Upper control arms & balljoint angles for tall spindles

[jarretts70]

I'm looking at all the tall spindle / tubular control arm combinations for my 1970 GTO. Lots of options, and I'm starting to get a little cross-eyed from staring at my computer screen....Some (most?) of the control arm kits are advertised as being compatible with both stock height & tall spindles. That's the part that is confusing me, as it seems to me the tall spindles should require a different UCA.



I want to make sure I've got the theory behind ball joint angles correct correct, although it seems basic to me. When at ride height, the ball joints on a stock A-body would be more or less in the middle of their range of motion. Raising the upper control arm via a taller spindle (or a taller ball joint) will put the upper ball joint more to one side of it's range of motion, hence the concern of putting that ball joint in a bind when the suspension is under compression. The solution is to re-clock the ball joint mount pad of the UCA to accommodate the taller spindle. If you were to look at the UCA's from the front of the car the driver side UCA would have its ball joint pad rotated slightly clockwise; the passenger side it would be rotated slightly counter clock wise. Is this correct? And if so how can the same UCA be used with both stock height & tall spindles?

[79T/Aman]

you are correct, especially if the car is lowered and has tall spindles.

[Peter Mc Mahon]

Is the hole of the female socket of the ball joint not round?

[stab6902]

You are correct in your understanding. Ideally the control arms would be specific to your ride height and spindle height, but apparently the ball joints have enough extra travel (relative to an all stock setup) that it's not a problem. I'm running 0.9" taller ball joints on a 72 Skylark with stock arms and 2.5" lowering springs and I've never had any issues.

[Volks]

Hey Ryan do you know if you were able to get any positive caster with your set up?

Don

[stab6902]

Hi Volks, to be honest I haven't measured where my Buick is at alignment wise since I did the suspension work. I was told it was aligned before I bought it (but no print out) and then I set the toe after all the work and started driving it.

On my 68 Firebird (very similar setup - lowered 2.5" with springs, 0.9" taller ball joints, stock arms), I was able to get 5 degrees caster with -0.5 degrees camber. The more negative camber you are willing to accept, the more caster you will be able to get. From what I've read, it's common to be able to get 4-5 degrees of caster with stock arms on the A-body's.

I wouldn't recommend going too crazy with positive caster using only aftermarket upper control arms (6-8+ degrees) just for aesthetic reasons. The wheel moves rearward in the wheel well when you do this and starts looking funny in my opinion. You can do the trig to figure out how much your wheel will move back for a given spindle geometry and alignment target. Some people don't care, but I'm pretty picky about getting the stance just right.

[jarretts70]

Hey guys, thanks for the input. Good to know I've got the theory correct....

I spent a couple months last year researching different spindle/control arm options. Got sidetracked on a different project before I bought anything & now back into decision making...I understand that manufacturers aren't going to give away their secrets, but I find the lack of specifications from the manufacturers frustrating. I'm tired of reading ads for products that make claims like "geometry corrected". I want to know HOW the geometry has been corrected. Has the ball joint been moved rearward, & by how much? How many extra degrees of positive caster? What is the KPI angle? I've read a couple ads claiming that "Brand X" control arms improve the camber curve. I'm no engineer, but as I understand it the only way to change the camber curve is to change the height of the suspension pivot points & just changing control arms doesn't do that. What gives?

Sorry for the rant....

FWIW, car is a '70 GTO. I got it as a stripped carcass years ago & have been piecing it back together since. It was a factory disc brake car - someone stripped all the brakes. spindles etc. long before I got it. I figured since I need spindles & control arm anyway I might as well do a tall spindle/UCA combo. Building it as more of a GT car than full out track car; in fact the car will never see a racetrack unless its from the parking lot....

[Volks]

Ryan I don't think I ever got 5 degrees out of stock arms. Maybe 2 to 3 with the old offset upper control arm shafts. Although most were regular street/strip set ups with close to 0 degrees camber. Agree can get more caster if you're willing to go negative camber.


Jarrets I hear you. Lots of choices out there. And yes "geometry corrected"? Is the upper ball joint moved? Is the lower moved? I actually have an old set of Global West arms with the del a lums that have been on my shelf forever. They have stock position ball joints and I think I'm just going to use them instead of the newest, greatest, latest ones out there. Probably with taller upper ball joints, maybe lowers too, stock spindle. My car is a 71 Chevelle Convertible that will be a street cruiser, only, nothing more. I'd really like to know if you fixed the camber curve with the taller spindle would you really feel a big difference going from 3 degrees caster to 5 on a street car. Or 2 to 6? You don't really see anyone saying that if you have an A body you need to add X amount of caster to really feel a difference. I know on our drag cars we just add as much caster as we can get with what we our working with. It does help on the top end.

