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911 Torsion Bar Replacement

Pelican Technical Article:

911 Torsion Bar Replacement

Steve Jagernauth


4-5 hours






Floor jack, jack stands, wheel chocks, safety glasses, 11mm socket, padded pliers, large flathead screwdriver, grease, pencil, 19mm wrench, vise-grip pliers, hammer, protractor, tape measure, lug wrench, torque wrench

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 930 Turbo (1976-89)

Parts Required:

Front and rear torsion bars, rack spacers

Performance Gain:

Better handling for your Porsche 911

Complementary Modification:

Have the car professionally aligned, replace other worn suspension components as needed
     This article was written with the DIY'er in mind. Despite all the mystique surrounding this, torsion bars can be changed in your garage in a week-end with normal hand-tools. However, the rears take some iteration to get the HEIGHT right so plan on not using the car for a week or two in case you run into problems.

1. How large should I go?

     First, you need to find out what's the stock size for your car and the appropriate upgrade depending on intended use and your tolerance for the increased stiffer ride vs. the tradeoff in better handling. The following table lists stock torsion bar diameter in mm:

YearModelFront (mm)Rear (mm)

* some sources say 80-85 had 24.1 rear bars

     The formula for calculating spring rate is: k=d^4G where k=spring rate, d=diameter, G=modulus of elasticity (constant for steel)so ignoring the constant:

% increase in stiffness = ( (d2^4)- (d1^4) ) / (d1^4) * 100

where d2 is new diameter and d1 is original diameter

Here are some rate increases for earlier and later cars:

Stock Front = 18.8   

Stock Rear = 23   

Stock Rear = 24.1

21 mm : 55.7 %  

26 mm : 63 %  


22 mm : 87.5 %  

27 mm : 90 %  

27 mm : 57 %

23 mm : 124 %  

28 mm : 120 %  

28 mm : 82 %


29 mm : 153 %  


Some common combos are: 21/26, 21/27, 22/27, 22/28, 23/29 and 23/30.

     The smaller bars are oriented to combined street/autox/track use while the big bars would most likely be a harsh ride on real-world streets but provide great handling on the track. I opted for 21/27 for my Targa which was used for about 8 PCA Driver's Education events and 10 autox per year and street driven. I went with hollow 22/28 Weltmeister bars on my coupe due to its increased stiffness over the Targa and they both have a stiff but tolerable street ride. Talk to others or better yet, get a ride before deciding. If you have a pre-78 car, you should consider installing adjustable factory spring plates from '78-86 911 (pre-G50). These can be purchased used for $50-$100 and gives some ride HEIGHT adjustability. Better yet is the aftermarket Sway-a-way adjustable spring plate which allows finer adjustment of ride HEIGHT (esp. useful when corner balancing).

2. Installation

     This should be done with a full tank, tires correctly inflated and driver's weight in the car. First, measure the HEIGHT at the fenders front/rear. The factory spec from wheel-center to t-bar center will not help assuming the car will be lowered below Euro-HEIGHT. The car will be out of spec. You need to determine esp. at the rear how much you will be lowering so that it's still useable on the street. A good rule of thumb is you should be able to place your hand flat on the tire and feel the fender well on the upper part of your hand. I lowered mine approx 1" using this method. This is the limit for a car used on the street and you still need to be careful with driveways and speedbumps etc. You will also need to install steering rack spacers to correct for bump steer before alignment and optionally, corner balance the car. The rack spacers only cost ~$11.

2.1 Front Torsion bars

The front bars are mounted longitudinally inside the a-arm and are removed from the rear.

1. Place jackstands high enough to get under, leave wheels on. Remove underbody cover.

2. Remove torsion bars adjuster using 11mm socket.

3. Pry off rear endcap with large screwdriver.

4. Grab torsion bar splines with padded pliers/cloth and wiggle out from rear.

5. Grease new bars and install noting L and R markings for Left and Right sides.

6. Install new foam dust covers.

7. Install endcaps/adjuster, lower car and bounce suspension to check ride HEIGHT.

8. If car is still too high, turn bar clockwise to lower.

     Fronts were a breeze to install and adjust. Ignore the instructions you get and the Haynes manual. They tell you to remove too much stuff. You only need to remove the front t-bar cover if the bars are broken or rusted in place. Mine came out easily even with rust. There is a foam grommet over the bar to prevent dust. I got new ones from Stoddard at $3 each before I realized I could have cut foam into a circle with scissors and make a dust cover. I did the fronts with lowering in an hour. I didn't change any bushings. If you're doing bushings, expect to significantly increase your time.

2.2. Rear Torsion Bars

1. Place car fairly high on 4 jackstands so it's level. Mark jackstands so this HEIGHT will be constant. I put rear stands under the inner torsion bar tube. Obviously, can't use outer torsion bar cover.

