Okay, just did an alignment, now all the shims are gone from both upper a arms. I understand this means I have cradle sag. Its an 82, btw. How is this corrected? Is this something that I can correct in my garage, or do I need to take it to a frame shop?

 

58 views, no one can tell me anything? Someone has to have dealt with this.

 

there are NO pictures!!!!!!!!!

Post Pictures AGAIN

You will probably get an answer

Good Luck

 

Huh,never heard of cradle sag.Do you trust the alignment shop,are you sure they got it right ?

 

Without pics I can only guess that if your alignment shop removed all the shims from your upper A-arms they were trying to move your camber in the negative direction, which would be opposite of the direction you'd want to go if you had a condition called "cradle sag". If your front crossmember was 'sagging' it would result in your front camber going excessively NEGATIVE which could only be corrected by the addition, not removal, of shims. At this point it sounds like at the very least there is some miscommunication between you and your friendly alignment specialist and at the worst you got taken by an alignment guy that doesn' know what he's doing and/or talking about. If your crossmember ('cradle'?) is indeed "sagging" I would also look elsewhere in the frame for corrosion and fatigue issues. There are spreader bars available that work in similar fashion to a strut brace on a unibody car that can correct this problem, but they're a poor band-aid for a used-up frame...good luck and keep posting as if it does go so far as needing a new frame this forum is probably about the best place to locate one.

 

I do trust the alignment shop, as I was involved in the process. Cradle sag, or collapse, is when the towers that the upper a arms are bolted to move inward over time, decreasing and eventually eliminating the amount of caster and camber adjustment. Spreader bars stop this from happening, as they brace the towers. I didn't expect this to be an issue on an 82 with a small block, but I guess I shouldn't assume, lol. I did find my answer here http://forums.corvetteforum.com/c3-t...alignment.html interesting read, and it appears I need to take it and have the frame stretched back to spec, install a spreader bar to keep it there, and have it realigned. Thanks for the replies

 

Just found more info that states that the measurement between the shock towers at the point where the front bolt of the upper a arm passes thru the tower should be exactly 26 3/8", and mine is about 26 1/8", so the collapse is not severe. I'll know more tomorrow, but I think I can fix this with offset shafts and a spreader bar. I'll post more as my measuring and investigating continues. The fact that we took out all the shims and still couldn't get it "in the green" troubles me. The machine still wanted us to remove more, but there weren't any more to remove. It appears that I have lost 1/4" of space between those towers. Doesn't seem like much, but this is all kinda new to me. Anyone know what the average amount of shims is? It appears that if there is only 1/4" of missing separation between towers, something else must be off, when we started it was wanting me to remove about 13/32 on just one side. I just replaced the bushings, all tie rod ends, all ball joints, rebuilt the ps valve and cylinder, and replaced the front bearings on both wheels, there is no slop in any of the components, the idler looked to have been replaced already, it was solid, no movement. This one has me scratching my head.

 

what are the SAI numbers on the alignment print out ? that is where to look for frame problems. I would also think that 1/4" is not severe enough to cause your problem.my guess would also be the production tolerance for that measurement is plus or minus 1/8" so you are really looking at 1/8" out of spec.I think your problem is something else

 

Are you still running bias-belted OEM tires? And trying to set the alignment at the factory specs?

 

Have you rechecked the other work,it sounds like you've created a problem.
Never tried but is it possible to install the lower A arm shaft flipped ?

 

@dta- No, I didn't get the printout, I should have, that for sure would give me a clue at least where to start looking

@69 Chevy - No, I'm running radials

@Roger- The first time we checked the numbers were very close to what we ended up with after I did all the repairs. I also marked which side of the shaft was against the frame, upper and lower. I guess its possible that someone before me may have installed them incorrectly, tho, that's something to look at. I don't know if the bushings I replaced were original or not, but they sure looked original, lol.

After going back out this morning and looking closer, I have discovered that the passenger front fender is higher than the driver's front. There is definitely more of a gap between the top of the tire and the lip of the fender on the passengers side compared to the drivers side, so I remeasured the distance between the shock towers with fresh eyes. Its not 26 1/8, its 26", so I've lost 3/8, and I'm starting to think that the driver's shock tower has been hit or bent in, since the drivers side of the car is lower by approximately 1 1/16" at the center of the front wheel wells. I do have the springs in both pockets correctly, so I can eliminate springs as the cause. That only leaves the shock towers or frame. I will go back out and verify that the lower a arm shafts are installed correctly, tho, to be thourough. More on this as my investigating continues...

Thanks for all the replies, keep em coming!

 

Just checked, and the lower a arm shafts are not on 180* out, so that isn't the problem

 

Again, if the nominal distance between the towers should be 26 3/8 and yours is 26 1/8 you have a condition that will INCREASE negative camber. Removing all the shims from the upper arms will only make the situation worse. Actually, since you're only 1/4" out you could easily ADD shims and get the camber where you need it to be...

 

On C3's you add shims for negative camber, remove for positive. You may be thinking C4 where it is the opposite.

 

Not sure I'm understanding, but the towers being closer to each other, instead of farther from each other should require less shims shouldn't it? I'm not questioning your knowledge, just trying to understand the dynamics of this front end. As I understand it, if you add shims you are effectively pulling the upper a arm shaft closer to the centerline of the car. Now that my towers are basically a full 3/8" closer to the centerline, that should require less shimming, not more. But then again, I'm very new to this and I may not be understanding it correctly.

 

You are correct Drawmain.

 

OOOOPPPSSS!!! FAIL!!! Sorry 'bout that...I fergot thos shims fit onto the inside of the control arm mounts. Somebody please ignore me...

 

Okay, update, called the body man that did my bodywork last year, told him what was concerning me, he gave me the number to an alignment shop. I called them, started describing the issue, and he finished my sentence for me, lol. He said "Yeah, I must have done a thousand of those fixes on Vettes and other cars over the years, bring in on in, we'll have it done in a day. Your front crossmember has flexed inward taking away your caster and camber adjustment." This guy seems to know exactly what to do, so, I'll drop the car off tomorrow morning. When I get it back I'll follow up here and let y'all know how it all works out. Thanks to everyone for the information and advice

 

One other thing you could check are the lower control arm frame brackets. They could have been knocked loose and welded back in the wrong place.

 

very common, on alot of older cars, my father inlaw does at least 1 a week. (pull the front back to original specs)