[stab6902]

For what it's worth, I share everyone's frustration with the lack of real information about the suspension parts that are marketed to us. Sometimes I wonder if they know what they're selling themselves. At the very least there's a disconnect between engineering and marketing, which doesn't help inspire me to spend $1300+ on a set control arms that may or may not improve performance.

[jarretts70]

Good to know others share my frustration. Misery loves company...

It extends to the spindles as well as the control arms. Pretty much all the "big" players in the suspension game for these cars offer a tall spindle. First, to me they all look suspiciously similar. The ridetech/Fatman/Chassisworks steel spindles all look the same to me in pictures (same forging?). Heidts / Speedway G-comp look the same as each other...

All of these spindles are marketed as fitting 1st gen F-body as well as A-body which makes sense. Some of these spindles are marketed as having relocated steering arm mounting locations to help with bump steer. However - 1st gen F-body use a totally different steering arm than an A-body - the bump steer issues are different. On a Camaro the steering arm needs to move "down" - on an A-body it needs to move up. I'd be lying if I said I totally understand all the math but I read a couple threads written by Marcus at SC&C explaining it, and I think the guy knows his stuff. Bottom line is that the same spindle cannot be "bump steer corrected" for both an A-body & an F-body? Still confused...

At the moment I'm leaning towards the Chassisworks billet aluminium spindle / steering arm setup. It's pricey but I like the fact it uses a dedicated A-body steering arm. And I can use my existing disc brakes. Just need to figure out which UCA to pair it with...Either that or the Detroit Speed setup. I think(?) their spindle is a dedicated piece with steering arm mounting holes ion the correct place for an A-body.

[pitts64]

I bought the set up that has the most favorable reviews, the SC&C Stage 3..

[Rod]

The ridetech/Fatman/Chassisworks steel spindles all look the same to me in pictures (same forging?).

yes the same

Heidts / Speedway G-comp look the same as each other...

no there different the heidts is shorter, the visual copy is close

hope that helps

[jarretts70]

Hi Rod, thanks for the info! Helps a lot.

[David Pozzi]

In the Proforged upper ball joints, the .9" tall stud has a thicker shank where it would hit the housing at full angle, so this ball joint has less angle capability than stock. The shank diameter was increased to maintain strength. The .5" tall Proforged has a standard dia shank and has more clearance. The .9" length was chosen to keep stress in a safe area, taller wasn't safe & they would have had to make the shank even thicker.

I tested the Proforged .9" tall on a Camaro and they clear OK at full bump but you wouldn't want to do a Guldstrand mod with it, there would be binding. You could do a .5" tall UBJ and G mod and it would clear fine due to the smaller shank.

In a perfect world, the A arm ball joint flange should sit 90 degrees to the ball joint stud at normal ride height. As long as it doesn't bind, you can get by ok which is what most of us are doing.

[jarretts70]

David, thanks for your input, that's good info.

I pulled a stock UCA out of my pile of parts & set it up on the counter so I could measure the distances between the OEM pivot points. Then I did a couple basic CAD sketches. As I calculate it going to a .5" taller ball joint increases the operating angle of the bj by only 3 degrees - bear in mind these were quick measuresments & sketches. I could be out by a degree...

I could combine .5" taller upper bj's with .5" taller lowers as well, all in the original control arms (offset shafts). I'd get 1/2" lower stance and an effective spindle height 1" higher than OEM & still be able to get a proper alignment. Plus very little worry about ever putting the ball joints in a bind.

The question is how much camber curve improvement will I see with 1" more spindle height? To me it makes sense that any improvement is better than none, but I'd be curious to see if anyone has actually crunched the numbers.

[67King]

I understand that manufacturers aren't going to give away their secrets, but I find the lack of specifications from the manufacturers frustrating. I'm tired of reading ads for products that make claims like "geometry corrected". I want to know HOW the geometry has been corrected.

Get some graph paper and draw it out. Imagine you are looking at the vehicle head on. The biggest thing at play here is the camber curve. If you look at the stock suspension, you'll notice that the upper arms are much shorter than the lower arms. That means that for every unit of height change (call that the Y direction), you will have more travel in the other direction (X) that is parallel to the track width measurement. So when you travel, the upper control arm moves more than the lower control arm as it relates to camber.

