The poor man's rear toe-in adjuster

[240Z2NV]

Thanks for indulging me. Sorry I'm so dense. I'd like to continue our 'discussion' off-forum so as not to put the rest of the community to sleep...but, I do still have some unresolved questions. I will PM you a pic of my R230, and Tim's transverse link design that I copied.

[peej410]

hey, this is a little off topic but has anyone ever considered a modification that raises the inner pickup points? i helped my boss design a modification for porsche 914s that raises the rear pickup points 3 inches. he races in SCCA and he said that after correcting the rear geometry he didnt notice an increase in handling, but an increase in his comfort pushing the car to its limits. i know because of the current design this may be infeasible but i thought id throw it out there anyways

[blueovalz]

I considered it at one time, but the front bushing receiver is integrated into the unibody, making it a great deal of work to raise, whereas the rear would be vastly simpler in that the uprights could simply be shortened.

[peej410]

ive played with a few ideas, but nothing concrete yet. later this winter i might do something about it because i love how low my z sits (which happens to be way too low) so im going to run a taller wheel tire combo all around to raise it up a bit but i dont want to lose that rear geometry. i dont mind custom control arms so maybe ill figure something out. thanks for the input

[blueovalz]

so im going to run a taller wheel tire combo all around to raise it up a bit but i dont want to lose that rear geometry.

Perhaps I did not understand the last post Raising the car with larger wheels and/or tires will not change the geometry of the suspension. Now, if you lower it back down again after installation of the larger wheels/tires, the geometry will change, but then the car would be:

 

way too low

again.

[peej410]

sorry i should have been more clear, as far as aesthetics i like the way the car looks with the tires tucked. i want to run larger wheels and tires because mine only spec out to 23 inches (what i got the car with) which would keep my suspension where it is but lift the car another more than 2 inches by going to a 25.4 inch tire setup. lifting the suspension pickup points would bring the suspension closer to where it belongs stock as far as geometry. overrall id have 5 inches of ride height, which is right where id like it to be. raising or lowering the inside pick up points would effect the camber gain and other geometry but not really the ride heighy because the struts would still mount in the same location, utilize the same springs and still work overrall in the same manner

[jeromio]

Back on topic: I pondered the crooked-ness. I measured the spindle pins and I show about 1/4" of toe out. So, I guess I have bad strut machining.

 

A new strut will be dollars plus much extra work. Good chance that the "new" strut will be just as bad too. So I re-removed the rear link-up (short-hand for the whole rear uprights plus adjustable transverse link), ground out the upright arches. I also ground down the inner part of the crossbar and the edges of the threaded tube of the turnbuckle to allow for as much crank as possible - painted, re-installed. I thought I had allowed for the amount I needed - about 3/8 inch of adjustment plus an extra 1/4 of movement to the driver's side to correct for slant. But apparently not. I had it close before it bound up, but the thing was too tight. The driver's side bolts wouldn't tighten - slightly crooked from being tweaked past the ovals. The transverse rode up on the new arch of the transverse and skewed the holes.

 

So, it's all gotta come apart once again. I've got it down to about 1/2 degree toe-in, which is probably fine, and 1/2 degree of slant. I just need to be able to lock it down. It's only the lower edge of the arch of the upright that interferes. Trial and error - it's a way of life.

[buZy]

Sweet Design!

[jeromio]

Wow, this thread was hard to find.

 

Anyway, I finished up getting the alignment as close as I could. I knew it was still off because I have the adjuster cranked all the way (as short as it can go) and I cannot push it to the driver's side any further (without ovaling the holes on the pass side to the point where there's no more metal).

 

So, I took it to the local alignment shop (also got it inspected - first time ever). I told the guy that they wouldn't be able to adjust it and just to check it and charge me whatever a "check" costs. Well, he apparently tried to align it anyway. Of course he failed, and then wouldn't charge me anything. Oh well.

 

So, I have the following specs:

 

left right

Camber -1.52 -0.85

Toe -0.51 +0.41

 

Total toe -0.10

Thrust angle -0.46

 

So, this is an actual improvement - can you believe that? I have almost no toe. Now, obviously it is still completely deranged and I am very discouraged. I have a diagonal car. I figure I need to move that passenger side over another 3/8 to 1/2 inch. That would then allow the driver side to move over that amount also. That should bring camber a little closer, but it will still be hanky - driver's side will have more. Those camber values really underscore the situation: I'm having to crank the entire bottom end of the suspension over to the driver's side to make up for some really screwed up parts. I am presuming that I am the victim of a messed up strut on the passenger side.

 

So, my plan, such as it is, is to take everything apart again and oval the top holes on the upright(s). I think I will also have to cut the cross brace off of the pass. side upright, grind off 1/4 inch or so, and weld it back (narrowing that whole structure). Then I will put it back in and shove that whole unit over to the driver's side. Then I'll put it all back together and line it up.

