Rear springplate installation ?s

[michael lang]

Since I haven't been able to do much in the way of winter projects and now that I'm learning to walk again I can't wait to get started. Althought the parts have been coming there's a couple of things on my list that I'm not sure of so I thought I would turn here for guidance.

Along with the gama of normal pre-season maintenance items to get ready for track season. 1. to replace the rear springplates. 2. to replace the rear monoballs.

Questions:
When replacing the spring plates will I need to worry about the indexing of the rear torsion bars? After reviewing the Bentley manual it appears as though it is slightly more than bolt off, bolt on. Would someone comment on this please?

Can the trailing arm bushings be removed from the arm while it is still bolted on the car or will the trailing arms have to be off first in order to remove the bushings and press in the monoballs?

I do not have a lift at home so I will be working with jackstands and crawling around on the floor and my skills are probably intermediate level and I am fully aware that an alignment and corner balance will need to follow. Does this sound feasible?

[BK911]

Scribe a line marking the angle of the spring plate on the tub. When reinstalling use the line as a reference.

If you are replacing the spring plates, you need to unbolt the trailing arm from the spring plate. If you are replacing the trailing arm bushing, you need to unbolt the trailing arm from the chassis. So I am confused by your question.

[michael lang]

Okay, I knew about scribing a line in the trailing arm and the importance of it but what I really wanted to know is do I need to worry about reindexing the torsion bar to make sure I get the angle or degree of the torsion bar correct? Is the spring plate itself a bolt off and bolt back on, or do I need to check and record angles for ride height first? As far as the trailing arm bushings are concerned, would it be easier in the long run to remove the trailing arm, remove the old bushings, press in the new monoballs, and reinstall the trailing arm? Or should I just let it hang from the front after unbolting it from the chassis, replace as needed?

[boyt911sc]

Mike,

Are you replacing your current spring plates with another set? If NO, you could leave them in place and just remove the trailing arms for the monoball installation. Unless you are re-indexing the torsion bars which you never mentioned.

If you are putting a replacement spring plates, it would be almost impossible to remove and install the spring plates back without disturbing the original setting. You could be lucky but you can not depend on luck all the time.

What you are planning to do is a common maintenance work done everyday by DIY'ers and should have plenty of advise and help available to you from members of this forum. An angle finder (electronic) would be very helpful in doing this job.

Tony

[BK911]

I am still a little confused on what you are asking.

You are replacing the spring plates?
You are replacing the trailing arm bushings?

The trailing arm is connected at 3 points. Shock, chassis, and spring plate. If you are replacing the spring plate, that connection is gone. If replacing the chassis bushing, that connection is gone. Why leave it bolted to the shock? Take out the one bolt and replace the bushings on a bench.

If you put the spring plate back on so it aligns with the scribed mark, you will not have to reindex the torsion bars. That is the point of the scribed line. If you remove it at X angle, and install at the same X angle, your ride height will be the same.

[BK911]

Oops, forgot about the brakes. Emergency brake cable and brake lines are attached too.

[boyt911sc]

Originally Posted by BK911

Oops, forgot about the brakes. Emergency brake cable and brake lines are attached too.

BK911,

The CV's have to be disconnected to get the trailing arms off the car for the monoball install.

Tony

[michael lang]

BK and Tony, sorry I wasn't very clear. I will be replacing the stock spring plates and trailing arm bushings with adjustable spring plates and weathersealed monoballs. I'm fully aware of the mounting points of the trailing arm and also the reasoning behind scribing the trailing arm with stock plate for guidance on the replacement part. I was asking because I was hopeful that someone on this forum had already performed these upgrades and they would give some input as to what would be the best way to approach this. So let me try it this way.
When the stock spring plates come off and adjustable spring plates are installed, will I need to re-index the torsion bar to match my current ride height?
Would it be easier to remove the current trailing arm bushings and install the monoballs with the trailing arm in or out of the vehicle?

[BK911]

Originally Posted by boyt911sc

BK911,

The CV's have to be disconnected to get the trailing arms off the car for the monoball install.

Tony

DOH! My car has been a roller far too long.

So the 3 points of attachment are:
chassis
spring plate
shock
ebrake
brake
cv


Michael, is this for your '89 Carrera? You should already have adjustable spring plates.

[michael lang]

Originally Posted by BK911

Michael, is this for your '89 Carrera? You should already have adjustable spring plates.

Yes it is and no it doesn't.

[boyt911sc]

Originally Posted by michael lang

Yes it is and no it doesn't.

Michael,

Without seeing your '89 car, I doubt if anyone would install a non-adjustable spring plate when adjustable SP are stock item. I could be wrong but I've never seen a late Carrera 3.2 with the older SP plus the sway bar mounting is totally different.

