Ride height - Adjustable spring plate "indexing"

[Wyvern]

Hi Folks.

My 75 is now On the Road after lots of interior work and a 2 month CIS "journey"

I do have adjustable spring plates on the rear.
Want to drop the rear a bit more but one adjuster is at max drop and the other has a way to go.

Is this a case where I need to "re index" the Rear Bar in the spring plate?

Big PITA or ... a straight forward task.

[carrera turbo]

i would say you need to move a spline. but check the front and see if you have the same thing one tighter than the other maybe a weak t-bar. or front is way out of adjustment

cheers ed

[jluetjen]

It's a big PITA.

[Wyvern]

Left / right front and left / right rear ride height is spot on side to side ...
It is the Rake that I don't care for...
All the suspension "seems to be OK .. nice ride and no pull ect.

I will search and see if PITA is of a level that will make me live with this.

Even if the ride height was where I want it ... just knowing this bugs me.

[don gilbert]

indexing the spline is not hard, but you can lose your rear alignment

[rnln]

wyvern,
I am sorry, I have no answer for you on this but your car look very nice. Do you have more pictures?

[Wyvern]

from what I can tell I can index the outer plate and leave the torsion bar inner splines alone. If I mark where it is now with a paint mark or scratch on torsion bar end and plate ...Just 1 spline is all I would need .

Thanks for the complement.
A lot of clean up and elbow grease.

Desperate to refinish the BBS wheels, will blast the outer rim and do black center.






http://c3.ac-images.myspacecdn.com/images02/79/l_a60a288d2dbe4227b027c3c2132b363e.jpg

[jluetjen]

Actually -- One spline is a lot more then you need. The trick is that there is a different number of splines on the inside and the outside of the T-Bar. I don't remember off-hand what it is for your car, but on my '69 there are 40 splines on the inside of the T-bar and 44 splines where the spring plate mates to the T-bar. Moving the T-Bar one tooth results in a change of 360/40=9 degrees. Moving the spring plate by 1 tooth results in a change of 360/44= ~8.2 degrees. If you move the T-Bar down by one and the spring plate up by one you'll move the spring plate down by 9-8.2=.8 degrees. If your car is a '75, I suspect that it's the same. I believe that the Turbos are different.

My own experience is that this is the easy part. The PITA parts fall into two categories...
1) Removing the spring plate for the first time. Chances are the rubber bushing that supports the outer end of the T-Bar has stuck itself pretty well to the chassis and the spring plate. This is especially true if it's been there a long time. When I did this with my car I spent quite some time cursing and swearing over that because it's not that easy to find a place to pivot a lever (aka a pry bar) to pull the plate out. After doing this, I chose to replace my rubber bushings with Elephant Racing's Poly-Bronze bushings which pop in and out by just pulling with your fingers.

2) The spring plates are mounted essentially pre-tensioned. By this I mean that at the correct setting, you will need to get a jack under the spring plate and push it up in order to get it to mate with the trailing arm. Needless to say, this also requires a degree of the "king's English" as you try to support the trailing arm (and brake assembly) in such a way that the holes line up with the spring plate and you can get the bolts and adjusters in. Part of this is due to the fact that the trailing arm moves in an arc centered on it's pivot near the center of the car, while the spring plate essentially moves vertically on an arc centered on the T-Bar. At the lowest extreme of these two arcs (where you'll be when you start putting it together) the trailing arm has moved away from the spring plate by about an inch or so.

Anyhow, when I'm putting it together I usually try to increment it. By this I mean that usually the first thing that I can get in is the toe-adjusters, and then the top bolt with no washers. I tighten this up (but not all the way) which usually will get me to a point where I can put the camber adjuster in. This piece is always tight, and so a little WD40 or Silicon spray helps it to not bind. I'll then tighten that up and adjust the toe and camber adjusters to pull the trailing arm to the point where I can get the lower bolt in -- but usually not the washers. I'll then put the washers on the upper bold and the adjusters and tighten them up a bit and then go back and put the washers on the lower bolt.

Then you need to go and corner-weight and align the car again.

That's the way that I've been doing it. If anyone's got a better strategy -- I'd use it.

[Kemo]

those arent stock spring plates are they? they look alot like the sway-away. If thats the case, then I would hope that its not super stuck in there like a 35yr old bushing might be. When I put my sway-away adjustables in, I tried to follow their rules for presetting the height based on angle to the horizontal based on torsion bar and what not. I wasnt even close. my car was so low to the ground the wheels were touching (resting) on the inner wheel arches. all I did was undo the 4 bolts pull out the outter part only and moved it a tooth or two towards the ground till I got it close. Then I did the fine adjustment with the screw. I had to do it a couple of times to get it close. But like you, my adjuster screws are not the same depth, from side A compared to side B. After reading John's explanation above, it makes more sense now and I could probably get it a bit closer. Unfortuantely, my car is getting aligned right now and ill probably not touch it until I make some changes to the suspension.

[Kemo]

oh...so for you...i guess you need to go towards the ceiling with the adjustment on the side that is not able to adjust any lower.

[911st]

Before you take it apart you might want to do the "tripod method" to check the balance of your car. This is basically taking the wheels off on one side at a time, lower the car to stock height, and check the measurements from the ground to the torsion bar centers. This will tell you if the car is balanced reasonable well. Just measuring to the fender w the car on the ground is not going to tell you this.

