Front Suspension Torsion Bar Re-Install Question

[CobraR1339]

The car has been apart for a long time. I just got all the parts back from powder coater. I did not take it apart.

Is there a Left and Right for the front torsion bars ( stock 69 911) ? I do not see any marks on them. Does it matter?

One of the Rears has an L stamped in one of them, I assume that would go on the drivers side ?.

When re-installing the front suspension any pointers to make it easier ? , everything is off right now, rack , etc. Pelican rubber installed.

THanks

[Catorce]

I think on the stock bar, unless it is marked, there is no difference. There definitely is a difference on aftermarket bars and yes, L is the driver side.

Clean the ends off real good and look for markings. Hand thread the mounting screws for the LCA brackets and the crossmember; don't torque anything down until it is all assembled correctly.

make sure all brake connections to the MC are installed and ready to go before mounting the cross member.

Make sure and grease the ends of the torsion bars to prevent corrosion and make them easier to remove in the future. The way it goes back together is pretty straightforward.

[garment]

If you have elephant bars, can you take a pic of the ends and post them? I'd like to see the markings, thanks!

Originally Posted by CobraR1339

The car has been apart for a long time. I just got all the parts back from powder coater. I did not take it apart.

Is there a Left and Right for the front torsion bars ( stock 69 911) ? I do not see any marks on them. Does it matter?

One of the Rears has an L stamped in one of them, I assume that would go on the drivers side ?.

When re-installing the front suspension any pointers to make it easier ? , everything is off right now, rack , etc. Pelican rubber installed.

THanks

[chris_seven]

All standard torsion bars supplied by Porsche should be marked Left and Right and it is prudent to install them in the correct orientation.

If the bars are unstamped they are likely to be aftermarket and in general if they are unmarked it doesn't really matter.

The reason for the marking is simple -


It is custom and practice when making new springs that they are loaded to virtually coil bound in the case of coil springs and to just past their yield point in the case of leaf springs and torsion bars.

This process is known as 'scragging' and is generally part of a final test procedure and in my experience all springs produced by car makers are 100% tested. this procedure is some times called presetting but always involves some plastic deformation.

scragging or presetting - IEC

When a torsion bar is scragged it is twisted to just beyond it's yield point which effectively increases the strength of the material but does not change the torsion bars spring rate spring rate and this creates an unusual condition.

If the torsion bar is then used in the opposite torque helix the yield strength of the material reduces slightly and this is known as a Bauschinger Effect.

In extreme circumstances this could affect the fatigue life of a torsion bar but in practice I think that the effect would be insignificant and I wouldn't worry.

Some after market torsion bar manufacturers claim to preload torsion bars to 90% of their yield strength and from a metallurgical perspective this may help to eliminate any initial set as it it will help to transform any residual austenite but there would be no need to mark the springs left and right as loading to less than the yield point will not create a Bauschinger Effect.

If you can't tell which bar is which I would not be greatly concerned.

[garment]

Thanks for the info/reassurance. I was NOT interested in tearing apart the a-arms I just attached to the car!

Originally Posted by chris_seven

All standard torsion bars supplied by Porsche should be marked Left and Right and it is prudent to install them in the correct orientation.

If the bars are unstamped they are likely to be aftermarket and in general if they are unmarked it doesn't really matter.

The reason for the marking is simple -


It is custom and practice when making new springs that they are loaded to virtually coil bound in the case of coil springs and to just past their yield point in the case of leaf springs and torsion bars.

This process is known as 'scragging' and is generally part of a final test procedure and in my experience all springs produced by car makers are 100% tested. this procedure is some times called presetting but always involves some plastic deformation.

scragging or presetting - IEC

When a torsion bar is scragged it is twisted to just beyond it's yield point which effectively increases the strength of the material but does not change the torsion bars spring rate spring rate and this creates an unusual condition.

If the torsion bar is then used in the opposite torque helix the yield strength of the material reduces slightly and this is known as a Bauschinger Effect.

In extreme circumstances this could affect the fatigue life of a torsion bar but in practice I think that the effect would be insignificant and I wouldn't worry.

Some after market torsion bar manufacturers claim to preload torsion bars to 90% of their yield strength and from a metallurgical perspective this may help to eliminate any initial set as it it will help to transform any residual austenite but there would be no need to mark the springs left and right as loading to less than the yield point will not create a Bauschinger Effect.

If you can't tell which bar is which I would not be greatly concerned.

[CobraR1339]

Thanks for the re-assurance on the front bars position.

Also thanks for the tip on the lines for the master cylinder. I just trying got make the car a roller and get it off the body dolly right now while still at the paint shop.

The old metal lines are there, but was going to buy new ones. the plastic lines are in. I guess I maybe be pulling it one more time, if that tight. But the painter wants me to pick it up.

[CobraR1339]

Originally Posted by garment

If you have elephant bars, can you take a pic of the ends and post them? I'd like to see the markings, thanks!

The Torsion bars I believe are original to the car. At least stock sizes. Solid bars, painted black with a white paint stripe in the middle of the rear bars.

When I cleaned the bar used a stainless brush on the splines, I did find a R stamped into one front bar and possibly an L , but very faint. The rears had no marking for right, but one had a large L stamped in it.

Maybe this will help some one.. The rear swing arms were really crusty inside. I filled the tubes with PB blaster and used and engine brush to scrub after an overnight soaking. Stuck the T bars in and moved them in and out until they were smooth in any orientation. Rinsed them out with brake clean. Added some redline WB grease I had laying around. Now they are as smooth as can be.

Now to come up with a way to clean out the center tube on the car. Also very crusty looking. The Ford engine brushes will reach, but think they may be are too thin and flexible.

Really want all this stuff fitting smoothly, as I have no reference marks for the rear swing arms to get the ride height correct. I hear it will be a lot of trail and error.

[garment]

I heard back from Chuck at Elephant. The plated/plugged bars at least are not side-specific - at delivery. Once you install them, you should maintain the side of install if it is the case that you remove them.

You can't believe what a comfort it was to hear this!

Originally Posted by chris_seven

All standard torsion bars supplied by Porsche should be marked Left and Right and it is prudent to install them in the correct orientation.

If the bars are unstamped they are likely to be aftermarket and in general if they are unmarked it doesn't really matter.

The reason for the marking is simple -


It is custom and practice when making new springs that they are loaded to virtually coil bound in the case of coil springs and to just past their yield point in the case of leaf springs and torsion bars.

This process is known as 'scragging' and is generally part of a final test procedure and in my experience all springs produced by car makers are 100% tested. this procedure is some times called presetting but always involves some plastic deformation.

scragging or presetting - IEC

When a torsion bar is scragged it is twisted to just beyond it's yield point which effectively increases the strength of the material but does not change the torsion bars spring rate spring rate and this creates an unusual condition.

If the torsion bar is then used in the opposite torque helix the yield strength of the material reduces slightly and this is known as a Bauschinger Effect.

In extreme circumstances this could affect the fatigue life of a torsion bar but in practice I think that the effect would be insignificant and I wouldn't worry.

Some after market torsion bar manufacturers claim to preload torsion bars to 90% of their yield strength and from a metallurgical perspective this may help to eliminate any initial set as it it will help to transform any residual austenite but there would be no need to mark the springs left and right as loading to less than the yield point will not create a Bauschinger Effect.

If you can't tell which bar is which I would not be greatly concerned.