Take a picture of the spring plate and we could tell you if it is adjustable or not. I bet you already have the adjustable ones!!!!

Tony

[rusnak]

Ah crap. Posting on my phone lost a long and pretty good answet.

In short: maybe yes maybe no depending on where the new springplates end up in the spline lottery.

Inner and outer splines counter rotaed to give 1.5 degrees of rotation.

Re-use old springplates, answer is "no". And you should not worry about pulling the t-bars from thr torsion tube since you are doing the whole removal anyway except for that one last item.

[Wil Ferch]

FWIW......you "index" the TB by looking at the free-hanging angle of the spring plate. It needs to be at a certain "droop" for a given weight of car, a given torsion bar diameter, and such.

It stands to reason that if you take things apart...and you put them back together again, that you need to re-establish the same "droop" if nothing else has changed ( same car, same weight, same torsion bar diameter ).

So "yes"......you need to re-index the torsion bars as you put things together. Don't forget, when measuring "droop", you need to remove the lower/rearmost spring plate cover bolt, or the suspension will simply "rest" on this bolt and you'll never know the true free-hanging "droop".

Tom Fitzpatrick ( "Widebody911") and I collaborated many years ago and came up with a spring plate angle calculator ( do a search on key words spring plate angle calculator), .....but this helps guys if-->

1.) you keep the hardware ( torsion bar diameter) the same and want to "target" another ride height, typically "lower"....or

2.) you change something, like add fatter (stiffer) torsion bars. You need a way to get back to (say) the same ride height when you installed fatter bars, and you have nothing to reference yourself back to. Scribe marks won't work here as a different angle will be used.

Yes....you probably have adjustable spring plates....but they do NOT adjust like the Weltmeister brand, so maybe you are being confused by that.

[Flieger]

Factory type are better. The screw type ones can flex too much, come off the perch and collapse on the track.

[michael lang]

Originally Posted by Wil Ferch

Tom Fitzpatrick ( "Widebody911") and I collaborated many years ago and came up with a spring plate angle calculator ( do a search on key words spring plate angle calculator), .....but this helps guys if-->


2.) you change something, like add fatter (stiffer) torsion bars. You need a way to get back to (say) the same ride height when you installed fatter bars, and you have nothing to reference yourself back to. Scribe marks won't work here as a different angle will be used.

Yes....you probably have adjustable spring plates....but they do NOT adjust like the Weltmeister brand, so maybe you are being confused by that.

This is what I was hoping for. I do have fatter t-bars and my car's ride height is conciderably lower than stock set-up. I will do the search on the spring plate angle calculator. I believe you are correct, I probably do have adjustable spring plate (stock) already and since the ones that I'm going to install are Sway-A-Way and have the adjustment point in the middle of the plate I probably have it confused.
The reason for this upgrade and some others that I'm doing is because this past season my car did not feel very balanced while on track and my tires wore very unevenly on the right side of the car vs. the left side but the car did not pull. When talking with the tech that performed the alignment after I installed the t-bars last year he told me that the alignment was at max adjustment but overall needed more neg. camber.

[Wil Ferch]

Maybe you're still missing a point ( or maybe I am)--->

If you have fatter torsion bars *already*....and simply want to get back to where you were previously prior to tear down/reinstall.....then you *do* use the scribe mark method. My point made about "fatter" torsion bars means if you took out thinner bars and as part of the reinstall....you are replacing with fatter bars. Then you use the spring plate angle calculator.

The "issues" you have might also be the degree of corner balance you have....and not alignment.

[llangston1]

What car weight do you use for the online spring plate angle calculator? Do you use the "empty" or the "max allowable" weights that are listed in the owners manual? I have a stock 87 carrera and am upgrading to 28mm rear bars so i want to get the angle right. The spring plates with the original bars were set at ~31 deg.

[70S Targa Guy]

I will let Wil answer that. However, what I will tell you is I used Wil's wonderful Spring Plate Angle Calculator when I did my very first torsion bars, adjustable spring plates, bushings, etc. upgrade. I used the actual weight of my car, (maybe that is the empty weight you are referring to...I actually had my car weighed on a big scale) added my body weight and added about 50 pounds for a half tank of gas. That is the total sum of weight I inputed into the calculator to get my spring plate angle and using that angle I achieved EXACT Euro height on my very first attempt. That's what worked for me but as usual YMMV. Thank you Wil.

[Pazuzu]

Try 2700 pounds. I found that mixing up that value by 200 pounds each way gave a very limited range of results (like, 30-33 degrees). I also played with numbers until I found a weight that gave me my current height with my current bars, and found that weight to be well within my range I tried.

What it came down to was, you don't have to be that exact. 2700 should be fine for a stock Carrera.

[Flieger]

You want the actual weight of the car as it sits with you in it.