Upper Control Arm R1/R2

[Doug B]

Many years ago, I sent for a replacement part for my Avanti II. They sent the wrong one. Anybody need one? It's time to reduce my inventory. The list enclosed with it has:

1 arm #532181

1 shaft #1546662

2 bushings #1553430

2 retainers #532187

2 screws #1541700 (it says, use 519379)

Everything spotless, with original paint.

How about low-back front seats? No tracks.

Make an offer. Located in Ottawa, Ontario.

[mfg]

It sounds like you have one NOS '51-'52 Studebaker passenger car, and '64 Avanti R3, upper control arm assembly.

It's too bad that you don't have a pair of them!

[Kennie B.]

It sounds like you have one NOS '51-'52 Studebaker passenger car, and '64 Avanti R3, upper control arm assembly.

It's too bad that you don't have a pair of them!

What is the difference between R1 & 2 upper control arms vs the R 3 & 4? Outwardly they look the same but the lesser cars use rubber bushings vs metal. This last weekend Avanti Lady had a pair on E-Bay for $500.00 with shafts and bushings.

[mfg]

The R3-4 upper arms give a firmer ride as they are 'all steel' as opposed to a rubber encased steel bushing on the inner shaft.....But what really nice about them, (IMHO), is that they can be greased with chassis lube, and if they are faithfully maintained (lubed), will last indefinitely!

As most all you folks already know, the 'rare' '64 Avanti R3-R4 front suspension upper control arm is exactly the same arm Studebaker used in all their '51-'52 passenger car models, both 6 cylinder and V8.

[ron@crall.com]

Have them in my 63 and put them in a 60 hawk back when parts were cheap. It also had the rear sway bar out of a 53 land cruiser, same as the one used in the super hawk's

[Kennie B.]

Can you get a little more caster with the metal bushings?

As I look at the bushing and shaft, they are threaded on their bearing surface. Back in the early '80's I rebuilt the front suspension on a Mercury Cyclone and similar shafts were used there. I wanted more caster on that car so I assembled the arms with the shafts as far forward of midpoint as I thought reasonable to get as much caster as possible.

I realize that Fords used ball joints so the kingpin didn't bind but shimming the inner shafts could solve that.

In short Doug, I might be interested. How much and how much does it weigh?

[mfg]

No more caster with the threaded bushing type upper arms. The threaded bushings are screwed into the arm (& onto the inner shaft) till they bottom.....The upper control arm inner shaft on a Stude doesn't 'run' in its bushings like the Stude upper arm OUTER pin does!

[Kennie B.]

How close to the bottom of the bushing bore is the end of the shaft? In the Cyclone there was a total of three or four turns from being bottomed at the one end vs the other. At two turns I still felt there was plenty of bearing surface in contact at each end to be strong and stable.

[mfg]

I'd have to measure one that I have, but I'd guess the end of the shaft is very close to 'bottoming out' in the bushing.

If you're really looking for more caster, (either pos or neg) shim the upper and lower inner shafts at opposite ends.

PS....Read 'Avanti Caster' on 11/1/15's AVANTI TRIVIA.......Ed

[Kennie B.]

I'm confused Ed. I get how as the kingpin is shifted aft at the top and forward at the bottom you would need to shim the inner pivots to take care of removing a bind due to the trunnions no longer lining up with their respective bores. How does the action of shimming affect castor?

I'm not yet ready to rebuild the front end, far too many other fires to put out first but it is on the list. Just as soon as I find a round tuit. Oh, a little spare change would help too. In the meantime I keep sucking up as much knowledge as I can.

[mfg]

I'm confused Ed. I get how as the kingpin is shifted aft at the top and forward at the bottom you would need to shim the inner pivots to take care of removing a bind due to the trunnions no longer lining up with their respective bores. How does the action of shimming affect castor?

I'm not yet ready to rebuild the front end, far too many other fires to put out first but it is on the list. Just as soon as I find a round tuit. Oh, a little spare change would help too. In the meantime I keep sucking up as much knowledge as I can.

Well, by shimming the inner arms as described, you're increasing the angle of the kingpin either forward (more negative caster) or rearward (more positive caster)....over and above the factory adjustment provision in the upper control arm outer pin.

[Kennie B.]

But how does shimming move the outer end of the "A" arm fore or aft?

For caster to change, the top of the kingpin needs to move fore or aft in relationship to the bottom.

At each end of the kingpin, there is a trunnion. The trunnions run parallel to one another. The threaded pin fits in its bore rather loosely to allow for some mis-alignment of the "A" arms making adjustment possible. It is rather limited in how much shift can be gained before the pins will bind in the kingpin ends. Now that would be where shimming would come into play. It would allow for a greater shift of the "A" arms location by re-aligning the bores in the end of the arms so there would not be binding in the trunnions. The play that exists is typically enough to allow adjustment with the designed limits but if you were to shift rearward the upper arm an 1/8" that I imagine one rotation of the shaft within the metal bushing, I bet that there would then be some binding when the trunnions are adjusted to the greatest positive caster adjustment.

Then again, I could very well be missing something. That's why I am discussing this here.

[mfg]

That's OK...It IS confusing, and I sure don't want to add to that confusion....but try picturing the LEFT front suspension viewed from the side.....by shimming the inner shafts, upper and lower, at opposite ends, one would be 'tilting' the entire assembly either + or -......this would, of course, be added to the rather limited range of factory provided adjustment at the upper outer pin....Ed