With the adjustable rear arms, you should have plastic bushings. If you mark your alignment concentric you should be able to re index the one arm and put things back where they belong and not disturb alignment to a significant deg. However, lowering the car by its self will effect the alignment so you may want to have it done.

Having the plastic bushings and the type of adjuster you have will make it a lot easer to reset the one side. If you mark your alignment concentric and take a measurement of the arm angle before you re index it it should not be a tough job except for things like stuck bolts and such. Get some bushing grease and re lube the bushing.

Here is some info on reseting the arm: http://www.pelicanparts.com/techarticles/911_torsion_bars/911_torsion_bars.htm

[BK911]

It isn't that bad if all goes well, but it never does! So it does turn into a big PITA. Take this opportunity to replace the spring plate bushings if needed.

This is how I do it:
Determine how much you want to drop the car. For this example say 1".
Put the car on jack stands.
Take off the wheels.
Disconnect the trailing arm from the spring plate.
Measure the distance from the ground to the end of the spring plate.
Set the adjustment on the spring plate to about center.
If you want to drop the rear 1", you need to raise the end of the spring plate about 2/3" above the original dimension.
Keep re-indexing until you get the measurement you want.

That should get you VERY close, def enough to use the final adjuster.

[Rodsrsr]

If you pull the spring plate off and move it one notch, than pull out the torsion bar slightly and move it two clicks in the opposite direction, you will get the minimum adjustment (about 1/4") You will need to have a degreed dial indicator to do this properly. Scratching a line on the frame to mark position of the plate will simply not work. If you have never done this before get ready for an all day job. BTW, your car has a pretty good stance as is.

[jluetjen]

Oh yeah! BK reminded me of another "trick".

1) Before installing the spring-plate, I move the adjuster all the way to the top (as if to lower the car). This will relieve some of the pre-load and make attaching the spring-plate to the trailing arm easier.

2) After everything is installed, I move the spring plate to the other extreme (the bottom) since it's easier to crank the car down to the ideal rather then up.

[Wyvern]

Wow ...
thanks to all.

I will look into replacing the bushings ... or at least have lube ready.
The aftermarket adjustable spring plates are a saving grace ...as the adjustment that they have will help get the ride height where I want it even if "off" on indexing .. Where I am now proves that.
The tripod method will be a test that I will do first (maybe TONIGHT, better to do that than to go out and play CINCO)

good info . the job doesn't intimidate me . but understand where the PITA can raise it head.

[911pcars]

"Before you take it apart you might want to do the "tripod method" to check the balance of your car. This is basically taking the wheels off on one side at a time, lower the car to stock height, and check the measurements from the ground to the torsion bar centers. This will tell you if the car is balanced reasonable well. Just measuring to the fender w the car on the ground is not going to tell you this."

The "tripod method" presumes lifting one end of the vehicle from a side-to-side mid-point location to isolate the 2 front corner height settings from the 2 rear corner settings.

IOW, this is a comparison between the F/R ends, not a comparison between the L/R, sides.

Not sure how much height change is represented by one outer spline change (per John's report of ~8.2 degrees). However, one spline change might bring the SAW spring plate into its normal range of adjustment.

Here's a suggestion:
Lift and support both sides of the rear an equal amount.
Unbolt both spring plates from their control arms, thenn remove both torsion bar covers. Measure and record the free hanging angle of each spring plate. If both torsion bars have equivalent wear, both spring plates should hang at the same angle. Confirm accuracy by measuring and recording the vehicle angle at each L/R door sill plate.

Pull the desired spring plate free from its torsion bar and adjust the inner and/or outer spline engagement accordingly. To separate the torsion bar from the spring plate and/or keep the inner TB splines engaged, create outward force on the spring plate while motivating the TB to move using a large drift and hammer through the open end of the spring plate splined tube.

Sherwood

[jluetjen]

create outward force on the spring plate

Easier said then done!

[911pcars]

Originally Posted by jluetjen

Easier said then done!

Easier done with 2 sets of hands and two large pry bars.

Sherwood

[911st]

It is hard to remove the arms w stock rubber bushings. I bet along with those adjustable arms came hard bushings. It should be relatively easy (still must pry) to remove the swing arm unless the torsion bar has become rusted stuck.

8.2 deg is about 1.3" at the wheel.

The try-pod measures the ride height of the two corners supported by wheels. By doing each side separately, you can compair the height measurement (at the bar end) to the other side of the car.

If the right front is higher by .5" and the left rear is higher by .5" the car may sit level when on all four wheels but will have pre load built into the two opposite corners that cancel each other out and let the car sit flat. It is the best way to check ballance with out corner ballanceing and I belive though up by Chuck of ER.

If the one side has adjustment sufficient to lower the car to its desired height, there is no reason to take the other apart.

I would suspect that if this car has adjustable rear spring plates there is a good change it has stiffer torsion bars.

I referenced the tech article above that describes how to reset your arms. I thought that would cover what was needed. However, as may be noted above, the swing arm may be under tension. You can either support the tip of the arm carefully w a bottle jack before the attachment bolts are removed or disconnect the shock and lower and support the arm (correct way).

With the aftermarket adjustable arms it might be the car has stiffer torsion bars. If so, there is a chance that there will be sufficient travel so that the spring my not be under tension. Us caution.

Something else to consider. If the car dose not have any negative rear camber, adding it will lower the back of the car. On a stock SC each deg of neg camber lowers the rear by 7-9mm. With turbo width wheels it may be more than that. Each deg of added neg camber should lower the back by .35" or so I suspect.

Good luck.