Custom Tubular Lower Control Arm?

[SSTuner]

I did verify the thickness of the photo in post #11 above and its 1/2".

I'm concerned on Matt's comment above and hopefully he can address the concerns of "suitabilty".

[exwestracer]

IMO that design isn't suitable for the weight of your vehicle.

My thoughts exactly, Matt. I think if he braces the plates out to the hole centerline it should be ok. Somebody needs to have a talk with whoever designed those...

[carguykeith]

Attachment 54655

I will recheck the measurement.

Just to clarify, you want me to measure the thickness as shown it the "red" circle?

Ok I think you are measuring what I would call width here, I'm not as concerned with the distance between the concentric circles but that actual plate thickness. Though in this picture it does look thicker than the others... I'm still guessing 3/16" but even if it's 1/4" I would want some gusseting, flat plate just doesn't resist bending very well.

Oh and you can get a reamer for your spindle pretty cheap from circle track suppliers, that's what I would do.

[exwestracer]

I could believe it's 1/2" plate... If you look closely at the photo in poat #11, there's a pretty wide shadow across the edge. No substitute for proper design, but at least it's not thin AND unsupported...

[MrQuick]

That would be acceptable for an upper arm but very sketchy for a lower....imho

how is the tire clearance?

[Apogee]

Given your existing hole size and unknown tolerances, it seems like the 5/8" ball joint could be your best bet, even though it will require machining of both the lower control arm and spindle to make it happen. The only difference between the 9/16" and 5/8" spindles for the 1991-1996 B-body applications was the depth that they reamed the lower ball joint hole.

Not to get too far off topic, but aside from the whole design issue, I'm not digging the smoothed welds on the arms either. The only way to make it worse would be to chrome it...please say you're not going to chrome it.

Tobin

[SSTuner]

Here are some additional photos and actual caliper measurements on both the upper and lower control arms:

Lower Arms:




Upper Arms:



I hope this will clear up some of the measurments.

[exwestracer]

I hate to say this, and I know it wasn't your original issue here; but those things are pretty haggard...seriously.

If designed correctly, there is no reason to use thicker than 1/8" plate on the upper arm, and 3/16 on the lower. They will probably work OK if you can get the balljoint issue sorted out; but they are WAY heavier than need be, for no real gain in strength...

[Navy Lifer]

I've modified quite a number of OE (stamped) B-body lower control arms to accept the larger (Moog K6141 & equivalent) ball joint over the past 10 years. OE B-body LCA's were offered with the larger ball joint, as was already mentioned, but were discontinued by GM SPO a number of years ago, so one option became cutting out the stamped area for the standard ball joint and welding in a machined ring in it's place. The ID of the ring I'm using is 2.180", which gives an interference fit of 0.010" with the ball joint, and has worked quite well for all of the arms I've put together--at least 100 of them. The ring OD is 2.650--wall thickness in the press area is 0.235", nice and beefy. I'll post some pictures if anyone is interested in seeing them.

The knuckle issue has been served by GM for quite a long time, as the 5/8" parts (for the larger lower ball joint) have been available since production (mid-95 & 96 9C1)--the question at this point is how much longer they will be available. The PN's are 18021377 & 18021378--these use Set3 & Set6 bearings, and will back-fit all "tall knuckle" (spindle) applications from the 1970 Camaro, all the way to the 1996 B & D body--as long as the ball joint(and LCA) is changed, too. The topper is that these knuckles are quite inexpensive--probably less than buying the reamer and, if necessary, paying a machinist for their services to fix what you might screw-up yourself...otherwise you end up with unique door stops.

listing from GM Parts Direct (reference only - no endorsement)
GM PART # 18021377 & # 18021378
CATEGORY: Steering Knuckle
List Price: $100.44
Price: $58.97 (ea) - before markup for shipping/handling, about $150/pair delivered

I'm not sure what the attraction of fabricated tubular control arms is--especially lowers. I look at these parts (Ray's) and conclude that I'm better off with the OE arms. A B-body weighs over 4000#, and I am not a fan of coil-over suspension conversion on these cars--there is a big difference in the load concentration using coil-overs which mount to a "universal" LCA, not to mention what it means to the shock absorber function, the bushings at each end of the shock, etc. As also mentioned, I doubt that the weight of the fabbed arms is any less than the OE parts--and I'm not aware of any testing that has been conducted by any fabricator to show what is really superior about their parts vs OE.

