Reversing UCA's (Pics)

[The Roadie]

For me, flipping the UCA fixes some negative camber, but it can't all be aligned out unless the UCA was longer or I machine the LCA mounting bracket holes to allow it to move inboard. It's a natural result of the UCA being shorter than the upper. Very odd that you have any positive camber at all being lifted.



Your observations about the tie rod pivot point are fascinating, but I don't see them as tied to the UCA flip. Have to investigate for sure. Thanks!

[fishsticks]

So the problem is finding out the actual dimensions of a suitable short outer end. The Moog spec only gives you part info. Anybody else have a source for the tie rod end dimensions or has some one identified a short 16 mm outer that matches our spindle with or without the need to reamer the spindle?

Thanks,

Ron

Ream the knuckle hole straight and run a heim with misalignment spacers.


Like the others who responded, I've never noticed this problem either. As long as your tie rods are roughly parallel with the LCA this shouldn't be happening.

Pics from behind of your front suspension? (from the back of the wheel well if possible)

[fishsticks]

I just reread your post and noticed one more thing that needs to be brought to your attention.

To strengthen the tie rod, I would bump the rod size to 16 mm expecting to match up a male heim with a male outer tie rod end through an adjustable straight tube with weld in left and right hand thread tube adapters.

Welded steering is not DOT approved for highway use. You'll want to use a solid piece of DOM with threads tapped internally. You can usually get these from offroad fab shops. 1.25" DOM tapped may allow you to run Toyota FJ80 tie rod ends, which I BELIEVE have the correct taper (I'll look).

All of this is going to be very strong. Maybe too strong... you may make the rack the weak point in the system.


EDIT: I lied about the Yota TREs. You would need to ream out the knuckles quite a bit.

[Lauron]

Roadie, I followed your comments about the suspension and negative camber but this is not what I have experienced. If you look at JamesDowning's pics showing the UCA stock and reversed you can see the ball joint is farther out. So with out pushing out the LCA, there has to be positive camber.
Right from Fishsticks first experiment to try this, he had positive camber. So it seems to be consistent and makes sense to me. Maybe mine was more pronounced but saying this I am living with it right now. But I am obviously very concious of the bump steer I am getting.

Attached is the current pic. Hard to tell that anything has changed. What was really revealing to me was the change in toe in when I flexed the suspension.

The bds drawing and discussion may help. The principle is the UCA, LCA and Tierod must line up at the instant center with the outer and inner pivot points also lined up to avoid bump steer. With unequal length arms, I believe zero bump steer only happens at one position over some range of travel, not full suspension travel.

So, if the LCA is moved out, the inner tie rod end needs to move out as well. Of course the outers are not moved from their alignment.

As far as selecting an outer tie rod, I do not want to go with an unsealed heim. Inside I hope to have the heim and clevis fit inside the existing rack boot.

Fishsticks, thanks for the warning on the welded ends. I can get the DOM threaded and cut a few wrench slots.

Always a good idea to build in a weak link that is cheaper to replace than the expensive pieces, the rack or pinion. The rack seems pretty stout so what has broken?

I will identify 16 mm TREs that are closest and go to my neighbourhood parts store and ask to measure them. Will advise what I find.

Thanks,

Ron

[v7guy]

Through a full cycle of the suspension I can definitely see how toe in would happen at mid compression and then as the tire was stuffed it would pull toe back out to "normal". I think the reason a lot of us don't see any difficulty with the handling is because we've ended up making the front end stiff enough that it doesn't have a lot of up down movement in the real world.
It also may be that your paticular truck has the tolerances all at the wrong end of what GM builds as acceptable so your alignment can't meet the specs of what many of us have been able to get. Have you posted what your alignment ended up at?

I haven't had any of the trouble you mention, but I can definitely say that driving a lifted truck with big ole sidewalls/treadblocks took a bit of getting used to

[Trail X]

What was really revealing to me was the change in toe in when I flexed the suspension.