2. Remove lower shock bolts.

3. Remove toe-adjuster eccentric bolt/nut (and lower droplinks if you have adjustable swaybars).

4. Remove rubber strip, rocker panels and round access cover for torsion bars.

5. Remove 4 bolts holding spring plate bracket (at outer torsion bar tube). Pry off bracket.

6. Use small floor jack to support weight of control arm and gently lower arm to lowest point to relieve spring plate tension.

7. Critical step: This is basis for HEIGHT adj. Use pencil to trace outline of upper spring plate on fender well to mark original position.

8. Remove camber adjuster eccentric bolt/nut on spring plate.

9. Remove 2 19mm bolts from spring plate to control arm and raise jack to support weight of arm.

10. Pry off spring plate cover over torsion bar. If the spring plate is stuck, either use a Visegrip locking pliers to hold torsion bar or you may need to tap the spring plate with a hammer to free itself from the torsion bar splines.

11. Remove spring plate and withdraw t-bar through the access hole in the body.

3. Now comes the fun part - setting the ride HEIGHT.

     The Porsche Tech Spec book lists the trailing arm angle as 36deg30'-37deg with each 1 deg change in angle resulting in 8-9mm change in vehicle HEIGHT. The torsion bar has 44 outer splines (1 spline=8deg10' and 40 inner (1 spline=9deg) therefore the smallest incremental change is 50' or about 7mm diff in ride HEIGHT. I measured the angles/ride HEIGHT before and after using a protractor and found that this method does not work if you change the spring rate. Using a change in angle of 6deg, my car still ended up being jacked up over 2" higher. However, through trial-and-error, I found that the change in untensioned spring plate HEIGHT resulted in similar change in ride HEIGHT but this will vary a little with spring rate. Therefore, I expect it will take at least 2 tries to get the ride HEIGHT right. It took me 4 tries.

12. Grease splines/bar liberally and install new t-bar noting L and R markings for Left and Right sides.

13. Install spring plate 1 " higher than base HEIGHT assuming lowering car by 1". Make sure both sides are same HEIGHT. Up to 1/8-1/4" side-side variance is normal. To change position requires rotating the inner end of the torsion bar 1 spline opposite to the spring plate.

14. Lower control arm and install bolts.

15. Install shock bolts to do a trial fitting.

16. Mount wheels/bounce suspension and check fender HEIGHT. Note correlation between change in ride HEIGHT and 1" change in spring plate spring plate HEIGHT. Car may be too low or too high on first try so you will need to reset the spring plate HEIGHT. Move the spring plate higher results in lower ride HEIGHT.

17. Lastly, get a good alignment. A good compromise track/street alignment is as follows:





-1 deg  

-1.5 deg


6-7 deg   




-15' (toe-in)

