Rear Spring Plates

SVKarl · 03-12-2007, 07:21 AM

Have not posted before but certainly have learned a bunch over the last year or so. Based on reading as many threads as I could find I decided to replace the rear spring plate bushings with ER poly bronze. Disassembly went fine, removed old bushings with the heat and fume method, cleaned everything up, installed new bushings, pulled out the torsion bars, etc. TB looked perfect, splines and paint looked as new. Re greased them reassembled everything. So far I have re indexed four times on the left and three on the right, working toward 241/4-inch on the fender lips. Here is the question. As it sits now I am at 24 5/16 on the right and 23 15/16 on the left but to get this far the right spring plate, when completely disconnected from the trailing arm almost exactly lines up with the connections on the arm but the left side is probably four or more inches below the connection holes in the arm. To connect the left side I use the floor jack to raise the plate into position. Is it reasonable that there would be that much "fatigue" over the years? Is this typical; can't recall seeing this issue discussed in the threads I've read. (I am aware of the search feature). Seems to me having so much difference means effectively different spring rates from left to right because I need to "pre load" the left side to install. Again, both TB looked perfect, not even a mark on the paint, no rust, nothing. I got the correct bar on each side, L/R. As I recall the right one was not only stamped R but the end was green, I think the left one was white on the end, stamped L.

Car is a basically stock 84 Carrera Targa, 108k, always in the northwest so no rust anywhere. I know photos are required but need the combination of clean car and nice weather for a photo and that's difficult to achieve here.

Thanks again for all the education

Karl

ZOA NOM · ZOA NOM's Garage

First, welcome to the board, and congratulations on tackling the t-bar mess. Do a search for Wil Ferch, and his angle calculator. It will give you some good info about making accurate adjustments to the ride height. Both sides should droop at very close to the same angle, when disconnected from the trailing arm. Also, there are splines on both ends of the t-bars, and you must turn the bar one direction to set the inner splines, and the spring plate/t-bar cap the opposite direction to change the outer splines. The combination of these opposite movements will change the droop angle in very minute degrees.

Grady Clay · 03-12-2007, 07:31 AM

Karl,

Welcome to the Forum.

You will find a lot of help here.

Good for you doing your homework (Pelican Searching).

When you find you can’t get one bar correct, try moving the inboard splines 90° and try again. There also is a program linked on the Forum (I lost it in a computer crash) that will get you there.

Best,
Grady

SVKarl · 03-12-2007, 07:37 AM

Thanks Zonas, read up on the calculator and understand the reindexing program with respect to the spline differences. One combination of turns seems to move the plate up or down about a degree (50 minutes) or about a quarter inch at the trailing arm end of the plates. My question really is that as I close in on the ride height I am looking for the relationship between the unloaded plate on the right side is nearly lined up with the trailing arm connections while the relationship on the left side is about four inches lower than the connection locations on the swing arm. I am wondering if after this many years that is typical or what.

cbeers · 03-12-2007, 07:37 AM

I second the angle calulator method. I had those pages marked as favorites as I just got done with a suspension refresh/rebuild as well. Go to Home Depot etc. and get a $20 angle finder. Use this to check the angle of the spring plate at full droop. Once you start messing around with the Tbars, you'll see how changing the spines, inner/outer/both, affects your height. Then work at it until you NAIL the angles on both sides. One side took me several tries before getting the exact angle (well, as exact as a $20 finder can get). Buttoned it all up and took it in for a corner balance/alignment and ride height. The tech barely had to adjust anything at all. It was pretty darned close.

The angle calculator page and the angle finder are golden for this.

I hope that helps

-Chris

cbeers · 03-12-2007, 07:43 AM

Just read your follow up.

First, I have to ask the obvious, are both shocks disconnected? Good

Ok. On my car, both side were higher than the disconnected trailing arm. I did as you did and used a small jack with a block of wood to lift the trailing arm into position. I slip in both eccentric bolts and finger tight the nuts. Then I get one bolt into the trailing arm and finger tight the nut. Often, the other holes won't line up well, but since the eccentric bolts are in place, you can use those to position the trailing arm into place. Slip in the remaining bolt and you are on your way.

One last thing. When checking for SP angle/droop, be sure the lower torsion bar cover plate bolt is removed.

-Chris

SVKarl · 03-12-2007, 07:56 AM

I have my arms around how to adjust the plate angle by re indexing the splines. I began by calculating the angle I needed (same for both sides) and assembled. The right side was over an inch higher than the left. the left was about 3/4 inch lower than I want and the left about a half inch high. To get to the height I am shooting for (24 1/4) I have had to reindex the right upward (clockwise) and the left downward, also clockwise. My question is what is up with the big difference in the relationship of the resulting spring plate angles to one another as I get close to the ride height I want?
Karl

SVKarl · 03-12-2007, 07:59 AM

Shocks off, bottom bar cover bolts out. Also, as an aside, the released trailing arms are almost the same height off the floor, meaning the car is sitting flat left to right on the stands.
Karl

Loaded · 03-12-2007, 08:08 AM

I just did this last night. But I used NEatrix.