Got it? Good. Okay, now if you look at the stock setup, you will notice that the upper control arm's pivot point (where it rotates, and is bolted to the frame) sits ABOVE the center of the ball joint. That menas that as the suspension is compressed, the upper control arm will push the top of the spindle OUTWARD. That is BAD. It creates POSITIVE camber, which reduces contact patch. The way every one of these kits fixes that is to move the location of the upper ball joint relative to the lower control arm. In other words, the distance from the center of the two ball joints increases. That moves the upper control arm to a point where it is (approximately) parallel to the ground. NOW when the suspension is compressed, the upper control arm actually pulls in the top of the spindle. That creates negative camber, which is GOOD.

Two basic ways to do that. One is by using tall ball joints. Cheap and easy, but doesn't fix other issues. The other way is to use a taller spindle. That's what the old B-Body conversion from 20+ years ago was all about. Only now, the manufacturers are started addressing bump steer and caster.

As far as caster goes, that is the angle of the wheel, or how "laid back" it is, for lack of a better way to put it. Now, imagine yourself looking at the suspension from the side. If the line from the upper ball joint to the lower ball joint is perpendicular, that is zero caster. If the top ball joint is ahead of the lower one, that is negative caster (kind of how the casters on a shopping cart are, where the axle is behind the pivot). If the top ball joint is behind the lower one, that is positive caster, kind of how the front forks of motorcycles and bikes are. So how do you get that? You can shim the rear of the upper control arm which will cause negative camber (stationary) and also add positive caster. Or, you can change the geometry of the arms. My understanding is that all of the designs out there increase caster by changing the upper control arm so that the ball joint is moved rearward.

Hope that helps.

[jarretts70]

67king - I alredy have a pretty good grasp on the basics as you outlined them. I'm looking for actual numbers. How many degrees of camber improvement would a person get as effective spindle height increases? How many degrees of ball joint range of motion are lost? Etc...

I attempted to dust off my AutoCAD skills this morning & drew this out. I have a bare frame & OEM control arms that i measured to know control arm length & pivot points. I don't have a stock spindle, so I turned to the internet. What I found was an effective height of 7" for an OEM setup - this seems short to me. I would think 7" spindle height plus ball joints would net an effective height of around 8.5" but that just a wild ass guess....

I drew it up with a couple assumptions just to make it easier to draw. One, I assumed zero camber at ride height. Two, I set lower control arm pivot points level with lower ball joint pivots (in real life I believe the bj's would be downhill of the inner pivot points). When I draw it with an effective spindle height of 7" there is a positive camber change of 4.58 degrees @ 2" of compression.

When effective spindle height increases to 8.5" I still see positive camber change, but much less of it - around 1.5 degrees.

Also, when adding the 1.5" to the spindle height the UCA has to move in by almost exactly 1/2" to maintain 0 degrees camber @ ride height. Makes sense to me as I believe the typical tubular UCA is 1/2" narrower than OEM.

If anyone has an oem spindle they can measure I'll correct my drawing & see what happens...

[jarretts70]

Barely finished typing & had an idea. I don't have a stock spindle to measure, but I do have a 1978 Trans Am in my garage....measured it instead.

The effective spindle height on the T/A is about 11". I figure it stands to reason an older A-body with a tall spindle swap should be the same. When I draw it up with 11" effective height I get 1.536 degrees negative camber (still @ 2" compression). UCA has to move inward by 11/16" to maintain zero camber @ ride height.

So it would seem I'm on the right track...

[jarretts70]

All this measuring & drawing got me thinking about suspension geometry diagrams...New question.

When you look at a diagram of a front suspension geometry they are typically drawn from the front, facing the car. They will show the pivot points where the control arms attach to the chassis, as well as the pivot points of the ball joints. Then lines are drawn thru those points to calculate instant center, roll center, etc....

But on the car the mounting points of the control arms are not in line with each other (IE, parallel to the center line of the car). For example, the rear lower control arm pivot is inboard of the front pivot. When trying to diagram this should I take the average distance from center line of the two pivot points?

I'm kind of getting off track from where this thread started, hopefully this turns out to be useful information...

[79T/Aman]

from a top view draw a line through the lower ball joints, where that line intersects the lower A-arm bushing line will be your effective lower arm length.