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Modifying front LCAs... I need internal threaded stock


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Well... I realize that ON-CAR-Adjustable is desired... but I am going the budget route...

 

 

I have some 1" OD 0.065 wall DOM... I was going to use 240HOKE's idea...

 

cut the stock arm 6" from the BJ hole... use the 1" tube and a threaded pipe end to extend the cut LCA... simply screw a 5/8" rod end and jam nut into that pipe extension...

 

I keep looking at that idea and thinking... there is not a lot of safety margin in that design..

1. the tube seems to be the weakest point...

2. the rod end threads are next weakest...

 

 

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The next design seems a little safer... and a little cheaper....

 

frontarmdone.jpg

 

 

It just uses a cut off 5/8" grade 8 bolt and a femake rod end... you cut off the head of the bolt and insert it into the arm... collapse the top of the LCA down to capture the bolt and plug weld the shank and weld the outer perimeter...

 

I would probably use a 3/4" bolt and use an oversize 3/4" shank rod end with a 5/8" eye... the rod ends in that configuration are rated at something like 36,000lbs tensil...

 

 

 

 

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The next design has no explanation...

 

FCArodends.jpg

 

I assume he used internally threaded square stock with a 5/8" rod end... It looks the simplest... It just has to be strong... This is the design I would like to use... but I cannot find the internal threaded sq stock...

 

 

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240Hoke had a great design for the TC rods... It seems simple enough... easy to find parts... the swedged rod is not cheap though... I do not like the idea that it moves the pivot point forward and outward quite a bit...

 

 

 

The one I am really interested in is hard to figure out.... take a look and tell me what you guys think about this design...

 

 

5428t-c_arm1.jpg

 

 

 

 

 

.....

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My thoughts:

3/4" is larger than necessary for the front LCA.

 

I haven't found threaded square stock. I think people are taking a piece of 1/2 or 3/4" plate steel, drilling a hole and tapping it. Easy enough to do.

 

The guy who did my round tubing found a size that was tight enough that it had to be hammered into the cut end of the control arm. He then turned down a threaded tube end and welded that into the end of the arm for a 5/8" rod end. If you do it that way you don't have to cut the control arm open, but you do have to turn the tube end to fit in the smaller diameter tube.

 

Make your control arms at least as long as stock. I mean with the rod end threaded ALL the way in, it should be as long as stock. This will give you more room to add negative camber with the arms.

 

The TC rods with the inner tie rod are a fine idea. What I don't get is how they threaded the tie rod into the end of the TC rod. It kinda looks like maybe they cut the TC rod after the J end, then welded on a tube with internal threads and that's what the tie rod screws into. Looks very similar to what BRE used on their 510's back in the early 70s.

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So that last TC design brings us back to internally threaded stock... I wonder of that design is actually using off the shelf parts... the internal threads couls be from a straight outer tie rod... anyone recognize it????

 

 

 

I am interested in kicking around the idea of using the stock car spherical bearings in cups for replacing bushings for the inner mount for the TC rods...

 

Has anyone found a good parts list for that design?... That would seem to get the best positioning for the inner pivot point...

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  • 2 months later...

I was actually going to buy these, but I reconsidered:

zcar-lca.JPG

The guy says he based his design on the old AZ car arms, but made them on car adjustable. They do look nice. And the 2nd adjustment is out past the mount for the sway-bar end. I also like the elegance of using that tie-rod ball-joint instead of the typical, more complicated mount for the stock ball joint. The trouble is that these are not really on-car adjustable. To adjust you must either disconnect the TC rod clevis and the sway-bar mount, or else disconnect either the inner heim or the outer ball joint.

 

Also, this brings me to another issue that I don't think has been discussed. One extra advantage of the "on-car" adjustable designs (which use some sort of independent turn-buckle mechanism) is that they offer a much finer adjustment. Maybe this is not that important? With single adjustable (and the arms pictured here could be called "triple single adjustable"), you must spin the threaded part (heim, ball joint, whatever) 180* - so your minimum adjustment is 1/2 the thread pitch. Actually, with the design pictured above, if you disconnect TC and SB and spin the center section, you have to go one full turn and the adjustment is actually thread pitch times 2. Not so good. The only buy-able LCAs I've found that have true on-car adjustment (from azcarbum) lack jam nuts (which is odd) and are actually more expensive than the arizona Z car LCAs.

