Theory question - given that when you go to the tall spindles, you'd need to pull the upper arm inward a lot with shims, why not go the alternate route and just go with longer lower control arms?

Now, admittedly, I typically don't have a real clue as to what's going on, but it seems like that if you went with 1 or 2 inch longer LCAs, you'd end up with the same net effect - the uppers would be shorter than the lowers so you'd get an improved camber curve (not sure what effect the differing ratios have though), and from what I've read a wider track helps a lot - and this would force one.

You would have to change offsets since you're playing with the track width, and I'm sure that scrub radius might suffer - but I've seen some say it suffers with the shorter upper arms anyway.

I'm sure there's a great reason why everyone is making the uppers shorter and not the lowers longer, but I'm not seeing it.

I would assume that most manufacturers are making shorter uppers because it is an easier part to build than the lowers. With the uppers you have a mount and a ball joint to deal with. The lowers require spring pockets, mounts, ball joints, shock mounts, sway bar mounts, etc. Just economics I would think.

The only down side that I imeadiately see is the tie rods would have to get longer. And I think that is the biggest problem with the Tall spindle bump steer issues. The tie rod is to long, and so making the track wide would only make that even worse.

After saying all of that, I sure that I could be done, it just hasn't yet that I have seen. graemlins/thumbsup.gif

Part of the reason to go to tall spindles is the more agressive negative camber gain on suspension compression which increases grip in corners. This gain is achieved by shortening the upper control arms. As the suspension compresses and the arms rotate upwards, the shorter upper arm pulls the top of the spindle inwards more, which increases negative camber. The shorter the upper arm, the more dramatic the gain of negative camber upon compression. Going to a longer lower arm would also provide this benefit if the stock upper arms were used, as the upper arms are now effectively "shorter" in proportion to the lowers. However this would increase the track width of the front end, requiring longer tie rods. Since the tie rods are now longer, their swept arc throughout their travel is now changed, which would affect bump steer. The longer upper arms would also increase the arm/tire's leverage on the springs and shocks, so stiffer springs and shocks would have to be used to provide the correct road "feel".

That's why the shorter uppers and stock lowers are used-- much simpler!

Troy

I have not studied my suspension yet, or got around to my tall-spindle swap, but heres what I am thinking...

The reason for the shorter arm is because the arm is swing through an arc, and now with the tall spindle, the LCA/balljoint is in the same place, but the upper is raised (1.5 inches?). The position of the upper balljoint is below the upper crossshaft, and therefore when raising the upper BJ, the upper arm is swing through an arc, and closer to level, and therefore increasing the horizontal distance between the croosshaft and BJ. Therefore the horizontal distance needs to be shorter, or the top of the spindle will tilt out initially... The same thing will theoretically happen when the standard-spindle suspension is compressed. as the upper arm swings through an arc, it will cause the top to tilt out. The alignment shims allow this to be compensated for the normal driving conditions (thats why not all cars need the new upper arms).

With the tall spindles, the upper BJ is closer to the height of the upper cross-shaft, and therefore there will be less tilt as the BJ and X-shaft approach the same elevation...

If the tall spindle is 1.5 inches taller (I can't remember the dimensions, but lets ay this is it for this discussion), then the short spindle will tilt the same amount when it is at 1.5 inches of compression (lowered) as the tall one is standard)... In other words, the upper BJ is in the same position relative to the frame...

Yes, lengthening the lowers would cause the same net effect... but now the wheels would sit out farther too... I guess it would still work, but the cost of lower arms is more than uppers...

Sorry it I sound confusing... I can't think of how to describe this without diagrams... Thats even if I am on the right track...

Long hot day! I need a nap smile.gif

Gokou, airrj, thanks for your input.

Originally posted by Gokou:
The shorter the upper arm, the more dramatic the gain of negative camber upon compression. Going to a longer lower arm would not provide this benefitWouldn't it though? It seems like it's the length ratio between the upper and lowers that really affects the camber gain; the change might be less dramatic (since 2 inches shorter on the upper is a larger percentage of the normal length of the upper than 2 inches longer on the lower).

