just checked, both lower control arms outside measurements are the same..
I think I'll just push theese bushings in, get the arm mounted then I can take more measurements with the ball joint on.. should have done that with the old setup..

 

ok, how's this for an upper control arm ? Is that twist normal ? It seems the same on the other side.. No twist would actually make my problem worse

 

I live next to you in Belgium.
Had the same problem for 2 years. Eventually saw that they once welded the lower control arm bracket in the wrong place. Welded it back where it should be (after comparing with a friends car) and all is good now. If you click on my profile and look at my topics you’ll see a lot of helpfull advice .

 

Your twist in your upper control arm is normal. Again it just needs to be the same on both sides.
You need to find something that is different on one side vs the other.

Dusky has a good idea.
Check this bracket and make sure they both look the same. I don't know which side this one is from but those look like factory spot welds to me.
If they have welds on the outside GM did not do it.
Measure the angle of both of these, or cross measure. Again they should be the same. And this is where the lower control arm mounts....just sayin'....

 

If everything is lined up correctly, the lower ball joints should be in the same spots side to side (you may need to remove the springs and spindles to check this). I'd measure some triangles on either side to make sure the frame is square.

This diagram may help, though it isn't very specific.

 

I am following your thread. I have the exact same problem only on the other side. In my case I just restored the car, tram gauged the frame and had it fully welded. I put a link to my thread below but wanted to ask if you have measured your wheelbase as was suggested to me in my thread. I haven’t had a chance to get into mine yet but am anxious to see what you come up with. I can see how my left hand lower ball joint is behind where it is on the other side. Be curious to see your wheelbase measurement although I guess you have it too far apart now to measure it.

https://www.corvetteforum.com/forums...my-sheets.html

 

yeah too far into it now to measure the wheel base / ball joint reference..

control arm attachment brackets look perfect, factory welds, not bent, measured their angle, both the same, (also measured angle between upper control arm bolts, both side, within 0.5deg)

It might be a while before the next update, since I have both control arms (upper/lower) out, I'll have a friend blast/epoxy paint them, then I'll reassemble and measure. During that time I'll find a moment to measure the frame.

If it's the frame I won't fix it, too expensive/labor intensive for me right now, only thing I would consider would be unwelding the lower control arm bracket and move it slightly to regain alignment. we'll see

 

all right guys, the search continues, the suspension has been remounted and I even actually went for a drive, like previously mentioned I don't believe the suspension built changed anything.
Now back to measurements.
I found measuring the frame is quite difficult to do, I've done some, but more to go.
Meanwhile I focused on the front suspension geometry, I read from forums that the distance between the lower arms bushings bolts heads (circled red bellow) should be 16in or 406 mm front and back, I measured mines at 400mm -15 3/4 in for the front and the rear at 415mm -16 5/16, so 15mm-9/16in difference, that is quite significant if they are supposed to be equal.
I also can't see that the front crossmember would have bent between the 2 control arms frame gussets so as to squeeze 9/16in without showing any signs of deformation, could it be bad factory placement of the gussets ? either that or the gussets was replaced at some point, however the welds definitely look factory.

would someone be so kind to measure the following green and blue measurements ? (taken from bottom of the ball joint to the tiny holes in the frame) please take both sides so we can compare I read 52/66.5cm right side, 54/68cm left side

 

measured the frame squareness.. it's absolutely square, down to the millimiter

 

How did you measure the frame? I will get those green nd blue line measurements for you in a bit as my car is in the air.

 

When I repaired my lower A arm mounts I never did find an answer to what the dimension was supposed to be.
I ended up moving them back to where it looked like they came from, as best as I could, with limited resources.
Mine ended up close to parallel and if I remember correctly it was 16.XXX" and they ended up about 1/8" or 3mm out.
Do not remember if it was wider at the front or rear.

The control arms should be slightly wider than the shafts they pivot on.
When the pivot bolts are tightened it should squeeze the arm tight to the shoulders on the shaft and bottom on the bushing collars.
The arms when held up next to each other should be symmetrical and reversed.

You say that there is a new front clip and the front frame horn is bent.
It does not take all that hard of an impact to move the corner of the car back.
A small movement spread out over a large area is hard to spot.
It was probably moved both vertically and horizontally.
A good frame shop should be able to pull things back to where they should be.