 

Now, after all this, assuming I can get the toe and thrust angle sorted, I will still have screwed up camber. If I have to add 1/2 degree of negative camber, is slotting the holes on the strut top going to be sufficient? I don't want to lay out $300 for camber plates. Possibly I could balance it out, slot to the outside on the driver's side and the inside on the passenger side and end up with maybe -1.2 on both sides. On the front I have -2.5 and -2.1, which is a bit much, but I think -1.2 on the back would be fine, no?

[blueovalz]

It sounds like you've got a good grasp on what needs to be done to get this perfect. Thanks for the update.

[JMortensen]

Jeromio-now might be the time to consider some G Machine bushings in addition to the poor man's toe adjuster. Until you get that thrust angle right the car is gonna crab down the road...

[JMortensen]

So here's what happened. I saved up some money and bought a sway bar. Turns out it wasn't going to work because it attached to the stock uprights and the transverse link. So I sold it and bought the ST rear bar. Spent a couple hours yesterday slotting the holes (PITA when all you have to work with is a dremel).

 

Now since I have a hellacious case of the while I'm at its this time around, and I shimmed up my LSD and katman says that shimming it will make it run hotter, I would really like to get this all done with the 300ZX finned cover on the back, which makes the transverse link part much more complicated. I bolted the finned cover to the mustache bar and found some surprising stuff.

 

1st, the diff isn't centered in between the uprights. I guess I already knew this since I knew that the stock halfshaft was too long on the driver's side, but I hadn't really visualized why.

 

2nd, the ST sway bar clears the finned cover nicely. There is about 1/2" clearance as it is, and following the John Coffey "space the bar back away from the uprights" edict I should have plenty of room there.

 

3rd, the transverse link looks to be a big PITA. I really need some ideas on this one. I'm struggling with how to get the turnbuckle out far enough away from the cover, but still have some strength. So far I've had one idea, I'm looking for some feedback here. I could get a piece of 1/8" bar stock that is as tall as the transverse link (1 1/2" or whatever it is). Then cut the link on both sides as close to the bushing mounts as possible so that they aren't likely to interfere with the cover. Then I could weld the bar stock to the link so that it juts straight out behind the diff. I figure if I JUST did this, the link itself would be very flimsy. I know that it is bolted to the uprights, but still, that level of flimsy makes me uncomfortable. So I'm thinking that I could add a triangular brace along the top to meet up to the curved part of the link. I've done some photoshop work to give the idea, it's not the best (I'm envious of Terry's skills).

 

What say you? Yea, nay? Any better or simpler ideas???

[JMortensen]

I think I found 2 possible answers.

 

ZR8ED has this which basically looks to me like my drawing without the braces on top.

 

Then I searched through some pictures that I had saved 2 years ago in preparation for this, and I came up with this picture:

This looks like just what I had envisioned originally. I tried laying some 1" square stock under the angle on the stock piece, and it fits, but doesn't fit with the bushing and the big washer on the back there. Maybe I could just trim the bushing and the washer??? I'm looking for the owner of this car to ask what they did about it. If you know whose it is, PM or post please...

[JMortensen]

More progress. First I cleaned the garage for about 5 hours. Amazing what a mess I can make... anyway, I worked on two things today. I welded a piece of angle iron between the uprights up at the top. This came off pretty smoothly. The hardest part about it was trying to get everything lined up. I measured the distance between the uprights and cut a piece of 1 1/2" x 1/8" angle iron to fit. I tried to lay on my back under the car and hold the piece up there to tack it in, but I just couldn't seem to get it lined up. So I pulled the uprights back out and realized that they are 3/16" thick, and my angle is 1/8", so there's the problem. Duh. So I set them on the edge of my workbench and clamped them all to the edge upside down, so that the top would stay flat. Then I tacked them pretty good, put it in the vise and welded it all up. Done. I think that piece is going to add a lot of structure to the uprights, so I'm glad I did it.

 

Then I started in on the link. I used my 1" square stock and cut the first pieces to come off of the original link ends. I cut them at a 30º angle and 3" long, which gives me about 2" clearance behind the uprights. That should be enough to clear the cover. I tacked them to the original parts just to see how this is going to end up. Here are some pics.

I don't like the way the square stock sits so close to the bushing cup. I think I'm going to grind all the tack welds off and then cut a slot in the angle at the top of the original link, and weld this piece right into the angle. It would give about 1/8 or 3/16" clearance between the bottom of the square stock and the bushing area.