The bds drawing and discussion may help. The principle is the UCA, LCA and Tierod must line up at the instant center with the outer and inner pivot points also lined up to avoid bump steer. With unequal length arms, I believe zero bump steer only happens at one position over some range of travel, not full suspension travel.

So, if the LCA is moved out, the inner tie rod end needs to move out as well. Of course the outers are not moved from their alignment.

Did you measure your change in toe in during suspension flex? Conceptually I certainly understand it, but I don't know if I'd be able to visually see a change of one or two degrees.

The BDS drawing is correct for proper driveability, but it could still affect toe at extreme levels of flex... but you're not really concerned with that when you're flexing, you're only concerned with bump steer when driving highways really.

Your logic of moving the inner tie rod out is potentially sound in order to retain a close-to-stock steering geometry, but I'm not convinced that these small changes will make are really that big of a factor. I just did a very quick 2D layout comparison using a rather rough lifted IFS suspension layout. I varied the length of the tie rod and the length did not seem to contribute significantly to the change in toe numbers during moderate suspension cycle. I was using a 5 degree suspension compression for my numbers, which may be more than is experienced on the highway.

Before you go making expensive changes, get some data first. Record the toe in change through the suspension travel with the UCA flipped and not flipped. See if it's significant. Concentrate on the +/- 5 degrees around the normal ride height.

[Lauron]

To measured the change, I bolted a straight stick horizontally to each of the hubs and measured the distance between drivers side to passenger side front edge and rear edge of the brake disk. To keep the measuring tape straight I used a level from the stick down to a constant height. Since the wheel(disk) moves in and out with travel the change in front to rear provides a distance change to calculate the angle change over the disk width (13.5").

I know this is definitely something I should have gotten a picture of. I will do it on the next check.

A little trig (arcTan) and the compression of 2" caused a 2 degree toe in change and the up travel of 5 1/2" resulted in just under 5 degrees toe out. As a check this was 1.6" of front to back total change at the disk edge.

A total of 7 degrees change was obvious to see with the 3' long sticks I was using. So for highway travel 1 to 2 inches of travel results in 1 to 2 degree of change in toe angle. Too much and noticeable to drive on the highway? Anybody know if this is significant or not?

This was with the UCA flipped. To return the UCA back to stock, I would have to realign the LCA before I could re-measure toe changes.

So, I am thinking a can build a plastic or aluminium spacer to thread the inner tie rod end into and then into the rack to test/confirm the theory. This could avoid a premature build if this did not work.

I do not have the alignment data right now. My son did it and said everything was in spec except for the caster. I will get them this weekend.

Spacer to come.

Ron

[Trail X]

I followed your setup and measurements. Glad to hear you did the footwork.

Check your math - you said 5 degrees equaled 1.6" of change, but my math shows that 1.6" of change = nearly 7 degrees.

Now, a clarification - if the suspension is cycled up, does that create toe IN? or out? Toe IN should theoretically combat the effects of wind, right?

Your proposed test could definitely test your theory. It would be interesting to compare the results, but I would suggest that you also retake your 'as is' measurements again before you put the spacer in.

Bigger than toe issues, I'm curious where your caster is. Caster plays a rather big role in highway stability.

[navigator]

JD, I would call caster front/back lean and camber in/out lean.
I'll admit I don't understand all the dynamics of it but I wouldn't think caster to be too big of a deal compared to camber.
It would seem camber would affect how much tire touches the ground.

After flipping my UCA everything came back in spec for me except caster as well.

[fishsticks]

Your proposed test could definitely test your theory. It would be interesting to compare the results, but I would suggest that you also retake your 'as is' measurements again before you put the spacer in.

Bigger than toe issues, I'm curious where your caster is. Caster plays a rather big role in highway stability.

And caster is notoriously difficult to to get in spec on lifted 360s...