As for angle I eyeballed the installation the plates on both side had to be lifted just a hair (heavy hair) on both side to get the lower left bolt in the spring plate cover.

I centered every nut and bolt including ride height adjuster and the set up came out perfect. 25.5 fender lip measurement on both sides.

I maybe be lucky but if everything is equal or very close to equal and all adjuster are don and set for mid adjustment you have to be very close.

Be sure to relax the entire set up remove shocks from trailing arm.

cbeers · 03-12-2007, 08:47 AM

Hey Karl,

Forget about nice shots, let's see what you are seeing.

Can you post us some pics ?

I am struggling to understand what's up.

-Chris

SVKarl · 03-12-2007, 08:55 AM

cbeers. At the moment it is all reassembled and aligned since I was able to get the ride heights within a quarter inch with indexing and then I dialed them in with the adjustment bolts on the plates themselves. I am just wondering why the resulting angles of the plates relative to each other to achieve the equal ride heights from side to side were so different. I will likely disconnect everything this weekend and take some photos. Karl

cbeers · 03-12-2007, 09:01 AM

I think I am getting it now Karl.

When I was done, I set my Tbars to the exact same angles.

Once at the shop though, they adjusted things using the ride height bolt and the front end. A little here, little there and it was good.

That being said, it's not that often that every fender well height comes out exact as well as the corner balance weights. At least what I have seen. Often, the heights will be a little off and you have to adjust the SP to compensate.

When all was said and done, my car was close, but they still moved the driver's side ride height bolt quite a bit. Enough that I could clearly see where the two pices on the SP had moved and revealed the old position.

It might still show up like that. I'll check tonight and snap a shot to show you what I mean. Maybe that is all you are noticing too?

-Chris

ZOA NOM · ZOA NOM's Garage

Are you sure you don't have two different size torsion bars? That would change the droop individually.

SVKarl · 03-12-2007, 11:56 AM

Zoanas, That is what I was wondering, I have pretty good records from the PO, no indication of any work at all on the suspension, plus the rubber bushings looked original and I saw no evidence of any of the fasteners ever being touched. Never the less, seems like the only way to tell would be to pull out the TB and measure them. As I inciated in my original post, if I remember one was painted green on the end and one white, right and left respectively, I think. While I had no reason to think they are different, I also did not set them side by side to compare.
Chris, This is more than tweaking by the adjustment bolts, when completely disconnected and slack, the droop of the left plate is probably four inches below that of the left in order the get equal ride heights from side to side. Sure wierd, huh.
Karl

cbeers · 03-12-2007, 12:08 PM

This is weird.

I don't think that even having two different sized Tbars would matter for initial SP angle/droop as it is set under no load, simply by splines, which are the same no matter what sized mm Tbars. Now, obviously, you'd set up different angles for increased Tbar thickness etc. but we are talking about just initial droop, no load, not attached to the trailing arm.

This is really strange Karl. All I can think of would be that one SP is not fitting well with the SP bearing? Did you check for full range of motion before installing the tbars?

If all else checks out under no load/full droop and you are still seeing something off side to side in the trailing arms I would at least inspect your trailing arm bushings to the tub. Those are the only things I can think of that would affect the way the trailing arm falls if all else is disconnected....

Sorry I can't be of more help on this one.

Here is another "just making sure" idea. Are both SP adjuster bolts set at center? If not, that is an issue that would mess with your set up.

Other than that, at full droop, not connected to the trailing arm, the SP angles should be able to be replicated on both sides.

Keep us posted on this, I am curious now.

-Chris

SVKarl · 03-12-2007, 12:35 PM

Chris, truely a head scratcher. Every way I look at it, it seems that for whatever reason the left tbar is fatigued, assuming someone didn't put in two different bars. The other strange thing is that the car handles just fine. Seems like a problem with the recieving splines internal to the tube would result in inability to "load" the bar or some other handling problem. It will be interesting to see what other thoughts people have, I sure can't come up with anything. Hate to be breaking new ground. Also hate to drop $500 on new bars on top of the 2k it going to be for all the parts to replace the shocks and go through the front end this summer. Stay tuned.
Karl

dfink · 03-12-2007, 01:04 PM

Take into consideration that the front adjustments can effect the rear once placed on the floor. Make sure the front adjusters look close to the same. Do a tripod lift to see if the fronts are about the same when the rear is balanced on the center of the engine.
Make sure the rear swaybar is disconnected from both trailing arms. It is easier if the axles and the shocks are disconnected when doing the adjustments. For certain the shocks bottom bolt must come out when time to line up the trailing arm to the spring plate.
I would then completely start over both sides using the spring rate calculator. Set the angles for the stock torsion rates and the shocks and sways disconnected you should be able to attach the trailing arms without jacking up the springplate. Sounds dangerous to preload the torsions. Also remember that the car may be different heights on each side after the corner balance. Also make sure that the adjustment cams are set in the neutral position so you can adjust both ways for the final corner balance.
Others have much more experience but I have found that when things don't make sense go back to the basics and start from scratch.