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911SC Rear Steer Collapsed Right Side Rear - Bad Rear Control Arms? ExcessiveToe Out?

I thought for sure I saw threads about this but after 10 minutes of searching I am at a loss and can't find them. To the issue: I am getting like a squirrely fish-taily feeling in the rear, like the rear is steering itself (known as "rear steer" right?) sometimes randomly on a straightaway under even just slight acceleration. Also I think visually the right rear seems collapsed somewhat (collapsed is too strong of a word...lower than the left but not completely collapsed) and probably wearing out on the inner side of the right rear tire. I've heard this is caused by a few things but it would great if someone could call b.s. or said politically correctly since we're in the political season right now, could someone leverage their expertise and experience for the benefit of this poster by eliminating the least likely causes and perhaps illuminating the most likely causes?

Note that tire pressure is good

Is it most likely to have rear steer because:

1) Bad Control Arms
2) The fact that it's collapsed - But then why is it collapsed and what would need to be replaced?
3) Bad bushing or bushings - If so, which?
4) Bad rear alignment
5) Something Else - What?

Thanks for any help as always!


Last edited by octanemaestro; 07-20-2016 at 04:27 PM.. Reason: Typos
Old 07-20-2016, 04:24 PM
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Don't drive the car. Lift it up, and look. Rear end on these cars is super simple, if it broke you can see it.

Good luck
Old 07-20-2016, 05:00 PM
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My guess is that it is going to be the inner rear bushings. These are not too difficult to replace however, you will have to remove the rear training (banana arm) to do this.

When I replaced my rear bushings, the old bushings crumbled apart when removing. The new bushings raised the car about 2" and have made the steering much more precise.

Here's a few pics of my rear bushings. I replaced with Elephant Racing Sport Rubber bushings. This project could easily be done in a weekend or just a day. Car should be re-aligned afterwards.

Old Bushings vs. New:


Pressing in the new bushings using Bolt & Washers:


New Bushings Installed:
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Old 07-20-2016, 05:42 PM
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Broken torsion bar?
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Old 07-20-2016, 08:30 PM
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My barely educated guess is bushing wear closer to the wheel, like torsion bar bushings. no way to know w/o looking, push and pull on everything and look for movement.
Old 07-20-2016, 08:30 PM
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Hi...If the rear side has actually dropped, then you have a torsion bar that has broke. If it has all of a sudden just started to sway back and forth, then I would suggest that you have a look at your banana arm bushings. Maybe they have 'collapsed' as in being completely worn out along with your other rubber bushings, such as your spring plates bushings; it possibly could even be a tire that is beginning to separate.

I have never heard of it happening, but I guess that it may be possible that the vulcanization of the rubber bushing on your spring plate/torsion bar has let go.

To begin with though, it would be best for you to jack your car up and remove the rear wheel so as to have a good look at all the the bolts/nuts, including your bushings on both the banana arms, including the spring plates.
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Old 07-20-2016, 08:56 PM
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Just a bit more of an explanation for you...The torsion bars have splines at each end. You can lower or raise a 911 by rotating the torsion bar to a different spline position. If the torsion bar was to break, which can happen, then the suspension will drop as there is nothing to hold it in position.

3.2's have an adjustable spring plate that will let you raise or lower the side about 3/4's of an inch max if set at the very bottom or visa-versa.

SC's don't have adjustable spring plates so that would eliminate this bolt with a cam on it from being broken. It would be highly improbable for this to happen anyway. So again, if it has actually dropped in height, I would tend to put my money on a broken torsion bar... Others may be able to suggest something else.
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Old 07-20-2016, 09:24 PM
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Thanks for all these explanations. I don't have a good jacking surface right now but I recognize I have to get under there again and yank and feel around. I had the wheels off recently while getting new tires (because belts were showing on the inside of this SLIGHTLY dropped right side (it's not collapsed all the way)) and I didn't see a broken torsion bar then. I thought the worn tire replacement would help, like someone said above it can just be a bad tire causing rear steer but it still rear steers SOMETIMES (not always). When you talk about broken torsion bar I imagine a dramatic drop and I don't have that. It's maybe 1.5% lower on this side where the tire was wearing out. And the rear steer is not constant just occasionally. It's akin to the feeling of accelerating slightly too fast on an oily smooth wet asphalt until you take your foot off the gas pedal and quickly regain traction.

