes again. I would suspect that the OEM ones are forgings, which would impart strength. Other than weight, is there a reason that they have to be aluminum ? But of course there is heat treatable aluminum, I did look and you might be able to find a forged blank.

So, back when I was a machinist, tool & die maker, mold maker etc (I did a lot of stuff floating around before landing at a defense shop and working on weaponry) I machined lots of parts with offsets. It actually is really easy. The hardest part of the entire endeavor is going to be choosing the correct material.

Basically you take a piece of rectangular bar stock that is finished to the length, width and height of the current control arms. Locate and drill the through holes.

Then you chuck it up in a 4 jaw chuck and indicate one axis to zero and the other axis to the desired offset off the center line.

Then you simply turn and thread the spindle portions. I would have to look for it being necessary, but on the shafts is a hemispherical raised portion. That could be machined via a "spot facing" type tool that was ground for that radius.

Then if there are any areas needing to be clearanced (profile of the original shafts) you do that once the rest of machining is all done.

The determining factor would be cost, including the spot facing tool if it is needed.

If not needed and the shaft doesn't have to be aluminum, then this all gets much easier.

I stole this picture from another member on the forum so I could put some arrows to reference the hemispherical parts.

This all depends on the direction the offset needs to go, but it isn't hard to do.

Aardwolf

I cut down the conical spacers and that worked well. On one side the control arm was very near to touching the frame ear. It ended up being pretty easy to corner weight and adjust with it close to stock parts.

ChumpVette

Some of the guys racing will Bend the upper cradle where the arm bolts to, to get the offset. Takes a lot of effort to bend that section though.

MatthewMiller

Thanks all for the info so far. Drcook, you are a man with a plan! To answer your question I doubt there's a reason the shaft has to aluminum. However, digging a little further, I realized that an offset shaft is probably also not strictly legal in the class I'm concerned with. I could probably get away with it unnoticed, though, especially if were made of aluminum. That said, I was wondering about an off-the-shelf solution. If it comes to fabbing new shafts, I might do just as well to mill a bit of material off some stock ones to get more caster*. I have a local friend who can probably do that, including addressing that hemispherical spot face. But that's also not strictly legal, I think, and I might not need to resort to that. I'm looking at ways to eek out a bit more range in a couple areas that are legal, including cutting down the conical spacers (Aardwolf, I found the thread where you originally showed how you accomplished that - thanks), and one or two other things that I'll report back on if it works out.

In the best of all possible worlds, I'll get an email Saturday morning from our NCCC governor saying that they approved the use of SPC adjustable arms in Group 3. If so, I'll just use those, because I'm all in for easy.

*I'm kind of looking mainly for more caster, but you can trade camber for caster on these cars, so a gain in adjustment range in either is as good as gain in the other.

MatthewMiller

I forgot to comment on this. I don't know if I have the guts to try this! And it also would be even less legal than the offset or milled shafts.

NASCAR314

Hell, you get any faster,....I'm selling my Vettes and buying a Bass Boat!

MatthewMiller

You weren't supposed to see this!