hi everyone, got problems with my front alignemt, I knew it might not be fixable before going to the alignment shop but went anyway, to see what they could do with it, here is what it came out with (in degrees) :
- Camber L/-0.76 R/-0.77
- Caster L/1.86 R/-0.21

So Camber is not the issue, but I can't get the right caster in spec.
What do I see wrong :
- too many shims on the back bolt, about 3/4" where there's only a small one in the front
- wheel straight I can put 2 fingers between the back of the tire and the fender, I can put 5 in front of the tire/fender, that tells me the wheel is not centered in its weel, ok it could be body to frame alignment issues, but that is secondary for now, I need to get the proper alignment first then I'll see where it sits in the weel. If I were to adjust the Caster to be correct it would need the front ball joint to move even more backwards, moving the wheel even more backwards in the arch.

The fact that we can't get caster in spec and that I already have so many shims on the back bolt tells me I'm trying to chase a bottom ball joint that sits too far back for some reason.
So obvious would be "it hit a curb and that bent something backwards"
I managed to convince myself that the bottom a-arm pivot bar was bent, so I've ordered all the stuff and went for disassembly.. I can't see anything bent or out of shape..(looking at that MF of a bar I'm sure a lot of other things would bend before that) no wrinkling anywhere on the frame.. bushings were good (car was completely rebuilt in 2006, part of the rebuilt was a full front end fiberglass.. yeah I know how that sounds but show me where it's bent).
Also, front suspension stop bumpers have been cut down, so I guess this car might have been raced at some point.. gosh what were they thinking

Bringing the car to a body shop and have the chassis properly measured would cost around 2k where I live, a bit over what I think is reasonable to spend..
Any ideas what to look for next ? Anything I can measure myself to try identifying where is the culprit ?

I'll rebuild the lower a-arm with new pivot bar/bushings/ball joint, we'll see where that brings us, but given that the removed pieces looked good with no play/sign of wear I'm not optimistic it'll get better..
Really appreciate your help guys

 

Shims on the back nut gives positive Caster even though yours is still out. This would be where a Offset upper Control Arm Shaft comes into play on the offending side , of course this is providing the front suspension is all in good shape

 

look up the frame measurements and see if your frame is collapsing in. Sometimes it can be corrected with something as simple as a spreader bar. I'll see if I can find the measurements...

 

Sounds like you may have a bent lower control arm. Measure each lower ball joint to an equal spot on the frame on each side. Numbers should be very close.

 

http://repairs.willcoxcorvette.com/1...mension-chart/

this one has frame dimensions between the rails on the 79 sheet which is the same if i remember correctly. I had one for ealier years saved but cant find it
https://www.digitalcorvettes.com/thr...e-specs.87024/

 

First post states cannt get Left Caster in spec.
Is that a typo, Right side is out of spec.

 

A stack of shims on rear upper A arm stud is normal. camber is also excessive. should really be below -.5, closer to 0 on a street driven car would be better. looks to me like a spreader bar is going to be needed.

 

Can you post some photos?

Positive caster is what you want. It will make the car feel more planted on the highway. If the wheel is too far back in the wheel well, I'd look for a bent lower control arm, or bent mount, as @Jeff78 said.

I use SPC adjustable upper control arms, and you can really dial in a LOT of caster with them, but your problem is that the lower ball joint is to far back (aft).

 

Yeah if that is negative caster -.21 caster (forward tilted spindle) you have something really off. The right side should be at pos 1.8 or so like the left. So you are 2.0 degrees off from where you need to be. With that 3/4" shim stack yes you should be into positive caster. A 1/4" ball joint movement should give you about 1.5 degrees caster, so you are about double that from where it needs to be. So something is 1/2" off.
Triangulate a bunch of random measurements on the bottom. Frame mounting holes to a-arm bolt positions, and ditto to lower ball joint. At an angle across the frame. The important thing is that both sides match (within 1/16") Something is around 1/2" off and it should not be too hard to find, tape measure is all you need.

BTW: I had my frame straightened 1 " for $300. $2k is ridiculous to just "check" it.

Here's a pic of the upper a-arm "tower" measurement that sometimes sags and a spreader bar can fix. 26-3/8"

 

thanks for the replies.. (bear in mind I'm probably 10hrs ahead in the timezone world, so can't react quickly to your posts):

sure I thought about this but this would place my weel even further back in the arch, it's already touching the rocker panel every now and then, so while this could be a band aid to get the numbers correct it won't be practical.. also thought of adjustable a-arms but they are only for the upper a-arm.

I checked that, figured I was 12mm collapsed in, I put a spreader bar and got 6mm back so I'm now just 6mm out of spec (what variation exist on that spec out of factory ?) but given I can get Camber in spec I don't think this is my problem.