[fishsticks]

JD, I would call caster front/back lean and camber in/out lean.
I'll admit I don't understand all the dynamics of it but I wouldn't think caster to be too big of a deal compared to camber.
It would seem camber would affect how much tire touches the ground.

After flipping my UCA everything came back in spec for me except caster as well.

Think of a shopping cart with a retarded wheel when you think of caster being out of spec. It wobbles all over the place.

Caster is what keeps the wheels "wanting" to go straight. Best layman explanation I can think of.

[HARDTRAILZ]

I think of caster as rake on a motorcycle.

Most vehicles are not sensitive to caster changes but too much on a big lifted truck will make it harder to steer.

[Trail X]

I think of caster as rake on a motorcycle.

Most vehicles are not sensitive to caster changes but too much on a big lifted truck will make it harder to steer.

As I understand it, too little and you'll get steering that doesn't want to straighten (like driving in reverse (negative caster)). Too much, and you can get a car that will tend to steer down a crown or be easily pushed by a crosswind.

[Trail X]

JD, I would call caster front/back lean and camber in/out lean.
I'll admit I don't understand all the dynamics of it but I wouldn't think caster to be too big of a deal compared to camber.
It would seem camber would affect how much tire touches the ground.

After flipping my UCA everything came back in spec for me except caster as well.

Camber is really only an issue for tire wear, given that your camber is symmetrical. Asymmetrical camber could do some strange things.

[Lauron]

James, our numbers are consistent. I have a total of 7 degrees of change. 2 degrees toe in on extension(down) and 5 degrees toe out on compression(up travel).

On the highway, if I get a single wheel bump or a push(wind) to one side where one wheel is compressed causing toe in, I get a dart of the vehicle to the opposite side. With equal compression, there is no darting. Everything is stable because both wheels are opposing each other with more toe in on both sides.

As far as caster goes, I definitely have less caster. I do have to assist the steering to come back to center after a turn. This occurred both with stock tires and the wider wheels and tires.

I confirmed with my my son that he just pushed the LCA out. He did not try to adjust caster because camber was more important. But he agreed there was some movement still possible to twist the LCA but not a lot

This weekend is looking very busy but as soon as I get to it with a spacer, I plan to take a movie of the suspension travel so all can see the change in toe in. And of course hopefully the spacer will prove up the solution.

Ron

[v7guy]

I still am anxious to hear what your alignment specs are. The toe data is nice, but with no base spec the information is rather skewed. A data point to start from that you have on your truck and that we can compare to our trucks would be very helpful. Frankly I'm surprised I'm the only one asking for this. Comparative analysis with your setup and ours could be really helpful and even if your specs are the same as ours I don't think anyone would be less interested in your findings. Even if an inner tie rod spacer makes the difference, the part would be cheap and strong. A lot of people would be on board if it helped driveability.

In my experience playing with alignment on the ole firebird with 18x11s on the front. Castor brings the steering to center. Especially at highway speeds. The more castor the better. This will obviously come at the expense of heavy steering. But generally more castor is good. It helps stability.
Negative camber is good on a heavy muscle car that's pretending to be a sports car. But this is largely due to heavy cornering from a heavy car gives you a better contact patch. The tire is going to be flat while cornering. On our trucks with flexy sidewalls and big treadblocks I view camber as only causing more tire wear on one edge or the other. Neutral is probably better.
Toe I played a lot with. Toe out in any fashion generally caused unpredictability. I suspect the same on our trucks. Even with the toe neutral at zero the car was very darty. I suspect that with zero toe on our trucks it would feel pretty good, maybe a bit of negative toe would be nice. 0 toe to 1/16 toe in made a massive difference in the car. But we're talking about a lot of flex with squishy sidewalls and big ole treadblocks. I would think that a lot of it would be absorbed by momentum and the flex of the sidewall.
The actual flex of our suspension that we typically top out on a regular basis and have a 1/2 inch of down travel on makes me believe that our real world experience is a massive difference from the theoretical suspensions travel/toe change.
Just for shit grins and giggles, and because I can move off my couch after surgery, I'm going to measure my extension and see where I'm at with my super shitty extreme 89 springs with the 3" lift.