If you are unable to have the frame straightened due to location or cost, do what you can do.
Measure the wheel base.
If you need to move the lower ball joint forward you could try to rotate the a arm mounting position.
A small amount of slotting the shaft mounting holes might move the ball joint more than you think.
Try it with the bolts loose and see how much it can move.
Would more be better or even possible?
Proceed cautiously and think through what you can do safely and if it will be an improvement.

 

I measured squareness from the points circled red in the picture bellow. Measured from 1 point to all others, all results came back with a measuring error of around a millimeter.

Wheelbase is 2610mm (102 3/4 in) driver side, 2593mm (102 1/16 in) passenger side, so 17mm (11/16 in) difference. (matches my previous ball joint to frame figure of 20mm diff.. ball joint sits lower than the wheelbase I measured center to center)
In order to get back 17mm at the ball joint, I would have to move the two pivot shaft front bolts inwards by 9mm.
I estimated the spring/frame gap to be 12mm all round at the moment, it would then move to 7mm which should still be ok.

I think that's my way forward.

 

Ok now you are getting closer. Something is 17 mm off. I guess it could be the control arm but I think it is much more likely to be the frame.

• You should be able to measure some "triangle points" on both control arms to be sure they are the same to double check.
• I am curious how you measured the frame "squareness" and did you triangulate diagonally across the frame using the red spots in the Wilcox diagram as an example? If this car has ever been in an accident, I will almost guarantee it is "tweaked" somewhere. You can only find that with diagonal measurements. They are much better indicator of "squareness" than the front to rear. My collision / frame shop here straightened mine for $300. I would at least check this first and confirm before going any further. If you did diagonal measurements on the frame then I would now repeat those diagonal measurements starting from each of the four lower arm mounting bolts, to the red circles. What I would expect is that only the front horn circle would move back from a bumper hit and it bent at the "S", then the other 3 circle / spots would still be OK. But that would also move your a-arm brackets.
• Your lower a-arm mounting brackets could have been moved / bent / damaged / rewelded incorrectly. Or you could change yours to compensate for the tweaked frame, if that exists. I measure mine for you since mine is readily accessible. The two mounting brackets are not exactly parallel. They are roughly 1/2" wider at the front measured ctr to ctr. In effect moving the lower BJ rearward. Because the mounting bracket is tapered front to rear I found it very difficult to identify center. So I thought this would be an easier measurement for you since your car is assembled. I measured the two closest vertical lips of that a-arm mounting bracket. I found the outside edge of that lip was too rounded off to be accurate so I used the inside edge of the lip which was perfectly flat. I measured from the inside edge of that lip at the very corner. You could put a small straight edge there FWIW. And then just use a straight ruler between the two edges. My front measurement was 13-4/8 inches and the rear one 14-2/8 inches. If you use a retractable tape measure you could "hook" it on that lip I used.

 

You picture in post #19 is the opposite of how the a arm should fit the shaft.
The inboard legs are surprisingly flexible when they are not supported by the shaft.
The a arm legs can be bent just removing and replacing the bushings.
A frontal impact could of shortened that side of the triangle.
If that leg of the a arm is the one at the top of your cad sketch and is slightly compressed.
That could be where at least some of the problem lies.
Try it in you CAD model and see how much that changes where the ball joint ends up.
Check out the a arms again very carefully before you alter the frame.
A different a arm might be the best advice.
Some spacers and concentrated force applied correctly might improve the one you have.

I was measuring from the center of the shaft pivot bolts for parallel.

 

hi Leigh1322, thanks so much for writing this comprehensive reply.
Yes I measured the diagonals.
Measuring the bracket lips like you did I get 13 7/16 front and 14 1/16 back which is awfully close to yours and I'd say within measuring error.
Triangulating the front suspension:
- measurements taken from the 2 front body attachment points
- measured to the middle of the outside face of the bushing bolts and the middle of the down face of the forward sway bar bolt
- bolts reference points were lowered to ground using 2 lasers cross planes, measurements then taken from ground points using laser meter.

In the pic bellow, measurements in brackets are deduced from the CAD model, my own measurements of these are within a mm.
Front of car is to the right

I think we can exclude bad positioning of the brackets, or that part of the frame being bent, yes the front right sway arm bolt (in red) seems to be a bit back but that is part of the secondary front frame, and the control arm points are unaffected so it wouldn't affect geometry.
Next : I will redo frame measurements as my method has got better, I'll also try to measure the control arm itself.

