Reversing UCA's (Pics)

[Lauron]

Sorry a small but obvious missing in my description, I had to drill out the spindle to 3/4"

Ron

[The Roadie]

Ron, I'm drooling over this project. Thanks for the write-up. Will try to duplicate your measurements. How again did you move the LCAs around? Mill the slots larger?

[Lauron]

Recall I had positive camber so all we (my son) did was to push the LCA out. There is some slop in those slots so to angle the LCA to correct the caster is what I recall others were able to do. I am not sure how much is available without opening them up as you suggest but we will see.

Ron

[v7guy]

I know guys bend their steering arms for clearance sometimes but all I can think is that the rod is essentially pre-failed.

In the "fixing my steering" thread I posted up a heim coversion piece. I never updated my work on it but I found that after I chucked up the heim conversion piece up in my lathe and turned down the ridge it did actually fit. All you would need after that is some high misalignment spacers to get the angles you need and you wouldn't need to bend the tie rod. Just a thought.

You can find the link to the thread here.
viewtopic.php?f=32&t=2510&hilit=Fixing+my+steering&start=80

[Lauron]

v7guy
Bending the rod is plastically deforming the steel but fortunately, like most steels, it will tolerate some if not a lot of yielding before reaching ultimate tensile strength and cracking. The amount of deformation here is low so I am not worried about cracking. The other failure concern with bending is buckling. The rod took over 3000 lbs to bend in a ram press. So buckling is unlikely.

You mentioned turning down the ridge on the heim. This was the same interference problem I tried to solve by milling a 45 chamfer on the bolt head and the spacer sleeve. It did help but not enough. The 24 degrees quoted is interference on the 3/4" bolt. But using a misalignment spacer requires the use of a smaller bolt with a contact on the misalignment spacer of 3/4".

My concern with this design is bending the bolt so I would not go below the 3/4" Grade 8 bolt just yet. With out confirming the misalignment spacer size you would probably have to move up to about a 1 1/4" heim which could work assuming you could mate up the rod end as well. My problem was I bought the 3/4" heims and bending was a simple fix to prove up the dropped design.

Next design I will certainly investigate the bigger heims.

Ron

[v7guy]

I mentioned turning down the ridge on the heim conversion piece, not the heim. It shows the piece in the thread I linked.
I bent the tie rod. Granted, it was by contact with the spindle, and I have no idea the loads it saw, but it still bent. The guys in the 2500/3500s are breaking/bending them pretty frequently as well.

For the lazy

[Lauron]

Hey Jason, I did recall you drilling the spindle and the bent tie rod but I didn't pick up on the fact you turned the heim conversion. Yes you do need to give the heim room to move.

You bring up a good point - if the rod is going to bend when installed it is going to bend in the threaded section. My pre-bend is in the shaft section because we positioned the rod in v blocks inside the threads when we bent it.

In use, the highest bending load will be on the outer end but I still see the 14 mm inner end as being the weak point. An alternate inner tie rod end like CST's may be the next version with a tube tie rod.

131_1205_03+ifs_strength_and_safety+steering_joint_comparison.jpg (5.86 KiB) Viewed 67596 times

If the 2500 tie rods are bending then the obvious needs to happen - go bigger or stronger. I suspect the rod material has a 30 to 40,000 psi yield strength. Could be higher if it is heat treated. 4140 has 60,000 psi yield, so I am hoping this is enough. I guess I need to go and do some field testing to find out what breaks.

[Lauron]

On my previous alignment, we only pushed the LCA out to correct the camber. I would like to correct the caster, currently at -1.85 and -1.95, to the positive spec. Before I take the TB to get it aligned, I was wondering just how much caster correction is possible with the stock LCA mount. From the discussion, it sounded as if most could not get back to spec even if the alignment shop knew what they were doing.

How again did you move the LCAs around? Mill the slots larger?

Has anyone milled the slots in the LCA mount bracket to increase the caster adjustment? Which holes? How much was milled and how much increased caster adjustment did you get over the stock range ?

Ron

[Lauron]

Guys,

I am finding out that some of you who have flipped the UCAs are accepting either negative caster or positive camber because there does not seem to be enough adjustment in the lower A arm mount to get both correct.