There's been a lot of questions as to my measurements and I'll post em here. I've posted my alignment specs previously. I'd like to see you do the same, I think the community could gain from our info.

From a real suspension geek (I'm on the verge of spending for a cortex spindle and LSA for the firebird to improve the handling). I'm really interested in your current specs and the possibilities. Lets hear some base number to go from.

[HARDTRAILZ]

You nailed it...no one is asking because no one else lacks drivability. We are interested but it seems to be a random problem being that so many have flipped without issue.

[Opeth]

Maybe this will help...



My current alignment. We kicked the LCA's out as far possible, then moved the outer TRE's out 1/2" either side. Prior we marked where the camber was good and started backing the TRE off to check how much thread was left inside. There is more than an inch of threads grabbing in the inside, more than enough for me to feel comfortable. I have no ill effects while steering, except I didn't trim enough fender liner yet. Still rubbing on rocker panel trim in reverse I think.

3" lift, flipped UCA's, stock springs.

[Lauron]

Been a while sorting out a solution.

First my alignment specs were:

Camber -0.72, -0.61
Caster -1.85, -1.95
Toe in 0.1, 0.1

So caster was out of spec and I hope to have it corrected or at least improved with the next alignment. We only pushed the LCA out.

As I previously suggested, I was getting bump steer while most of you did not have a problem. I cannot explain the difference but once I saw it, it was significant . The first pic is the way I measured the amount of toe change. I measured from the stationary strings to the marked board(front and rear edges of the brake disk). It is not real accurate but did direct me to the solution.

The chart shows the toe change for 4 configurations:

1. Stock is with the flipped UCA where I felt the bump steer.
2. 2 cm shorter would have been the solution of using a spacer between the inner tie rod end and the steering rack. This was the solution I thought would work because the UCA was moved out about the 2 cm. To my surprise minimal improvement.
3. 6 cm longer - so now I started the trial and error search. I could have tried to draw it up but this was easier. The longer tie rod would have meant shortening the steering rack - not a nice solution. Fortunately it didn't work.
4. Ultimately, I found lowering the outer tie rod end gave improvement and I landed on a 35 mm drop of the stock tie rod. The Lauron tie rod is presented in the chart and is shown in the last pic.

The solution is a Q1A 3/4" female greaseable rod end with 3/4" Seals-It seals. This rod end has 24 degrees of misalignment. I calculated I needed 21 degrees. To lower the rod end I machined a 3/4" tube spacer 40 mm long. The Q1A rod end is narrower that the stock end. This spacer caused the heim to only achieve 15 degrees of mis-alignment. In hind sight, a bigger rod end with misalignment spacers down to 3/4" could be a solution. Since I had these, my fix was to bend the rods.

The rod is 3/4" 4140 rod threaded to 3/4" fine for the Q1A end and 14 mm fine for the stock inner tie rod end, both right hand thread. I had the rods bent to just over 8 degrees to get back to approximately 24 degrees of misalignment on the downward extension of the suspension. No binding with compression of the suspension.

I have only driven it once but the bump steer is gone.

Concerns: lowering the rod end will increase bending on the spindle and the 3/4" grade 8 bolt and spacer clamping on the rod end inner ball face could loosen up and wear. So I will have to sort out high high I need to torque the 3/4" bolt. I do believe the outer end is far stronger than stock so the inner tie rod ball end will be the weak link. Time will tell.

So I do have a request of the members if your are pulling your front springs is to cycle your suspension and measure the amount of toe change. If I would have know it, I would have measured the stock change but I can't go back now.


My current distraction is I am building an aluminium rear bumper and tire carrier.

I hope to do some good road testing of he TB over the Christmas Break.

Merry Christmas,
Ron

[Lauron]

Lauron Tie rod installed.