Getting more caster by adjusting the upper control arm

[KongaMan]

The front end on the 64 is going back together, and -- like many -- I intend to change the alignment specs to get more positive caster with radials.  My understanding is that the stock setup might only get one a couple of degrees before you run out of adjustment room. Stock spec is to center the upper shaft in the control arm and fine tune it with shims.  So, I'm thinking that If the shaft isn't quite centered, it will change the initial caster.  Which means that a couple of extra spins of the shaft might move the arm back enough to get more positive caster.

 

Any reason this won't work?

[jsgun]

I'm new to buick, so I'm not positive. But the top shafts look much like the mustang design, and that being the case, they won't be adjustable. The nuts at the ends only provide tension on the bushings, and don't really allow for much adjustment. I imagine you can adjust the shim stacks front to back to get more caster.

[jsgun]

Maybe you could have some new upper shafts made that pull in and lower the arms. You could get pretty crazy with roll camber too. I've often wondered if Chevelle parts would fit. If so, that opens up a lot of options.

[Seafoam65]

                 I have radial tires on my 65 with the stock specs on the front end alignment, and it is the nicest driving car

I own at highway speeds out of 8 cars in the stable, including a 2013 Mustang and 2010 Camaro. I don't know why you would need to

mess with the caster  on the car. Just putting radials on it makes it drive like a dream.

[KongaMan]

2 hours ago, jsgun said:

I'm new to buick, so I'm not positive. But the top shafts look much like the mustang design, and that being the case, they won't be adjustable. The nuts at the ends only provide tension on the bushings, and don't really allow for much adjustment. I imagine you can adjust the shim stacks front to back to get more caster.

They're very much adjustable (before they're installed, of course). The shaft is positioned by spinning; as it pulls into one end, it pulls away from the other.  Stock spec is to center it, but there's no reason that I can think of that it has to be that way.

 

BTW, it's not clear that the caps provide tension. Rather, it appears that they're just (for lack of a better word) nuts to hold the threaded shaft. It's the same design as the idler arm.

 

[NTX5467]

Many aftermarket bushings are oriented toward compensating for crossmember sag (which seems to be more prevalent than I ever suspected, all the way back to the '55 Chevies!), so that stock specs can be obtained.

 

With stock production bushings, you can probably get about 2 degrees of positive caster, which is at least another degree than production specs.  But straight-line "driving" or "self-centering after a turn" is not a real reason to increase the caster.  When you increase the caster toward the maximum stock spec, you also increase the negative camber of the outer wheel in a turn, which can keep the sidewall of the outer wheel in the turn better braced against the corner (i.e., more upright as the chassis leans, effectively adding positive camber) for better cornering performance.  With a wider wheel rim, some tread-edge wear might be evident.  "Wider" as 7" or wider, from my own experiences with 7" wheel rim widths.  And this "trick" works with bias ply, radials, or anything in-between.

 

IF all of the front suspension bushings will be new, install them as specified.  Set the suspension alignment to specs, minimizing toe-in for radial tires (min spec), maximizing caster (upper end of the spec range), and keeping camber to stock specs.  It might not be possible to hit ALL of the specs, but getting them in that general orientation will work pretty well.  And, if you want to be even "closer", you be sitting in the car when the alignment is done, with about 1/2 tank of fuel.  Then, recheck the alignment about 5000 miles later after everything has a chance to "settle-in".

 

NTX5467

Edited June 16, 2017 by NTX5467 (see edit history)

[KongaMan]

It's still not clear why this wouldn't work, so we applied a little math to the problem to see how much adjustment we could get by moving the shaft off-center in the control arm.

 

The distance between the upper and lower ball joints is ~11".  IIRC, the shaft has 3/4-10 thread.  This means that every rotation of the shaft moves the arm .1" forward or backwards.  Basic trigonometry tells us that every such movement changes the angle between the two ball joints by .52º (sin^-1(.1/11)).  So, for every two rotations of the shaft, you should be able to get another ~1º of positive caster.