 

The more I think about this, the more I am leaning towards just buying Dave's fancy (non-on-car adjustable :( ) aluminum arms:

frontarm2.jpg

If I build my own, it's gonna cost around $300 for all the parts. And since I'm daily-driving this car right now (yes, I am now deaf and have kidney damage ;) ), I would probably be better off buying a set of stock LCAs to cut up (so that the work on the car is just a quick R&R so I can get to work on Monday). So it's almost like <$200 extra to just buy a set....

 

Or maybe I'm just trying to justify laziness and a lack of creativity.

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Hmmm. A couple of things about that top design...

 

The steering joint is an unknown... How much abuse can that really take??? It might be plenty strong... I dunno...

 

The sway bar will attempt to twist the arm as it works... That seems wrong...

 

It is obviously not on-car adjustable.. And it may have a greater range of adjustment... but it is still locked into incremental changes... just like everyone else's.... in fact the ball joint will have to rotate in 360* increments... not just half turns like the Heim joint end...

 

If the designer made those claims.. I would not trust his workmanship at all...

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I don't know what tie rod people are using to replace the ball joint, but it looks pretty beefy to me. It looks like it is 3/4" threads, probably off of a big ass truck. I've never heard of anyone complaining about the older AZC arms, FWIW. I do agree about the adjustment; you obviously need to disconnect the TC rod, and you obviously need to go around 360*.

 

The only other comment I have is that there was another thread where it was pointed out that the TC rod itself has the most strength (takes the least side load) when it points directly at the ball joint. If you notice neither of these aftermarket arms has that angle "right".

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The sway bar will attempt to twist the arm as it works... That seems wrong...

 

That's why I dont like these as the T/C rod is meant to to that - take TENSION and COMPRESSION not bending.

 

.... in fact the ball joint will have to rotate in 360* increments... not just half turns like the Heim joint end...

 

Can't you just turn the inner rod end and at least get 180 degree? The outboard adjustment seems pointless to me other than for some reason which I dont understand you want to change the relation of the ball joint vs the T/C rod attachment.

 

Cameron

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You're right Cameron, but in order to use it like a turnbuckle (which one would assume is the point) then you need to move it 360*. You could just pull the inner control arm bolt, move the inner pivot 180 and put it back, but then you're even farther from "on the car" adjustability.

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I was the one advertising the arm kit that jeromio was talking about above. I had made a set for myself and made a couple of extra sets at the same time. The tie rod end is the same one that Arizona Z Car used on the front tubular arm that they used to sell. Its a heavy duty piece off the front of a late model Ford truck. The threaded shank is a 22mm thread, which is over 7/8", so its not a marginal part. Even though there were never any issues with the Arizona Z Car arms as far as strength were concerned, I just wanted a little more beef and used 1 1/4" tubing with a 1/8" wall and welded in threaded inserts. Because it has right hand threads on one end and left hand threads on the other, its much easier to adjust than the original Arizona Z Car arm, which was right hand threaded on both ends. Yes, you have to disconnect the TC rod and then rotate it a full turn to adjust it but that's still amounts to a very minor camber change. I am in the middle of prototyping another arm that will use a female rod end on the inner side, a 3/4-16 jack screw and then a short piece of tubing that will connect the jack screw and the Ford tie rod end. This should allow much more minor and accurate adjustments without disconnecting the TC rod. I'll post pics for comment as soon as I have one put together.

 

Mike Mileski

Tucson, AZ

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I'll post pics for comment as soon as I have one put together.
Looking forward to that. It's amazing to me how many variations there are available for rear arms compared to fronts.

 

If you can keep the price to the $500 range (all inclusive), I will be very interested. I need to buy tires, but I need to get adjustable arms before I do that. I'm very, very close to just buying the AZ arms....

 

I'm also curious to see more discussion/information about the sway-bar mounting on these (and the old-style AZcar). I have zero concern about the slightly inboard location for the TC mount point, but the potential twist from the little lever-arm of the sway bar does seem like it might be a valid issue. The resist is loading the clevis in a twisting (bending) force. Maybe this isn't a problem? I'm sure there's a pretty large installed base of the old AZ design out in the field. Then again, Dave did completely re-design and now has a sway-bar mount that is almost identical to stock.

 

I like the outboard ball-joint for elegance of design and have no concerns about it's ability to handle the load. It's also a more readily available part for R&R.

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