 

ok both lower control arms confirmed to be same dimensions, so no suspected hidden damage there.
The factory 1.6deg rearwards on the passenger control arm positions "by design" the lower ball joint 11mm rearwards already, so when chasing 17mm, that's my biggest contributor, hence I'm not sure at this stage there's anything wrong with my frame/control arms.
Just to recap, the problem I have is too many shims on the back upper control arm bolt (9/16 back, 3/16mm front), and wheel too far back in the well, caster currently 0deg.

This is driving me nuts, I think I'll just rotate the control arm shaft inwards and call it a day.

 

Ok PB
You have done a fabulous job with measuring and even putting it into CAD! Terrific Job.
I feel very badly for you being overseas without having good access to info, so I am trying to help as much as I can. And my frame happens to be completely bare, clean and accessible.

I see your problem, and yes I believe your frame is bent. It is only one half inch. And I know where and the direction. After all you did say it had a new front clip.

I had to label a few measuring points, and double check against my frame to be sure.
Pts C & H are the front sway bar mount bolts, the most rearward bolt. .
Pts A & G are the front lower A-Arm mounting bolts
Pts B & F are the two rearmost lower a-arm mounting bolts
A & E are somewhere exactly in between the first and second body mounting bolts on my frame. (These do not match my frame by 3")


Pts A & B are both out of position by 1/2"
You had the measurement of how far off Pt B is (rear a-arm bolt) on the CAD drawing, and even the direction. It is off by 11 mm (1/2") to the driver side.
You mentioned that Pt C is off by 11mm too far rearward (1/2" again). (Front sway bar bolt) And your CAD drawing and my frame confirmed that.
Several of your diagonals are off by 8mm or so right side to left. especially the ones connected to pts D & E, near the body mounts. They confirm the above.


So here is what I believe happened to your frame:

Most of your measuring was done inside the redbox area above. That rectangle is relatively strong. And most of those measurements are Ok and bear this out.
My frame man said the weak spot in these frames is the green colored "S" bend shown above. In a frontal impact.
I believe that red rectangle area on your car has rotated clockwise due to the accident. One or both of the green S areas are slightly bent.

I am not exactly sure what measuring spot you used around body mount #1 & #2 but it doesn't matter.
To confirm my hypothesis I would measure all the way back to body mount bolt #3 . (To get way past the S bend) The other end could be anything inside of the box. Might as well use the a arm bolts.

You never mentioned what year your car was, but the frames barely vary. Only the way the front bumper bolts on in front, but those are separate brackets and do not affect the frame measurements themselves. Not even the sway bar bolt position changed, from 63-82.

The other thing I would double check, before you decide how to fix this, is a length dimension on the frame vertically, from front to rear. You need to be sure the S bend area has not collapsed somewhat evenly on both sides. I am curious/suspicious because I could not verify where Pts E & D are on my frame. Use the official locating holes in the frame on the diagram, or the 6 body bolt holes. Compare your measurement to the diagram numbers. I could not get things to double check using your CAD drawing. Use the original frame diagram in Post #25.

My frame was tweaked / bent by 1" but it was in an upward direction on the left front corner, probably from falling into a ditch. (Mine got a new front clip too.)

And believe me when I say these things are not really hard to bend, you can put a dent in it with a regular sized ball peen hammer, (or even easier with a floor jack). They are only 0.110" thick steel. It is the fully boxed design that makes them both stiff, and light. But the two weakest areas are the S bend and the upright at the #3 body mount, because they are not straight there.

Good luck!

 

thanks again Leigh, I'll post a longer reply tomorrow, it's late here

point D and E are my forward body mounting points, they do appear on the frame diagram "#1".
my point C is the forward sway bar bolt

I'll do some more measuring tomorrow

 

Well my concern then is that your measurements to pts D & E miss my front #1 body mounts on my frame by a full 3 inches. They go right past it. So keep measuring!

 

I believe that leigh1322 has provided an excellent assessment of your problem and concur with his diagnosis.

However I still think your pictures show damage to the a arm.
The picture in post #19 demonstrates this.
The gap should not be in the red circle.
It should be where the red arrow is and it should be larger than shown.
The a arm is meant to be compressed when the pivot bolts are tightened.
The legs of the a arm are easily damaged in a collision or when the bushings are replaced.
The C channel of the arm should be square and parallel.
They should not be skinnier or fatter in spots.
Is there a bow in the arm between the bushing and the ball joint?

In post #32 lengthen the dashed green line to the right of 17mm.
It would not have to be much longer to move the ball joint to the red line.
This could easily be at least part of the problem.