 

So...  Spec is to center the shaft in the arm. However, a lot of folks report that they can get only 2-3º of positive caster from the stock configuration using shims.  If you start with the shaft off-center by 4 turns, you should get another 2º of positive caster from the same setup without touching anything else. That, in turn, might easily get you to +4º.

 

Where would this go wrong?

[KongaMan]

Well. here's where it might go wrong...   After centering the shaft in the arm, you only get two turns of the shaft before it's at the end of its travel.  Which means that this will get you only one extra degree of caster.  Still, one is better than none, no?

[jsgun]

It'll cost some money, but I'd look at having some offset shafts made from billet steel. I believe the dirt track guys have them made, you might be able to find a supplier that will cut them for you.

[telriv]

Do a search & you'll find out what I did back in the 80's.

[KongaMan]

22 hours ago, jsgun said:

It'll cost some money, but I'd look at having some offset shafts made from billet steel. I believe the dirt track guys have them made, you might be able to find a supplier that will cut them for you.

 

I suppose one could do that, but that seems like overkill.   That is, it's a lot of money to spend for minimal benefit.  If you wanted greater adjustability on the cheap, you could machine a little off the front end of the shaft (or add a little thread) so that it screwed in further. That would move the arm back even further.

 

The old trick was to shave down the reaction rod bushings (or use thinner bushings from a different application) to pull the lower arm forward, but that always seemed a bit inelegant.  The way I figure it, the upper arm is made to be adjustable.  Why not use what's already there?

 

As it is, you can probably get to +3-4º using the system as designed.  That should be enough.

[jsgun]

On my old mustang, I had the Arning "Shelby" drop done, where the mounting holes for the upper arms are lowered an inch. Some guys do 2 inches. I also replaced the upper and lower arms, and strut rod bushing with spherical bearings. Made it into a completely different car. It actually handles like a modern car now. It's also harsh enough to knock the fillings out of your teeth at low speed, but anyhow, I don't really believe in overkill. But I get your point. I spent $2k to make a 50yr old car handle as good as my GF's toyota.

 

FWIW, I had a 79 Chevy Malibu years ago, and I rebuilt the suspension. I put poly bushings everywhere. The upper arms have an offset balljoint, it's closer to one bushing than the other. I installed it wrong.... I assumed the ball join would be offset to the rear, to give it camber. I took it to a shop to get it aligned, and it had 13 degrees camber. I had to drive it like that for a week, until I could get it apart on the weekend. t drove ok, other than during sharp turns, the outside corner of the car would rise. Backing up, it would literally drag the tire sideways. It was a learning experience.

[jsgun]

Schwartz Performance built a 82 Fleetwood for racing, and one of his tricks was to cut the upper control arm mount off the frame, and relocate it to get better geometry. He's won many races with that giant boat. It's comical to see it racing cars half it's size. Anyhow, it's amazing what can be done with corrective surgery.

[cquisuila]

hello

 

i have a question on suspension lower ball join ON riviera 1966;)

The upper ball join is welded.

 

It is the same thing for lower ball join please ?

Because it is very hard to remove.

 

thank you for your answer !

philip

 

 

[EmTee]

The shop manual shows a special tool used to remove and install the lower ball joint.  I believe this tool simply presses the joint into (or out of) the lower control arm.  If it were my car, I would probably remove the lower control arm so that it could be taken to a shop with a suitable press.

[1965rivgs]

9 hours ago, cquisuila said:

hello

 

i have a question on suspension lower ball join ON riviera 1966;)

The upper ball join is welded.

 

It is the same thing for lower ball join please ?

Because it is very hard to remove.

 

thank you for your answer !

philip

 

 

  No, the lower is not spot welded, it is simply a press fit. There is a tool which is designed to press the lower ball joint while the control arm is still installed on the car called a "ball joint press"...looks like a large heavy duty C clamp with various sized cups to accommodate different applications. I have used the C clamp accompanied by impact guns in many, many pressing applications including brake anchor pins on heavy duty truck applications and leaf spring bushings...a very, very handy tool to have for anyone who works on varied things mechanical.

Tom

[cquisuila]

ok thank you it will be easier that upper...