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I am now using tubular upper arms, but had previously used the moog problem solver upper shafts slotted 1/4". They seemed beefier than stock at the bolt hole area where I slotted them.
My A-arms are not stock, they are VBP (RIP), but like others have done, I machined them. I think the method remains the same regardless of manufacturer of the A-Arm. I don't have a measurement of how much caster it added, but I can tell you it made a considerable difference when driving it. The same road on my way to work that the car would be very nervous on it now tracks much more true. Steering effort is heavier now (which I prefer).
I slotted mine either .25" or .5" (wrote it down somewhere...) and also machined down the mounting faces, with the front face being machined down a little further. Machining the faces allowed me to more or less exagerate the method of adding more shims in the rear and less in the front, thereby angeling the top ball joint further back. See below images.
Last edited by supervette64; 10-03-2019 at 11:40 AM.
I just measured my spindle height, 12 inches b/j to b/j. So Geometry says a .25" slot would move the a-arm rearward .25" and add 1.2 degrees caster. That's with this change alone. Noticeable. Isn't Corvette Central spec around 2.75 degrees attainable with all stock parts? If you then add 1.2 more, you've got 4 degrees total, which should work pretty well. The offset a-arms could gain you a little more. Their alignment recommendations suggest 4-5 caster even for track use.
I just measured my spindle height, 12 inches b/j to b/j. So Geometry says a .25" slot would move the a-arm rearward .25" and add 1.2 degrees caster. That's with this change alone. Noticeable. Isn't Corvette Central spec around 2.75 degrees attainable with all stock parts? If you then add 1.2 more, you've got 4 degrees total, which should work pretty well. The offset a-arms could gain you a little more. Their alignment recommendations suggest 4-5 caster even for track use.
I drove around with 4.75 for many years which is about the max that nut and shim combo can reliably hold. Even with gussets and everything I had terrific bending forces using 700# front springs with 295 Hoosier R1 road racing slicks on 10X17 front wheels. With my modded slot arms it is now up to 6.5 castor
I slotted mine, too. I'm pretty sure I added or replied to a thread about it with pictures. I did mine in approx 2015 or 2016, and at the time I followed the advice of a forum member named norvalwilhelm.
On a mill I slotted the upper control arm 1/4 inch to the rear. (I have the Borgeson steering box with ride tech brace. ) I followed the guidelines in the back of one of the VBP catalogs and gave the specs to the garage that did the alignment. They said they could get 5 degrees on one wheel, and about 3.5 degrees on the other wheel, so I went with 3.5 degrees. It felt fine.
09-30-2019, 08:24 PM
