Just been to check the old/original rear shock absorbers (Porsche Logo sticker but can't read the Part number) and on reflection these are*Oil filled shocks without pre-load (They stay in place if you move the piston)*and not Gas shocks that have lost their pre-load (which I thought was the case before today).* The new fitted rear shocks (BOGE Part Number 91133305117/1) are defo Gas Pre-loaded !!!

So I guess the exam question is could the fact I have pre-loaded Gas shocks and not Oil shocks (As original) cause L & R ride height differences after Spring Plate angles are set identical.

So this morning I disconnected the shock absorbers both sides and then bounced the car remeasured ride height absolutely no difference ! For information the pre-load in the shocks is not significant and the piston can easily be pushed in with the palm of your hand.

So, either later today or tomorrow I plan on re-setting the Right/lower (7mm) this is the current difference L/R when measured from Floor to center of torsion tube to obtain a 7mm increase I expect this will take 1 or 2 spline increments, if this does not fix it, in order to eliminate the spring plate/outer spline pocket moving*I will fit the original RH spring plate and spline pocket .

I will have then Run*out of ideas.

Q. Is it acceptable to have a different L/R free spring plate angles in order to achieve same LH & RH ride height ? if yes how big can the difference be before you consider you have a problem, it just may be I don't have a problem if the difference can be +/- 1-2 spline increments (1*increment being = inboard 1 anticlockwise and 1 outboard clockwise............).

You should take a look at your left front.

When corner balancing, weight can only be moved diagonally. So the opposite corners have an affect on each other.

To eliminate that variable, try place floor jack centered under the front crossmember in the exact center with some sort of black or half pipe to act as a pivot. Then raise the jack until the front wheels are just off the ground.
Now your rear heights will be more accurate. This will tell you if there really is a torsion bar issue in the right rear.


Also, I have seen a torsion bar start to split down the seem between two splines. It made the car sag in that corner.

Many thanks, tried a bunch of stuff today and came to the same conclusion. .. Something is holding the Rear RH side lower, I'll look at Left front corner tomorrow. I've tried 2 TB no change so don't believe its the TB/s.

To answer your earlier question about the springplate angle:

No, I've never seen the passenger side springplate angle needing to be higher than the driver's side.
Of course, when I'm corner balancing a car I almost always have driver weight in the car. I typically start with the driver's side one degree steeper than the passenger side, and it stays about that same spread by the time I'm finished. The amount of difference is different for the bar stiffness.

There would have to be a lot of twist in the chassis for it to end up with more angle on the passenger's side.

I guess if you were setting it up without driver weight, it could be that way, but I would expect less than half a degree difference.

Any chance the left front torsion adjuster is too high?

What I usually tell people that don't have scales is to set the rears even with the front raised off the ground on the center pivot like I mentioned earlier. Once that's done, drop the nose and settle the car. Then get the fronts even. That gets you in the ballpark.

This must be done on a perfectly flat surface.

Thanks again for your thoughts
Car is UK RHD
Now think front LH adjuster to high, check tomorrow.

Did you replace the rubber spring plate bushings?
If so, i wonder if the bushing could be slipping? Under normal operation, the bushings should not slip either on the shaft of the spring plate or inside the bore of the torsion tube & spring plate cover. They do contribute to the effective spring rate, so if they are slipping it could affect the ride height.

All bushings front & rear and spring plates all new. Don't know how you check them for moving as once on the ground rotational movement at the bushes would be very small

RHD car passenger side is on the Left, Driver side Right so looks like I could expect slight increase in spring plate angle on RH/Drivers side.

Re baseline close of play yesterday:

After realising my rear TB to floor measurement differences were incorrect i.e. yesterday I actually started with a 7mm difference not 13mm (I have corrected Post). After yesterdays efforts playing with RH spline adjustments and also recognising that there is a couple of mm relative difference in wheel arch heights i.e. the RH side is lower than the LH side, I am now only using the bottom edge of TB to Floor as relative ride height, the L/R difference now is about 2mm which today I hope can be further reduced by a) Recognising my floor is not flat flat, b) Maybe Wiggle room on front Left ride height and c) My spring plate adjusters are in the mid position so some scope here.

So today a slight lowering (1/2 turn) of the front left adjuster all 4 corners tortion bar pockets to floor perfect just where I want everything, go for 40 mile drive and all 4 corners 6mm lower ! Normal ?

Haha, OK, it's right hand drive. Didn't see that in your earlier posts.

Glad the LF adjustment brought it in. Yes, it's totally normal for it to settle a bit, after a drive.

Torsion bars don't lose rate. They can take a set - a permanent twist, if you will - over time or from overloading. When the splines are reset they behave as before. Or they break. Crack at a spline is a new one on me, but that would follow the paradigm. So no slow settling. But a, say, 200 pounds per inch torsion bar, like a coil spring of the same specs (yes, T bars aren't speced in lbs/in, but there is an equivalence) will always have that rate until it breaks.

But you seem to have resolved the issues.

Torsion bars can get harder as you age.

Also, they can vary either up or down over time. depending on gfs or wives.

All sorted and all within a couple of mm, I think the main things I was doing wrong:

At the start not making big enough increments on TB.

Not keeping car config constant i.e. Fuel, spare wheel, tools, jack.....

Not waiting long enough for adjustments to settle, especially the tire preload, as I was bouncing the car but this did not remove the tire preload, going for a drive was best.

Initially I was using the floor to wheel arch as a ref, this gave me hand built car errors, so used the TB pockets to floor much more reliable.

For some reason I had it in my mind that the spring plate should not go beyond 33°/ past the cover plate spring stop, then I found the ER spring plate angle calculator which gave me 37.4° for 23mm TBs !

A math errors in the middle of the whole process did not help either.

Will now drive for a few days to make sure everything is stable and then get the 4 wheel alignment done.

Thanks to all for your support.

my car has sagged about 1 in the rear since I installed the new torsion bars in 2014