Comments and Suggestions:
chuck mmb Comments: Hi, I purchased these torsion bars 930 333 116 01 & 930 333 115 01. I'm installing them on a 76 911 targa. The splines inside the spring plates and the splines in the torque tube does not seem to match up. I know there is a inner and outer end but cannot get them to spline up. Any suggestions or are the torsion bars wrong for this car?
January 3, 2015
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you figure out if they are the right parts. I would start there. If I recall correctly, they should line up without trouble. - Nick at Pelican Parts  
Anton Comments: Hi Guys,
I have a 1969 912 in pristine condition and want to prevent
the rear torsion tube from rusting from the inside out. Some old timers filled it with oil or grease. What's the best method and where is the best location to put zerk fittings or drill holes to put 90w gear oil in. Thanks
May 4, 2014
  Followup from the Pelican Staff: I don't have any experience with the this. I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
carrera80 Comments: Hello,
I have a 1984 3.2 Carrera of which one of the rear torsion bars has broken. To replace both I ordered the 26mm Sway-A-Way rear torsion bars. I removed the broken torsion bar; however the remaining part of the bar still remains in the tube. Does anyone have any tips on how to remove the remaining part of the broken rear torsion bar? Tips are much appreciated!
September 30, 2013
  Followup from the Pelican Staff: How far up the tube is it? You could find a 12 point socket just small enough to bang over the bar, then put a locking extension on it and pull it out.- Nick at Pelican Parts  
Roby466 Comments: This could be a year difference or simply due to the fact that a 930 is slightly different than a 911 but to remove the front torsion bars, I absolutely have to remove the whole a-arms from there as they won't clear the floor pans on a 1985 930.
January 22, 2012
  Followup from the Pelican Staff: Thanks for the input on this one. - Nick at Pelican Parts  
Jrboulder Comments: After looking at PET and other sources it looks like late MY 1976 and all MY 1977 cars had adjustable spring plates The article says all pre-78 cars don't have adjustable spring plates.
Part # for non-adjustable: 901-333-003-01
Part # for adjustable: 911-333-009-00
Cars with a VIN # greater than or equal to the following have adjustable spring plates:
91162 01872
91162 11898
91163 01741
91163 11425
91166 01021
91166 10439
91260 01838
93067 00641
93068 00493
June 21, 2011
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. - Nick at Pelican Parts  
dangerous brian Comments: hi i have a 1977 carrera 3 targa. i have pulled out the broken part of the torsion bar but dont no how to get the other part out any ideas ? regards brian
May 15, 2011
  Followup from the Pelican Staff: Try knocking it loose using a long punch or prybar. Once it breaks free, you should be able to work it out with a strong magnetic tool. - Nick at Pelican Parts  
jerryw Comments: I have a 1975 911 targa. When I hit a hard bump I hear and can see where tire and finder scrape. Is this a torsion bar issue?
March 24, 2011
  Followup from the Pelican Staff: Could be a number of issues. I'm going to copy this question to the forums and our members there will be able to provide additional help. I would personally check the shocks first, and also check to make sure that you have the proper wheels and tires installed on there. - Wayne at Pelican Parts  
912'68c-10'66Riv'63 Comments: Steve, or anyone else...
hey i have a similar situation i picked up my 1968 912 for FREE! friend of my dads... anyway my passenger side torsion bar is busted i assume as the car dosent suport itself in that corner. if i follow the instuctions and remove the "t-bar" cap, i suspect the half of it exposed will come of easy. but how am i supossed to go about getting the other end still in there out?
March 3, 2010
  Followup from the Pelican Staff: Try knocking it loose using a long punch or prybar. Once it breaks free, you should be able to work it out with a strong magnetic tool. - Nick at Pelican Parts  
pipe dreams Comments: Hi guys, i have a 74 911 targa with 20mm sway bar in front and am missing the rear bar, can anyone tell me what bar i should have in the back. I would like to do a lot of fast mountain driving and use it as a daily driver, and an ocassional track day at Infineon
January 4, 2010
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need. - Nick at Pelican Parts  
skip Comments: Can you show me a link discussing the interchangeability of rear trailing arms, spring plates, and torsion bars. I have a 1969 912 and might be able to obtain a 1986 set, or a 1987 set. Thank you.
December 24, 2009
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need. - Nick at Pelican Parts  
Scott Comments: Wayne, Thanks for the hint. I should have mentioned that after i bought the car, and while she was down for the engine and tranny rebuild, we raised her back up to Euro-Spec, so she is not lowered any longer. I guess he may have put some stiffer torsion bars in it, but I did not see "any" new parts anywhere else, as he had neglected nearly everything. If the car was slammed for a "LONG" time, could the torsion bars get worn or loose their ability to re-coil? This is my first Porsche rebuild. I have restored lots of cars, but nearly all have been old American Hot Rods. I am really digging this old 911SC. It handles great, other than the light bounce over any little bump.
Thanks again for your expertise!
October 9, 2009
  Followup from the Pelican Staff: Sorry, it's nearly impossible to say over email - I'd have to drive the car. - Wayne at Pelican Parts  
Scott Comments: Hello,
I have a 1980 Porsche 911SC with 98000 miles. When i bought it, it was a basket case. The guy before me had lowered it as far as it would go, and let the maintenance go. It would not hardly shift or run... I have spend a year restoring the car to where it is now. Engine / transmission rebuild. Numerous interior upgrades and a fresh coat of paint. Lastly, New Koni Shocks. alignment and wheel balance.
My question is concerning the suspension.
The car kinda does this light to moderate bucking or bouncing, unless under acceleration or braking. It is not the engine at all, I think I have isolated it to the suspension. A bumpy road really gets is started bouncing up and down and it makes for a kind of jerky ride.
I replaced the shocks, thinking this was it. My last two options, as far as I can discern, would be torsion bars, and then possibly new tires. The wheel balance i had done, was a force-wheel balance, and the tech told me two of the tires were not perfect, but he did the best he could. I have to say, that before the force wheel balance, the steering wheel started jumping around and the wheelss started hoping around anywhere north of 55 mph. The alignment and force wheel balance has gotten the car to a much more driveable place, but this bucking still persists, and I have to sort it out!
Can you tell me, what are the symptoms for worn out torsion bars? Is there an other logical thing that could be causing this bouncing, or bucking?
Thanks in advance, for your expertise!
October 8, 2009
  Followup from the Pelican Staff: If the car was lowered down, then it might be experiencing bump steer, which jerks the wheel a bit back and forth when you go over bumps. This is because the geometry of the suspension changes just slightly when you lower it. The solution is $30 bump steer spacers that raise the steering rack back up to a proper height. This is detailed in my 101 Projects book. Seeing how you said the previous owner had lowered it all the way down, I think this is probably your problem. I don't think it's torsion bars, unless someone put stiffer ones in at some point in the past. - Wayne at Pelican Parts  

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