I did not get a response to my last email so here is what I know and propose as a solution.

1. The rear dual holes in the lower mount are too thin to mill any significant amount to increase adjustment. I calculate I need to move the lower mount at least 5 mm forward to change the caster from -2 to +4 deg.
2. The bushing pivot ends are quite beefy, so some material could be removed from their ends with out risking a failure.

My proposal is to press out the bushings and re-install with 6 mm (1/4" ) spacers to shift the A arms forward. The large front bushing only sticks out 7 mm on the inside so it will be tight with the A arm. I will probably need to remove some material from the inside edge of the lower mount pivot to ensure the lower mount does not touch the A arm. The rear bushing has greater off set so it will have less of a contact risk. The rear bushing will have to be installed from the opposite side (the inside). The attached composite picture shows where the spacers would go.

Anybody see a problem with this?

Thanks for you thoughts,

Ron

[The Roadie]

I like your plan a lot. Might be something I can do with the press and milling machine at work.

[Trail X]

I don't like either option very much. It'd probably be fine either way, but it feels like a big band aid. If you're going to go through all that work, instead make new ucas and that way you also fix a failure prone* part.

*ok, maybe failure prone is overstating it, but we have had two reported failures... given our small population I think that's significant.

[Lauron]

James, can you point to and describe the failures? Experience is always the best design tool.

Thanks,

Ron

[v7guy]

James, can you point to and describe the failures? Experience is always the best design tool.

Thanks,

Ron

I'm reasonably sure he was talking about the upper control arm failure, not the failure of your idea or of the lower control arm bracket.

I believe he is probably right. At the end of the day, even flipping the upper control arm is a band aid. Your proposal is equivalent to putting gauze over the band aid. lol That's not to say it's a bad idea, but i think we really need a new upper control arm with a fixed upper balljoint angle that puts the upper ball joint neutral at our lifted ride height. If that was done and all other measurements were stock I think we'd be good. Then the tripot would become the next weakest link.

[HARDTRAILZ]

Far more CV failures than ball joint... I think efforts are being put on the wrong part.

[Lauron]

Jason,
re-reading yes I see James was referring to UCA's. Thanks for pointing it out.

I do agree building an improved UCA could solve the problems. But until we get that built, band aids are what we have or flip the UCA's back.

I for one would like to find a solution and the lack of caster re-centered steering is something I would rather not live with. The debate is then are the modifications more dangerous?

[HARDTRAILZ]

I don't notice any steering issues and not flipping the control arms is going to be more dangerous since the ball joint is at a far worse angle.

[v7guy]

I don't notice any steering issues and not flipping the control arms is going to be more dangerous since the ball joint is at a far worse angle.

I didn't either, my alignment is stock, but it appears Ron is having issues. I'll take what we can get. Nobody else is actively working on our front ends.

[HARDTRAILZ]

My caster is barely out. Definitely not enough to worry about. I think a tenth or two at most.

[fishsticks]

I need to see if I can dig out any old alignment sheets. I think my caster was just BARELY out as well, definitely not as much as Lauron's.

It's admirable to see him working so diligently on this though. Hopefully it benefits more people out there.

[Lauron]

Adding the spacers was a little more complicated than expected and I did not get the result expected.

First, the rear bushing is stepped so to install the bushing from the inside direction required milling the step out of the mount. Not a big deal but then it is only tight on the inside edge. So I epoxied the bushing into the mount.

The finished product shows the the 1/4" spacer on the large bushing (front) and the 1/8" spacer on the rear. This results in the same bushing position as stock but both bushings are now offset by 1/4" forward. This should have resulted in a 6 degree positive caster improvement.

The TB actually drives better now. The steering is easier to return to centre and a previous pull is gone. But the caster is worse
From the previous -1.9 caster we could only get it back to -2.63 and -3.1. So we lost ground.

I am baffled. Either the previous alignment numbers were bad which adds up because it was harder to return the steering or something else has changed?

Anyone have any ideas what else could cause a shift in the LCA position? The ball joints and bushings are tight.

Ron