Upper control arms are a different matter, since that is where the caster & camber are controlled.

Finally, Ray contacted me on another Forum, and I realize now that I gave him bad information--the LCA's he has will need to be re-sized to accept the K6141 ball joint--as several others have also mentioned. I did offer that he could weld in a couple of my machined rings to provide correct fit, but it would still require some cutting/grinding, fitting and welding to work.

[Apogee]

Bill, I was wondering when you'd make your way over here from the Impala SS forum. Welcome to pro-touring.com. Nice first post...way to bring the tech.

Tobin
KORE3

[keithq69]

This is a good thread.
Navy Lifer made some good points and knows way more about this application than I ever will.
One thing caught my attention though. You said that the caster and camber are controlled by the upper A-arm.
The way I see it, the caster and camber are controlled by the relationship between the upper and lower. You could add caster and negative camber by moving the lower ball joint out and forward just the same as moving the upper ball joint in and back.
I've seen a few 69 Camaro's in the past where the upper control arm is moved back to add caster and the wheel doesn't look like it's centered in the wheel opening anymore.
Moving the lower ball joint forward could solve that problem.
Am I wrong in thinking that?

Sorry, a little off topic.

Keith.

[SSTuner]

Bill, again thanks for the info you provided on your post above. Welcome to this forum.

BTW: I have my parts guy searching for the above knuckles part numbers.

[shep]

This is a good thread.
Navy Lifer made some good points and knows way more about this application than I ever will.
One thing caught my attention though. You said that the caster and camber are controlled by the upper A-arm.
The way I see it, the caster and camber are controlled by the relationship between the upper and lower. You could add caster and negative camber by moving the lower ball joint out and forward just the same as moving the upper ball joint in and back.
I've seen a few 69 Camaro's in the past where the upper control arm is moved back to add caster and the wheel doesn't look like it's centered in the wheel opening anymore.
Moving the lower ball joint forward could solve that problem.
Am I wrong in thinking that?

Sorry, a little off topic.

Keith.

The lower control arms from SC&C are designed in this manor to help to center the wheel in the opening.

[Navy Lifer]

Keith, Brad, Tobin, Ray and all--thanks for the welcome! I'm just glad to have the opportunity to contribute my "little bit" in areas I feel like I have something worthwhile to say....

One thing caught my attention though. You said that the caster and camber are controlled by the upper A-arm. The way I see it, the caster and camber are controlled by the relationship between the upper and lower. You could add caster and negative camber by moving the lower ball joint out and forward just the same as moving the upper ball joint in and back. I've seen a few 69 Camaro's in the past where the upper control arm is moved back to add caster and the wheel doesn't look like it's centered in the wheel opening anymore. Moving the lower ball joint forward could solve that problem. Am I wrong in thinking that?

Keith,
Technically you are correct. The position of the lower ball joint is fixed, typically, as that is one of the points that establishes the wheelbase of the vehicle (the other being the rear axle)--to avoid the appearance issue you mention with the 69 Camaro--properly hung sheetmetal is one thing, but the 69 Camaro did have a different wheel opening style than 67/68 Camaro, so I think that is part of the issue, too--a visual "thing" that can be a challenge to nail down. Granted, the knuckle/spindle position is movable by way of the UCA shim pack or through use of an adjustable UCA (SPC for example), which will incline the axis of the knuckle (where the 2 ball joints are in relation to each other) but there is a limited range of movement that will keep the front wheel in proper relationship with the LCA pivot point as well as steering arm connections, etc, unless considerable effort is made to re-engineer the geometry. That same adjustment for greater caster can quickly take a car visually from perfect to weird, especially with the popularity of larger diameter rolling stock and very tight clearances between body and tire/wheel.

