Torsion Bar Installation Question

[Mike Feinstein]

Snagged a new set of torsion bars....22's and 28's for my 89. I'll be having them installed but I'm just curious....

I see that they are labeled L and R. Which side is L? Depending on your orientation it could be either one.

Also, which end of the bar faces out (closest to the perimiter of the car), the end with the label (stamp), or the blank one?


Thanks,

[ChrisBennet]

The number of splines are different for the inner end and outer end - so no worries about putting them in backwards. As far as left and right, I can't see why there would be a difference - there isn't on Glen Sander's bars IFIK.
-Chris

[Zeke]

I'm really sorry to disagree. The number of splines are the same and the one marked left goes on the driver's side as it is pre-stressed for the usual single driver. I don't believe it make any difference as to the direction of the bar. See top paragraph on p. 162 "101 Projects For Your 911."

IMHO left and right are always determined while sitting in the car (facing forward for you contorsionists).

[Chuck Moreland]

Left is the drivers side.

However, the ends of the tbars do not have the same number of splines. It is the difference in spline count that allows very fine adjustment of the rear ride height (on early cars without adjustable spring plates). You can dial in a rotation of the tbar that is much smaller than a full spline!

It is therefor impossible to install them backwards (inside out).

I don' t know about the pre-stressed thing. I suspect that they test the spring rate at the manufacturer to be sure it is in spec. The spring rate may not be the same in both directions, therefore they are marked left and right to be sure you install them in the same direction they got tested.

So do be sure and keep the correct L/R orientation.

[marcesq]

L=drivers side. R=passengers side. Chris is right the number of splines on the inside is different than the number of splines on the outside. If there were the same number of splines on both sides then it would be imposible to adjust the ride hieght.


edit: Chuck types faster than I so

[pbs911]

The fronts have the same # of splines on both ends but must still be installed according to L and R.

I hear the torsion bar can snap if the L is installed on the R side, and visa versa.

[marcesq]

Thanks for clearing that up Paul. I should have mentioned that, but was responding to the rears only based upon the ride hieght adjustment.

Cheers

[911pcars]

Chris,
I agree with your assesement of the rear bars. However, L and R might refer to the front torsion bars which (if memory serves me), have the same splines on either end. Used bars take a "set" in their installed postion and should thereafter be used in the same L or R location.

Sherwood Lee
http://members.rennlist.org/911pcars

[DavidH]

I just put mine in last night. The Left is the drivers side and I put the stampings to the front or as you reference towards the perimeter of the car. They seem to fit fine and I was able to set the height to 25.5 inches from the fender well to the ground fairly easily with only a couple of attempts. I will takle the rears this weekend as the new neatrix are going on. Then off to the alignment shop.
Good Luck...

[Mike Feinstein]

Thanks guys. I just looked at the bars and confirmed that the rears have a larger diameter at one end than the other. Fronts are the same so I'll follow the L&R-only routine for those.

Best,

[marcesq]

David:

The fun is just about to begin for you. (Bin there done that)

Mike:

Follow the R & L orientation on the rear as well

[Zeke]

Originally posted by marcesq
Thanks for clearing that up Paul. I should have mentioned that, but was responding to the rears only based upon the ride hieght adjustment.

Cheers

And I, unfortunatley, was talking about only the fronts. Much apology. Looks like it's cleared up now, though.

And I don't know where I read up about the pre-stressing, but if I can find it again, I'll post it. I'm always willing to back up any statement or have a big slice of humble pie. UMMMMM..........GOOD.

[APKhaos]

Mike,
You are going to LUUUUVE it. Just finished upgrading to 31/21 with street hardness polys all round, corner balanced and aligned for dual purpose street/track. First drive tonight, and its beuutiful - radically improved turn in and responsiveness. The biggest surprise is that there is none of the harshness I was expecting - the ride is smoother on this setup, which is certainly due to the fact that every single stock bushing was totally shot [at 150K miles, thats no surprise].

FWIW, I learned a lot about bump steer geometry in the process. Bolting on a kit spacer is a [very] rough approximation. It well worth spending the time to carefully measure the tie rod angles, and make a spacer that gets the tie rods to perfectly level - makes a huge difference. The next step is the very spendy ERP drop link kits, which Jack O has on his car. Perfection, at a price.

Should manage to get the new sways on next week [big Smart Racing rear, Weltmeister front].

Now, I think you will find that some after market torsion bar manufacturers DO pre-stress for L and R - if so, the bars will have an identifying mark for the correct side. Chris B is right - the Sanden gun drilled bars are not factory stressed.

[ChrisBennet]

Originally posted by APKhaos
Mike,
You are going to LUUUUVE it. Just finished upgrading to 31/21 ...

APKhaos,
Is 31/21 what you meant to write?
Chris
'86 with 22/29's

[APKhaos]

Chris,
Yes - 31 drilled [hollow] Sandens rear, 21 solids front. Revalved shocks, street poly bushings, sway bars as above. Beautiful!

[Vipergrün]

Originally posted by APKhaos
Chris,
Yes - 31 drilled [hollow] Sandens rear, 21 solids front. Revalved shocks, street poly bushings, sway bars as above. Beautiful!

So, this sounds like a great way to get rid of understeer, huh? That's a larger spread than I've typically seen. Will the drop link kits be mandatory to complete the package? I've been thinking about a very mellow 22/26 setup with stock sways.

thanks
-Brad
80SC

[ChrisBennet]

Originally posted by APKhaos
Chris,
Yes - 31 drilled [hollow] Sandens rear, 21 solids front. Revalved shocks, street poly bushings, sway bars as above. Beautiful!

Hi again,
If the 31 is the measured size of the hollow bars that would make more sense. A hollow 31 would be equivelent to something like a 29 or 30. I think stock sizes in '85 were 18.8 and 24.5 so if your bars were really 21f/31r the fronts would be 1.55 times as stiff as stock but the rears would be 2.56 times as stiff as stock - a pretty weird combination!

If you want to play Torsion Bars, the Home Game. Here's how:
Stiffness of a torsion bar increases with the 4th power of the diameter i.e. twice as thick is 16 times as stiff (=2x2x2x2).
Stiffness increase = (new bar thickness / old bar thickness) ** 4
18.8->21 = 1.55X
24.5->27 = 1,.47
24.5->28 = 1.71X
24.5->29 = 1.96X
24.5->31 = 2.56X
Note: '86 cars had 25mm rear bars. If you used that number, a 28mm rear bar (1.57X) would be great match for a 21 front (155X).
-Chris