I hope this would be true as otherwise the problem lies in my frame.. I can't see any deformations although it would be nice to compare to a new control arm.. Is there any drawing out there that would detail its geometry so I can measure it ?

thanks I'll keep that in mind.. they're not very detailled when it comes to front train geometry though, but I guess it could be an quick check to rule out big problems.

thanks, corrected

/rant-on/ yeah, here in France, this is not the country of "yes we can do it, let's figure it out" it's more how much extra a business has to charge extra to keep paying its heavy employer tax, 35hr week employees.. /rant-off/ I'll try to exhaust all other easier scenarios such as bent control arm before I get to that..

Pictures:
Please forgive the gold.. it was the only colour in stock..it will be replaced at some point, also the piece of string is holding the caliper on the right where I removed the spindle/lower control arm..


You can see the control arm shafts are not the same.. the lower/new one has a bit smaller machined end on the right.. my car is 69, but is there any differences through the years ? Also the new shaft middle (black) portion extends couple mm's more on each side..

Can't see any obvious sign of damage..

 

what would a bent frame/control arm look like after hitting the wheel on something.. curb/front impact/whatever.. is there any usual weak spots I could check for signs ? Where does it normaly fails

 

ok I think I might have found some clues pointing towards a frame distortion due to front right impact..
First pic is taken from under the radiator looking at the forward frame extension


This is looking from under the engine towards the spring bucket, the bolt at the top is the rear control arm shaft bolt


Now from the right side looking in.. the green indent might be normal for the rubber stop.. its bend might have increased in the hit, the bend in the red circle is not there on the other side..


Comments welcome

 

 

that's just a bit of shadow.. I just looked again.. it's not a crack, the left plate goes up vertical on the crossmember where it is welded

 

OK France I understand now.

So I see what you are getting at. It looks like evidence of an old front impact. If right side that could push the lower control arm back a bit.
My frame is currently vertical so I took a quick picture for you.
Measure from the lower control arm mounting bolt to a measuring hole in the frame on the other side. Sort of like the tape measure in my pic.
Then repeat on the opposite side. In an "X" pattern. Same spots. Your measurements should be exact (+/- 1/16")
With a front hit I would expect the frame to bend at the large "S" section and that would move back your lower control arm.
Keep at it you'll figure it out!

Your a-arm looks OK to me.
But to be sure just hold it up to the other one on the other side. If one of them is 1/2" off you'll be able to see it.
Also check that bracket where my tape measure stops, where the lower a-arm bolts to the frame. Sometimes they tear off and get re-welded. It could be on crooked.

If you need any more pictures or measurements let me know. My frame is clean and easily accessible, for now.

I would guess your "bump stop depression" is twice as large as mine. (Tried to get a similar angle).



I also do not like the fact that your two a arm crosshafts are not identical. One of them looks longer​​​​​r as you describe That could possibly move the suspect a arm forward, or backward.

I see you have already removed the a arm bushings. Any pics? Could one of them have been very beat/compressed and caused the a arm to pivot? It would not take much at that location to move the ball joint 1/2". Maybe half that at the bushing. A beat up bushing could also be the whole problem and is a much more common wear item than a bent frame. KISS simple/obvious first!
.

 

Thanks Leigh, that looks awesome, I'll definitely go take some more pics/measurements tomorrow, here are couple quick ones.. for now family calls I'm out of time..

 

My 78 had all the symptoms you describe and it was hard hit on the right front corner. After taking measurements on a good frame I concluded it was the right upper a arm bracket—looked more like a parallelogram than the left side. Ground off the old bracket and welded on a replacement. Included a thick shim both fore and aft for good luck. Went to the alignment shop and it was right on spec. This is not my usual success story but I’m glad it worked😃

 

If it was ever in an accident where the front wheel might have hit a curb the dogleg on the rear of the crossmember at the attachment of the lower control arm could be bent. (See part in Red) Just looking at usually doesn't help as it is bent at strange angles. Using a straight edge and comparing it with the other side is the only easy way to figure it out. I had to do this with mine after I bought it and had alignment issues. Once you can show the alignment people what the issue is they should be

able to make it correct.

 

Please forget my earlier mention about the shafts having different machined ends diameters.. I simply have an inner bushing sleeve still on the shaft duhh

Now when I put the new bushings onto the new shaft and place it so one bushing touches the control arm outside face, on the other side the bushing flat is couple mm's from the arm.. picture :

Is that normal ? Would that be an indication my control arm has bent itself
If normal, How to I go about pressing the bushings as they will bottom the shaft before the control arm? or will the outter sleeve slightly compress the bushing and get flush with the arm ?

 

You could be on to something. Try both shafts on both arms. Both sides should be exactly the same measurement wise.