From what I have read here about tall spindles/ big brakes/ aftermarket spindles, I have a question. But first of course, the background:

There are those who say that the stock spindle is best because of the correct geometry having been worked out by design engineers before production of the parts in question.

There are those who say that using the tall spindle is better, even though the steering arm location is different, because of the improved upper a-arm angle and improved roll center location.

My question is this: What would the optimum roll center location be?
Before answering that, here are a couple of things to consider:
</font> Is the tall spindle tall enough?</font> Is it TOO tall?</font> Is the stock steering arm in the correct location?</font> How is the lower a-arm angle in all this? Still level?</font>
As I understand it, once the roll center is close, the roll-couple comes more into the picture, closely followed by roll-couple distribution (front-rear). All this has me wondering if the rear needs something too. Panhard bars make the ride harsh and bind up bushed suspensions, Watts links are complicated. I don't know of any other ways to fiddle with the rear roll-center. Also, I don't know how to figure roll center height on a 4-link.

So anyhow, Where would the suspension points be on your "Dream Spindle" and above all, WHY?

Show your work :D
You may begin when the second hand reaches the top of the minute.
Sorry, I started sounding like a teacher causing an essay there for a second :D

K

Bringin it back to the top....

Ok I'll bit first. I can't really give you a good answer at this time, because I am at the newbie stage of this stuff. I really need to review my chassis design book before I could give a good answer.

I would think to answer your question properly you should ask what should the suspension do and then design the components to achieve that goal. For example, determine what you want for bump steer, camber gain, roll center, etc. And then you can say yes X spindle will do this and Y spindle will do that. Then you can determine if a custom X/Y spindle is needed or pratical to build. Or if the X or Y spindle is close enough.

:confused: Did I just answer your question with a question? :confused:

I would suggest that you look at similar chassis designs (unequal length double A-arm) that are designed for performance. The C-4 vette front suspension components are popular right now and are used on custom subframes for first genration Camaros. If you could find out the charteristics of this suspension maybe you could then apply it to the stock A-body setup. (camber/caster gain, bump steer, RC, scrub radius etc.)

Sorry I can't at this point give you an educated opinion on the proper spindle design for our cars. I could give you some guesses but that is all that they would be.

I hope to continue to research this myself, but my time line is pretty long at this point. Let me know what I can do too help.

That's good, more questions make one think.

All I'm looking to do at this point is network the thinking about the spindles so that we can have a more definitive answer than "These work and those don't"

I'm also doing some custom spindle work on my own car, so I'm hoping to get some more intelligent answers than what I can give myself.

Thanks for being the first to bite, RJ

K

I suggest making the steering arm the same length as stock (5.75 inches) so that the turning radius won't be affected. Make the height of the end of the steering arm a little lower than stock to compensate for increased caster, or leave the end in the same position as stock so that an adjustable bumpsteer kit can be used to adjust bumpsteer as necessary.

Bruce Tester

First...the tall spindle is just that...a tall spindle...the geometry is different, so the steering arm has to be in a different location than stock. There is also the question of if the ackerman has been changed. Full Akerman is from a purely geometric stand-point the best solution for cornering (there are other steering solutions that do a better job, but are more complex). However, cornering ability is often increased by utilizing some amount of over-Akerman. This is due to the increased slip-angle at the tire-road interface. In effect it helps the tire heat-up quicker in the corners.
For roll center...there are not cut answers. Lower roll centers are desireable, but if the roll center is too far away from the center of gravity of the vehicle it can cause excessive roll. Basically the design intent is to keep both tire contact patches at their maximum (as the car rolls and the suspension articulates...both tires are true to the road...again some degree of camber accounts for deflections in the rubber and the tire slip-angle).
A parallel arm 4-link basically has the roll center at road height. If you are talking about a 4-link like in our Chevelles...then I would have to show you a diagram...basically you have to draw a top view and a side view and translate the intersection points into the side view.
One interesting note is that the fix for stopping 'Hop' in the rear-end, by raising the upper trailing arm on the axle side, actually raises the roll center.

I guess then the thing to do is to figure out where the steering pivot point would need to be for the A-body suspension using the "tall" spindle configuration. Doesn't sound too hard if you have enough jackstands smile.gif

I wonder just how much of the bump and ackerman oddities of the tall spindle conversions are caused by the spindle height. My spider senses tell me not much, but they have been proven wrong before.

I think first I will see just what bump does with tall height and stock steering arm location, then go from there.

Thanks guys

K

From my experence tall spindle's stock steering mtg. = bump steer!! I moved the mtg. up 1 1/2" and it helped but, I think that now I need to raise the upper a-arm mounting around 2". The tall spindle's will help if we can just get the engineering correct. We hope to get it right on my sons car only time will tell.