Fabricated A-Body spindle ideas and discussion

Yes, your trends with taller spindles and higher ball joints raising roll centers is correct and consistent with my experience as well.

I would be interested in hearing Peter's feedback as he uses the F body spindle with a tall ball joint to raise the roll center, thus shortening the moment lever arm and reducing lateral leverage on the car. This also has the benefit of requiring less negative camber to compensate for the body roll and it creates a more equal roll between front and rear. Some anecdotal evidence on these changes would be nice to hear.

The rear roll center height is found at the mid-way point between the center of the axle and the imaginary line drawn through the spring eyes. So with a high arch drag race spring, the roll center height is below the spring eye plane. On something like a zero arch oval track spring, the roll center height is going to be above the spring eye plane.

So, by raising the front roll center, you are shortening the moment lever arm. Conversely, you could lower the center of gravity height, but that's much harder to do. Most old timers I've spoken to tended to estimate it as roughly camshaft height and just on the interior side of the firewall on a mostly stock, street going car. The oval track cars I was familiar with, this location was 2.5-3 feet back and lowered to a few inches above the trans tunnel.

Finding the exact center of gravity height is a major pain in the butt. Most of the things I've read say it requires four corner scales and the ability to raise the rear about two feet and the ability to put the scales back under the tires at that height. After some geometric trig, you can figure the exact COG of the car. I wish it was easier because I would have liked to do some before and after comparisons on my car to capture changes after a few mods.

FWIW, the very popular Howe spindles used in many oval track classes are only a 1" drop with 10* SAI. You then use a slotted upper control arm mount to move the inner pivot up and down to alter roll center location and different length arms or shims to adjust camber gain.

One reason we didn't go too low on front roll center was to reduce static negative camber and reduce the require spring rates to resist roll. We could then step up sway bar rates and still have some suspension travel for the nasty bump entering turn 3. I'd guess a street car would appreciate a similar set-up.