 

The plan is to connect these two pieces via some tap tube and some old rod ends. This was my old rear strut bar:

I'm going to weld in a new solid bar based on info from a thread with Drax and John Coffey, so I figure I'll cut the ends off of these rod ends and weld them in the square tube ends, then cut the tap tube and retap it at the needed length to make the turnbuckle.

 

I still need to make a plate to go here to hold these bolts from the back.

[blueovalz]

Glad to see you working on this project again Jon. I know you wanted the turnbuckle as close as possible with the plane of the link(s) mounting surface, but this should work fine as long as the bolts are not loosened to much when you make the adjustements. That way, the torque applied (this far off the mounting plane) will not distort or "bow" the new link assembly during the pull/push the turnbuckle creates during adjustments. Then when you cinch down the bolts after the adjustment is made, you've eliminated any small changes created by re-staightening out the link. You will be quite happy with this when finished. If it was not for the link I made last year, I'd never be able to "experiment" with various rear toe settings, and I have been quite surprised at how little adjustment is needed (as small as 1/2 turn - I'm using coarse threads) to change the character of the car (perhaps these wide tires amplify the toe issues). As obvious as it was, I failed to realize that 1/2 turn on a turnbuckle is equivalent to a full turn of thread pitch in regards to the bushing movement (the turnbuckle pulls/pushes on both threads at the same time). Over the 18" span of the bushings, a course thread 1/2" bolt (13 TPI) was equivalent to a toe change of .49º / 1/2 turn (no calculator here, just going on what I think I remember from last week). I'll quit rambling and ask for more progress pics when they come available.

[JMortensen]

Well I blew it today! I welded up the sides of the link. I had checked it, tacked it, then welded it all up. Be the time I was done welding it it was WAAAAAY warped. I guess this is how I learned exactly how badly things warp when you weld them. So tomorrow I've got a hell of a lot of grinding to do. I'm going to make the link one whole piece, instead of doing each side separately. Then I'll cut it, and then weld the rod ends in. Kinda bummed at how bad it went, but I think I can salvage the part. Even if it's totally screwed, I'm sure I can get a link from somebody on hybridz and start over if need be.

[blueovalz]

That's what doing something no one has ever done is all about. Even doing it in one piece will present some minor warping. You will find (as I did) that when the welding is done on the single whole link, when the piece is cut in half, that it will "boing!" into place slightly differently than prior to the final separation. It's the nature of the beast when you weld. Just keep the filler material buildup to a minimum.

[JMortensen]

lol "filler material buildup to a minimum". I was thinking "I'm gonna weld this sucker GOOD!!!" : Just means that I'm REALLY gonna learn this lesson.

[blueovalz]

My take on all the stresses these parts take is this. Lateral loads on the rear suspension are taken predominantly by the rear bushings because the axle centerline is closely aligned with this bushing. And these lateral loads are kept in check with the two bolts holding the uprights to the subframe. If we could insure that these two bolts could never become a failure point, then the need for a transverse link would be unnecessary, but Datsun wisely reinforced the uprights, located near the bushing location, with the link, which then distributes the lateral loads between two uprights (or four bolts) instead of one. With the welded tie bar that you've used to tie the two uprights together, you've gone in that direction, which then reduces the requirements for the distribution of loading to pass through the transverse link (thus making the new adjustable transverse link strength requirement less and less important). Obviously, the wider, and the lower (in location), the welded bar/rod/angle is located on the uprights, the more effective it is in distributing the lateral loads between the two uprights. I've not seen the welded bar between your uprights, but I'd make it as wide (and perhaps gusset the ends) as is permissible with the rear cover you're using. Just some things going through my mind at this time. For me, I'd like to know that I would not need to depend on the adjustable link for supporting lateral loads if I could somehow get away with it, and have it used as simply a means of moving the bushings left and right as needed.

[JMortensen]

Thanks for that Terry. Kinda puts things back in perspective a little. I think putting the angle across the top is a good idea because I've heard of several racers who have had failures where the uprights bolt to the frame, and by connecting the two uprights the "footprint" of the piece that now takes the side load is much bigger. I had thought about some gussets too. Maybe I'll make some.

 

I think you're right that having the link bolted to the bottom does mean that the turnbuckle doesn't need to be quite as burly as I've been thinking, so that is helpful. Sometimes I go a little overkill on this stuff. I think I've figured a way to make the construction of the link a bit easier too. Had plenty of time to think about it while I'm grinding away...

 

Cut the whole angle off the top of the link. Weld the square tube as before, except without warping the crap out of it this time. Then make a small gusset to weld in between the upright and the inside of the tubing. The advantage here is that I don't have to cut the slot in the angle to make the square tube fit, and on the outer end I might be able to put a couple marks so that I can know where 0 toe is. Might be that the marks are too close together based on your comment from yesterday, but it would make the job of welding everything easier today anyway...

 

I appreciate the feedback.