Will used torsion bars settle after indexing?

[Mike_72]

I just finished re indexing my torsion bars by about 1.5 degrees to lower the car a little and also installed new Neatrix spring plate bushings. Now the car seems to still be sitting at the same height as it was prior to making the adjustments. Can I expect the car to settle over time even though I used the same torsion bars, or will I need to pull it apart again and re adjust?

[patz]

Drive it.

[1QuickS]

Springs will creep over a LONG time, not a short term issue. Hopefully you kept the right side t-bar on the right side, etc.

Possibly the rubber bushings allowed a local sag which allowed car to sit lower and the new, harder bushings removed that compliance.

Drive the car a little & check. It would be very good to corner balance once ride height has been finalized.

[Driven97]

Did you drive / bounce the car? Bushings may be a little twisted from being jacked up and a little drive might get them to settle.

[Mike_72]

Unfortunately the car is not drivable at this time, I did bounce the car and it stayed pretty much the same.

[Flieger]

Springs no. Bushings yes, after a long time. They contribute to spring rate as well if you use rubber ones so new ones of a different brand could cause the extra height.

[Mike_72]

Another question I had was regarding how far into the spring plate do the torsion bars normally sit?? Mine are just about touching the cap on the outside of the spring plate. I want to be sure they are sitting deep enough in the splines on the inboard side.

[brianlay]

Something doesn't quite add up here.

You're saying you changed the spring plate angle by 1.5 deg and you saw no difference in ride height? Doesn't seem likely.

A 1.5 deg change should've given you about 12.5 mm (.5 in) difference in ride height. What amount of lowering were you aiming for? What model/year is this car? I'm guessing you really didn't change anything at all. I think you're going to end up re-doing it. Were you using some sort of measuring device to confirm the before and after angles?

As far as re-assembling, I don't think you can really mess that up.....if you were able to bolt on the retaining plate everything should be fine.

[Mike_72]

I used an analog inclinometer to measure before 35 degrees L/H and 34 degrees R/H and subtracted 1.5 degrees from those number when I reassembled. One person has mentioned that the new bushings could contribute to the increases height? What about the toe and camber settings? Could they have an effect on the ride height? I am also very puzzled by the fact that the right hand side seems to sit slightly higher even though the spring plate is adjusted a degree lower. Any explanation for that?

[porsche930dude]

definately need to drive it to get it to settle down

[john walker's workshop]

The old bushings were well worn and there was clearance around them. The clearance is gone now, so there's your answer.

[brianlay]

I think new bushings would only account for 2-3 mm of lift, if that.
you were initially going for 12-13 mm of lowered height, what happened to that?

I wouldn't expect driving it to settle it that much.

You do have adjustable spring plates, right? IIRC, there is a range of at least 10mm of ride height adjustment there. I like to make sure that adjustment is centered before calculating the target angle for the spring plate.

The toe/camber adjustment will affect ride height but not more than a couple of mm, well within the height adjustment range.

[Mike_72]

Unfortunately this is on an early 911 without the adjustable spring plates. I guess I will take another stab at it. I am still baffled as to why the right side is sitting higher than the left when I has adjusted the spring plate 1 degree lower on that side..

[patz]

New bushings, non adjustable spring plates and you didn't count the splines right.....do over. Not you're the first person to do so. Welcome to the club. I've had my 356 apart maybe 20 times until I got it right.

My 911, adjustable swayaways.

[Mike_72]

Originally Posted by patz

New bushings, non adjustable spring plates and you didn't count the splines right.....do over. Not you're the first person to do so. Welcome to the club. I've had my 356 apart maybe 20 times until I got it right.

My 911, adjustable swayaways.

Can you explain what you mean by counting the splines? I basically used a combination of movements of the inner and out splines in order to achieve the desired unloaded spring plate angles. In my case I went with 33.5 degrees L/H and 32.5 degrees R/H. I did this with the car perfectly level as measured on the door sill.

[Reiver]

Mine did not 'settle' re indexed and re bushed. Drive it and see if that helps when you can.

[brianlay]

I think I understand your problem.
You shouldn't be depending on the angle of the car.
With the car on stands, you should take a measurement of the spring plate at full droop...there is one cover bolt that is in the way, but you know this.
subtract whatever angle that equals the ride height difference you're looking for.

Extract the torsion bars and adjust to the calculated angles for each side.
Put the wheels on and lower the car....you don't need shocks connected or even the spring plate cover.
Bounce the car (it will bounce very easily) and check ride height, I assume you're using fender lip?

re-adjust if necessary, but I bet you can get it right the first try. It only took me two tries with this method and I changed both bushings and put in stiffer bars!

IIRC the older torsion bars are limited to 50' minimum adjustment, approx 6.5mm ride height. you're not going to get any closer than that. The spec for max difference in height side to side is 8mm.

[Ducman]

The change in bushing from old to new and, i think from your opening post, also a different material probably create a difference from unloaded to loaded (one of the old bushings was saging/deformed more than other - it results in a sizable change to ride height) whereby you can no longer use your baseline measurements to count splines and get to the proper ride height.

I would set both spring plates to exact same measured angle unloaded, somewhere close to what you think is required, set it down. Measure new ride height then count splines to correct ride height and adjust.

Or replace SP with some adjustables and have it done in 5 minutes including time to swap spring plates.

BTW - keep in mind that the change in bushings has also changed your other alignment settings (toe / camber).

[Mike_72]

Originally Posted by brianlay

I think I understand your problem.
You shouldn't be depending on the angle of the car.
With the car on stands, you should take a measurement of the spring plate at full droop...there is one cover bolt that is in the way, but you know this.
subtract whatever angle that equals the ride height difference you're looking for.

Extract the torsion bars and adjust to the calculated angles for each side.
Put the wheels on and lower the car....you don't need shocks connected or even the spring plate cover.
Bounce the car (it will bounce very easily) and check ride height, I assume you're using fender lip?

re-adjust if necessary, but I bet you can get it right the first try. It only took me two tries with this method and I changed both bushings and put in stiffer bars!

IIRC the older torsion bars are limited to 50' minimum adjustment, approx 6.5mm ride height. you're not going to get any closer than that. The spec for max difference in height side to side is 8mm.

So basically my best plan of attack now is to take some measurements (fender lip to ground). Then jack car and unload spring plate, measure angle, determine desired drop and convert to angular measurement, make adjustments accordingly, re-assemble.

I still believe I will be ending up with 2 different angles side to side to achieve the same height.

[john walker's workshop]

Find a pair of adjustable ones.