Control arm to control arm dimension

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Apr 24, 2012 | 10:10 PM

BBCorv70

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From: Tolland CT

Control arm to control arm dimension

I noticed my upper control arms have a stack of shims on each side, rear end of the crossbar. I know one side has none at the front, the other has one. The car isn't giving me any trouble handling other than maybe being a bit resistant to turning, tracks pretty straight. I'm wondering if the alignment shop set it up with a lot of caster, pulling the upper ball joints back. Could be the springs are sagged, or maybe the crossmember has sagged?

I would like to check the dimension between upper control arm mounting flanges, see if there's any evidence of sagging of the cross member. I find it hard to believe this is a problem but thought I'd check anyway. The Chassis Service manual doesn't provide much detail, this dimension isn't shown. I found a frame dimension drawing on-line for a 79 which had this dimension. Not sure whether it's the same for 70?

Does anybody know what this dimension should be?

I can check the riding height to get an idea of whether the springs are weak.

Last edited by BBCorv70; Apr 25, 2012 at 10:30 AM. Reason: Corrected remark about where shims were placed

Apr 24, 2012 | 11:43 PM

oldalaskaman

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only way to answer most of your questions is to check the alignment specs and then compare them to what is specd' for your car.

Apr 25, 2012 | 08:03 AM

70BBvert

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From: Massapequa Park NY

IIRC it's 23 7/8" inside to inside, I can check for sure tonight

Jim

Last edited by 70BBvert; Apr 25, 2012 at 08:32 AM.

Apr 25, 2012 | 10:27 AM

BBCorv70

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From: Tolland CT

Here is a diagram for a 79 Corvette, only one I found with the dimension of interest, identified as 'A'. This diagram specs 26 3/8 inches. I fashioned a makeshift plumbob, measured 26 1/4 inches. If this dimension is shared between 70 and 79, seems pretty close. I'd guess the shop may have been maxing out the caster based on the pattern of shims.

Apr 25, 2012 | 11:23 AM

69 Chevy

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From: Lehigh county Pennsylvania

You're not doing yourself a favor by having the alignment shop set your car to the bias-ply tire settings of 1970 if you're now running radial tires of possibly a different, meaning wider, size. VB&P and Guildstrand websites give recommendations for 4 wheel alignment based on different driving styles.

My '69 frame drawing does not list that dimension.

Apr 25, 2012 | 11:32 AM

BBCorv70

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From: Tolland CT

I don't know what specs the shop set the alignment to. I had it done a few years ago going through another shop. It seems they were going for a lot of caster, keep the car tracking straight with the trade off of having it more resistant to turning. For now it's more a matter of curiousity than a problem.

Thanks for the tip on the updated alignment specs. I am running much wider tires than the originals, radials as well.