Re-installing Torsion Bars - stock ride height

[944m3]

Finally bit the bullet and decided to refresh my rear suspension. I don’t have the torsion carrier off yet but almost there. Probably have it done over the weekend. I’m replacing all rubber with Elephant Racing sport line. I’m purchasing new spring plates with bushings already installed, I don’t want to wrestle with removing the old rubber.

I’ve watched videos and read-up on how to reinstall the torsion bar but it’s not clicking in my head. I don’t want to change my ride height, does that mean I just need to reinstall the spring plates at the same angle as they were? Are there marks I can follow? Maybe I just need to see it myself but I’m not understanding how turning the torsion inside the carrier changes ride the height. (But again, I want to keep stock height). My brain is lacking the power to light that bulb!

Also, is it worth buying the adjustable spring plates to avoid having to deal with indexing the bars?

I really hope all this work is worth it because it’s a pain. Hoping the new rubber all around gives me a quieter smoother ride.

[cda951]

The torsion bars have a different spline count for the inner and outer ends ----40 splines for the inner end, 44 or the outer end. The basic ride height setting is determined by measuring the angle of the relaxed angle of the spring plate with the control arm/shock disconnected (a smartphone angle finder that measures in minutes should be sufficient).

According to the Porsche 924 factory service manual, if one were to rotate the torsion bar by one spline on the inner/body end, the angle of the spring plate changes by 9 degrees. If one rotates the spring plate by 1 spline on the outer end of the torsion bar, the angle changes by 8 degrees, 10 minutes (60 minutes per degree). So the the result of rotating the inner end of the left side torsion bar counter clockwise by one spline, and then the spring plate clockwise by one spline would have a net result of 50 minutes less angle at the spring plate, which would lower the ride height.

With the car on jack stands, you should note the angle of the relaxed spring plates before loosening/removing the torsion bar tube. If you are lucky enough to get the spring plate off the torsion bar and the inner end of the bar stays engaged in the tube on the inner end, it should be easy to re-establish your basic spring plate angle and maintain your set ride height.

The 944 has an eccentric ride height adjustment for fine-tuning, which has maybe 3/4" of adjustment range. This is more useful for corner-balancing purposes.

Be careful and have a helper present if possible, the spring plates are under tension from the torsion bars, and can seriously injure someone if the spring plate slips off the floor jack while attempting to relieve tension.

Also, the torsion bars are marked L and R on the outer end caps for left and right---each is tempered in the direction it is designed to twist. I once had a customer 968 that was sagging in the rear, turns out the torsion bars were swapped left to right.

Good luck and let us know if you need help. I have a hand-written cheat sheet somewhere with the trigonometry formula for calculating the exact ride height of a 944 with different torsion bar sizes and angles, would probably take a while for me to dig that up . . . . .

[944m3]

Thanks for the detailed response. I think that makes sense.

You mentioned measuring the angle of the relaxed spring plate, which I assume with the wheel off and shock which I already removed. Would I be able to measure the angle with the carrier assembly off the car and spring plates still attached?

Thanks for the tip, will get my son to help. I plan to have the carrier off tomorrow.

When I re-install, am turning/twisting/rotating the spring plate and cap to the correct angle to get tension in the bar before bolting on? This part is what I’m having trouble picturing in my mind.

[cda951]

Thanks for the detailed response. I think that makes sense.

You mentioned measuring the angle of the relaxed spring plate, which I assume with the wheel off and shock which I already removed. Would I be able to measure the angle with the carrier assembly off the car and spring plates still attached?

Thanks for the tip, will get my son to help. I plan to have the carrier off tomorrow.

When I re-install, am turning/twisting/rotating the spring plate and cap to the correct angle to get tension in the bar before bolting on? This part is what I’m having trouble picturing in my mind.

By "relaxed," I mean with no tension on the torsion bar. Spring plate is bolted to the torsion tube, but nothing else is bolted to the spring plate (trailing arm and shock are not attached to the spring plate). Lower spring plate cap to torsion tube bolt is removed to allow the spring plate to fully rotate downward to the relaxed position.

Once your angle is set, you will need to use a floor jack under the trailing edge of the spring plate, which twists the torsion bar and allows the spring plate and trailing arm to be lined up so the hardware can be installed. The opposite is needed during disassembly, need to maintain tension on the spring plate to allow the hardware to be removed, then the tension is slowly released and the spring plate is allowed to rest in the "relaxed" position of the torsion bar. You *might* be able to attach the trailing arm to the spring plate before attaching the lower end of the shock, which would allow you to jack up the spring plate and trailing arm together to line up the lower shock mounting bolt, which would be easier.

See screen shot from the factory 924 manual (later 944 parts look a bit different, but the concept is the same), both pics on the right show a relaxed spring plate, the angle should be measured at this point to ensure that the ride height is the same after reassembly.

[944m3]

I think the light bulb is starting to flicker!

Thanks again.

[944m3]

At this point is where I take the angle measurement?

[944m3]

Also, couldn’t I take the angle measurement with the entire carrier off? Before I remove the spring plates.

Any point in saving the anti-lock brake wiring? I’m assuming that is what the wiring on the upper right of the picture.

[944m3]

Actually, the spring plate bracket is keeping the spring plate from fully extending or relaxing, no? See picture.

[cda951]

Actually, the spring plate bracket is keeping the spring plate from fully extending or relaxing, no? See picture.

Yes, it might be, hard to tell from the picture.

I also realize that posting pics of the 924 manual might have caused confusion, but the reason I posted the 924 manual and not the 944 version is Porsche usually explains a concept only once, when a model is first introduced (such as how the torsion bar splines work). After that, they assume the technician is forever imbued with said knowledge and subsequent manuals explain only updates and differences between the 924 and 944. One of which is the 924 has a welded-in torsion bar tube, 944 has a removable bolt-in tube, hence the difference in torsion bar end caps.

You could measure the spring plate angle with the torsion tube removed, but that makes it more difficult to ensure the base angle of the torsion tube is consistent while measuring spring plate angle. If it is securely bolted to the chassis while on jack stands, the basic angle of the torsion tube is fixed. Your call, though.

[944m3]

Welp, not sure if I’m happy or disappointed.

Got the carrier off the car and removed the spring plate on one side. To my surprise it came off easily. Looking at the bushing I was again surprised by the appearance, it looks good. I’m able to dig my fingernail into the rubber. I tapped it with my hammer and it responded like good rubber, if that makes sense. In other words, they seem fine. The trailing arm bushings also seem fine, they are playable. (I used a long screw driver to “wiggle” the bushing and it felt “bouncy”).

I can’t tell if they are original or not. I could not see any obvious evidence that anyone had taking any of the bolts off. As far as I can tell it’s the OEM shock too. The car has over 100k miles.

Question, is this normal or should the rubber be hard as a rock? At this point I’m not sure if I should just put everything back together or proceed with swapping bushings. I could use the money for other things for sure.

Thoughts?