Some aftermarket replacement frames for F/X body, for example, start with a "clean sheet of paper" instead of trying to make the OE design work, when much better stuff is available today--thus the popularity of C4/C5 front end integration into older chassis, such as what Newman Car Creations, Detroit Speed, Art Morrison, and others offer (no intent to leave anyone out or include some I shouldn't). While not the specific subject of this discussion, the suspension of the 67 Camaro never had large wheels/tires to keep planted on the pavement when it was built, but tire development over the past 40+ years has changed all that.

In Ray's case, the 94-96 Impala (and all 77-96 B-body production) has suspension geometry that is a very close cousin to the 2nd-gen F-body, born in 1970, so it is by no means a unique design--it actually evolved from the 73-77 A-body Chevelle/Monte Carlo (116" WB) and all of these vehicles used the same basic front knuckle--overall knuckle height, steering arm location and spindle position, with identical or very similar UCA/LCA--and all were "front steer" with the steering gear forward of axle/spindle centerline.

As far as actually moving the LBJ forward, I don't know that you will typically see that as a solution. The LCA takes the brunt of vehicle loading in cornering situations and needs to be STRONG. An adjustable front LCA is either going to be inherently weaker, or it will end up much heavier than it really needs to be in order to compensate for being adjustable--the stamped OE arms are a marvel, really, since they start out as a flat sheet of steel, and once they've been pressed/formed, the strength to weight factor is remarkable.

The lower control arms from SC&C are designed in this manor to help to center the wheel in the opening.

Brad, I think you may be referring to REAR LCA's, like the Currie pieces offered by SC&C. There are probably other situations that call for them, but the 93-96 Chevy B-body sedan was a factory hack-job, in reality--when the body wheel opening was changed in 1993 to the more open style, the rear door contour was not changed, and the modified opening created a visual skewing of the rear wheel into the forward end of the quarter panel, when in fact it had not moved at all.

GM already knew the car was going away in a couple more years, so there was no engineering funding or interest in fixing a visual mis-cue. Aftermarket to the rescue, with numerous versions of "extended" rear LCA's to move the rear axle back between 1/2" & 3/4", some being fixed, and some adjustable, but always necessitating addition of adjustable rear UPPER control arms--and many nightmares dealing with changes to rear suspension geometry, pinion/driveline angles, trans tailshaft spline/slip yoke engagement (ie. reduced torque capacity/higher load on splines), discussion & disagreement over the need for a longer driveshaft to compensate, etc. have resulted since.

WARNING - I often write long responses!!!

[keithq69]

Hey Navy Lifer, no worries about the long responses, I do the same sometimes.

As far as what you stated above, I agree, when you have a stock suspension that you are trying to get more caster from the upper arm is where the adjustment is.
What I meant was that if you are starting from scratch and making your own set of control arms like these you could move the lower ball joint placement forward to allow for more caster.

A friend of mine has the Speed Tech uppers on his 69 Camaro, I think the car has between 5 and 7 degrees of caster, if you look closely it looks like the wheel is sitting just a bit rear of center.
I have seen a few others that looked the same.
Back in 1999 I built a 69 Camaro and used C4 front suspension on it. I built my own front subframe. I built a jig that I centered in the wheel opening where I wanted the wheel to sit and had a flange that was the same distance apart as the inside of my wheels.
I bolted the spindles to the flange, set the caster and then built the suspension mounting points around that so when I was finished the wheel sat where it looked best.
It made it easier to turn the 275's in the front without hitting the tire on the back of the wheel well.

Keith.

[exwestracer]

A friend of mine has the Speed Tech uppers on his 69 Camaro, I think the car has between 5 and 7 degrees of caster, if you look closely it looks like the wheel is sitting just a bit rear of center.
I have seen a few others that looked the same.
Keith.

It also depends on how much drop is incorporated in the spindle. With 0 drop, the LCA will have more effect on caster. The higher the amount of drop, the more the upper ball joint location affects caster.