C1 front control arm "droop"

[Al C.]

Re: C1 front control arm "droop"

These springs have been on the car for about 30 years, all I did was sandblast and paint. The entire undercar area was covered in so much grunge that it's hard to tell in my earlier photos what these angles were - and of course, at the time, I didn't know I would want to know!
It is entirely possible that some strange (they LOOK right) springs were installed back when everybody had longer hair and leisure suits.
It won't be the first thing I've had to replace on this car!
... Al '58 #378 245hp NCRS SACC

[John M.]

Re: C1 front control arm "droop"

Al,
If they are the originals they would have the GM part # stamped into the spring at the top end.

Regards, John McGraw

[Joe Pennington]

Re: C1 front control arm "droop"

Al, I have a set of 58 springs stamped 3756540--E. You might want to take one side apart again to check your springs to see if they're original or aftermarket.

[Al C.]

Re: C1 front control arm "droop"

Thanks John & Joe,
I'll pull the spring out and check for # - didn't notice one before, but didn't look closely.
... Al '58 #378 245hp NCRS SACC

[Al C.]

Re: C1 front control arm "droop"

The spring carries 3709497.
Measures 13.5 free length, 4.25 OD, 9.75 turns, wire ~0.535 (may have lost a bit to rust?)
Those look like the same measurements as in Noland's book / Restorer article. And, properly installed, they seemed to be pushing too hard (raising effective ride height at least 2").
But the PN is different than Joe's. I'm going to ask Joe Lucia about the #s.
Thoughts?
... Al '58 #378 245hp NCRS SACC

[John H.]

Re: C1 front control arm "droop"

Al -

Does your car have the engine (and all the rest of the front end parts) in it and is it on its wheels when you measured the "droop"? I don't have my '57 any more, but I remember the stabilizer bar link bushing attachments were at a pretty severe angle, even at measured-correct ride height.

[Tom H.]

Re: C1 front control arm "droop"

Al,

My 62 measures exactly 3/4" difference (9.5" inner, 8.75" outer) sitting on level floor fully assembled.

Springs have not been changed, at least back to 1971 when I bought the car.

Good luck to you.

Tom

[Al C.]

Tom - Thanks for measuring *NM*

[Al C.]

Re: C1 front control arm "droop"

John -
The only things missing up front right now are the hood (what, 20-30#?) and coolant (maybe 10-15#).
At this point I am stymied. Joe Lucia confirmed that my 3909497 springs are original; I verifed that everything was seated properly; yet the springs push the lower arm down 3.5 inches, whereas other fully loaded cars report around 0.75 to 1.5 inches. (actually, pushes the frame & body up, but who's counting) Adding fuel to get to curb weight would add perhaps 60# to the front.
Driving with the upper bumper in compression except when hitting a bump doesn't sound like the smooth ride I remember with my first '58 back when.
Is there any way that these springs could have become stiffer?? When I stand on one (most of my 180#) it deflects about 0.5; that's in the neighborhood of the 300#/in spec. Suggestions to accurately measure their rate?
Doh - Another thought just struck - jackstands at the rear are forward of the axle where the frame gets flat - maybe this is affecting the load distribution more than I expected. Doesn't seem like it would be this dramatic - 2.5 inches at outer pivot is about 1.25 at spring, equiv to about 400# per spring.
... Al '58 #378

[Mike G.]

That could be it

I think the center of gravity is about 56" or 57" forward of the rear axle. In other words, the jackstands there would result in no weight on the front suspension. The place where it sounds like you put your jackstands is about 23" forward of rear axle. That's better than a third of the way between "normal" and "zero weight." Wouldn't that be a kick it that was the problem the whole time?

[Craig S.]

Re: That could be it

Mike - I think you hit the nail on the head....I have seen this when I jack up my 66 also...Craig

[Al C.]

DOH - that IS it

After a night dreaming of floating CGs, I just measured my rear jackstand positions (30" !!! forward of the rear axle). Then I calculated CG poition as 48.5 inches behind front wheels, and the front/rear distribution as 955+1958, versus spec 1529+1383. No wonder the lower arms are headed downhill! With this rear jackstand position, the front end is unloaded by 600 pounds total, or 300 per wheel at 110#/in = 2.7 inches.
I hate it when I'm blinded by smoke in the cockpit ...
Thanks all. ... Al '58 #378 245hp NCRS SACC