I'd imagine one would want to go to some sort of coil-over setup on this so they could play with spring rates and shock settings, since there'd be more leverage on the spring if the pocket were in the same location on the arm (and moving it would have its own set of down-sides).

Originally posted by airrj:
The tie rod is to long, and so making the track wide would only make that even worse.
So long as I've got my imaginary fabricator building me a set of longer lower control arms, I may as well get him to hook me up with a center-link that's the proper length for my modified suspension. Of course, he'd also have to set me up with tie rod sleeves and tie rods that could adjust to the proper length with the new center link, and I'd probably want a new sway bar that would link up closer to the spindle.

Any guesses as to how big the differences in camber gain would be between using the typical shorter uppers (I don't know the measurements of any) and longer lowers? (Alternately, how much longer would the lowers need to be to get an optimal camber curve, and would it fit within the wheelwells that way?)

I've read through Herb Adams' book, and while I don't understand most of it, it does sound like track width increase is a good thing, so long as everything else changes to match.

-edit after posting-

Thanks for your input too, Tony, I understand completely what you mean - no diagrams needed. That was the thought process that I started with this morning while sitting in stop-and-stop traffic... and with nothing else to do but wait, I started thinking about the front suspension (doesn't everyone? ;) )

I have been thinking of a cheap (homemade) independant suspension for a little wago I want to build for my daughter...

Hard to write down your thoughts without hitting the car in front of you...


And a bigger question (I think)...
Why doesn't one of these companies making dropped spindles make a tall set with proper steering geometry for the A-bodies... I think it could be a big seller...

I see dropped spindles for using smaller 78-? A&G-body brakes, why not using the big 12 inch stuff???

It is all another very interesting idea. Check for a company called Flexi-Flyer. They make a stock appearing lower A-arm that is longer for circle rack cars. Again it is designed to widen the track width. I can't prove or disprove any of your ideas. I think you have a valid point. I guess it will take a test car to try it, or modeling it up in a Chassis Simulator. Why doesn't one of these companies making dropped spindles make a tall set with proper steering geometry for the A-bodies... I am hoping to get to the Circle Track show this fall in Syracue, NY. I plan to talk to some of the chassis fabricators about this very subjuct. It looks like the build many, many types of custom spindles, however I don't have the knowledge to read their catalogs to know what I may need. A face to face conversation hopefully will shed some light.

Tony,

I just made airline reservations today. I will be in your backyard again this fall. :D

RJ,
Thats great... Feel free to stop by if you have the time...

I just had a new concrete pad poured on the side, and hopefully I will be cleaning up that other Chevelle (with the baby, I doubt it, but it my plan)... And if you need any "beta" testing done for your work, I will volunteer my daughter...

I have also asked the spindle question many times. With all these companies making dropped spindles, why not cast tall spindles for Chevelles with the steering arm in the stock spindle location? That would eliminate the slight bump-steer issue with running tall spindles while still providing the better camber curve.

I'm sure there's a market for tall spindles with stock steering arm geometry. If they were available, I'd buy them!

Troy

Check out either Stock Car Products or BSR for a Grand National front spindle. The Winston Cup and GN chassis builders have been using a spindle similar to the Chevelle one for years and it is still made. The only difference from a Chevelle spindle is the lack of a steering arm and lower ball joint mounting boss....
This allows chassis builders to make their own steering arm lengths and spindle heights with a bolt on part.
I had the idea to shave the lower BJ point off my spindles and make a bolt on arm that would mount the lower ball joint the same distance away from the upper as on a "tall" spindle, and have the correct steering arm length as on the factory arm. Just haven't had the time to get after it yet.

As for longer lower arms, cost of manufacture of lowers vs. uppers tells me I'd make the uppers too if I was GW or one of those guys.
Also going disc moves the tire out already. Only would get worse with a longer arm. That is unless you wanted to talk about minimizing scrub radius :D

K