Let me ask you...with a big old American car when you have something in the suspension worn out like tie rod ends or other bushings the mechanics tell you it's not dangerous but rather it's just uncomfortable (jerking or wandering) or noisy (clunk.....clunk clunk) but you're not going to ruin something until you fix it because it's all very strong metal. Is it the same case here with the rear steer with driving the car up to say 40 mph here and there?

Last edited by octanemaestro; 07-21-2016 at 01:14 AM..
Old 07-21-2016, 01:11 AM
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I've seen no mention of rear wheel bearing in this discussion so far, so I'm just going to throw that out there...
Whatever the issue is.....Do not drive the car until it is corrected !!
Old 07-21-2016, 02:32 AM
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Spring Plate bushing
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Old 07-21-2016, 02:59 AM
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Quote:
Originally Posted by A horse with no name View Post
Just a bit more of an explanation for you...The torsion bars have splines at each end. You can lower or raise a 911 by rotating the torsion bar to a different spline position. If the torsion bar was to break, which can happen, then the suspension will drop as there is nothing to hold it in position.

3.2's have an adjustable spring plate that will let you raise or lower the side about 3/4's of an inch max if set at the very bottom or visa-versa.

SC's don't have adjustable spring plates so that would eliminate this bolt with a cam on it from being broken. It would be highly improbable for this to happen anyway. So again, if it has actually dropped in height, I would tend to put my money on a broken torsion bar... Others may be able to suggest something else.
SC's have adjustable spring plates. First thing I thought was that the cammed adjustable spring plate bolt is loose.

I would immediately take it off the road and trouble shoot the suggestions made on this thread.
Old 07-21-2016, 03:40 AM
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Sorry about that... SC's do have adjustable spring plates as 'will hung' has just stated. As 'will hung' also stated, take it off the road and fix whatever it is.

Your reference to your car rear steering; 'wandering' from either the front or from the rear, is a definite sign that you have worn out suspension parts. BTW, you can not see a broken torsion bar.

Most alignment shops will have a look at it for you free of charge. So if you can't jack it up to check it out yourself, then take to an alignment shop that specialize in Porsche suspensions. 911's do not have a complex front or rear suspension. Different - yes, but they really are quite a simple system.

For you to learn more about Your suspension: Elephant Racing | Suspension Navigator | Porsche 911/912/930

Just hoover over the yellow circles with the letters for an explanation of the part.

When you find out what the cause is, just post it, as it would be interesting to see just what it was.
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Old 07-21-2016, 11:51 AM
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Quote:
Originally Posted by A horse with no name View Post
BTW, you can not see a broken torsion bar.
I have to think if you put the rear in the air with the wheels 6" off the ground you could then lift the wheel from the control arm - near the wheel.

A broken torsion bar will offer no resistance and the wheel will rise but the car will not go along with the wheel. It's essentially your leaf spring.

Like I said, this is thinking - NOT experience. Plus only two beers into it.
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Old 07-21-2016, 12:17 PM
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I would say broken rear sway bar mount or broken torsion bar.
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Old 07-21-2016, 12:20 PM
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Quote:
Originally Posted by octanemaestro View Post
<<< snip >>> When you talk about broken torsion bar I imagine a dramatic drop and I don't have that. It's maybe 1.5% lower on this side where the tire was wearing out. <<< snip >>>
Surely this is a typo (!) I don't think you would - or could - spot a one-and-a-half percent drop in one side compared to the other.
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Old 07-21-2016, 01:51 PM
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Surely this is a typo (!) I don't think you would - or could - spot a one-and-a-half percent drop in one side compared to the other.
Yes, it's a typo. 1-1.5", not %. One to One and a Half Inches not percent. Thanks for catching that.
Old 07-21-2016, 02:23 PM
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Here is the pic from the elephant website - the red saw line is where it would break back in the torsion tube. You could not see the break unless you removed the torsion bar from the torsion tube.

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Old 07-21-2016, 02:49 PM
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