Front torsion bar question

[bugstrider]

Car: 1978 SC

Hello all,

Lowered the front of our 78 911SC and installed a bump steer kit provided by our host. Equal height on both sides of 25" and had it aligned.

Problem #1:

On occasion, in sweeping right curves that have a slight dip, I will hear what I describe as a split second tire rub coming from the l/front tire. I have small cuts on the outboard edge of the drivers side front tire supporting the fact it gets rubbed on occasion.

Problem 2:

I reinspected the front end and noticed that when the car is on jack stands and the front wheels are hanging unsupported, the left front or drivers side torsion bar adjustment bolt and cover is loose enough I can wiggle it with my fingers and move it freely up and down causing a audible clinking sound. The right front/passenger side is rock solid. No noticeable sounds while driving either.

I have a small video clip but don't know how to attach to the thread. I was able to post the video on YouTube so here is the link. Please keep in mind that it was taken at night while laying in scorching asphalt in cramped conditions. You get the idea.....

http://youtu.be/OqN21gMSqd4

Question:

Obviously, does anyone have an idea why the torsion bolt and tube cover would be loose enough to have that much free play? And, could this free play contribute and allow the front end to dip enough to contact the tire? Has anyone experienced a broken or aged out front torsion tube and if so, are my symptoms common?

I have a video clip of me moving it about. I also attached my GoPro onto the fender and filmed my drive into work on HWY-49 this morning in an attempt to see the body roll or tire contact with the fender. A fun twisty two lane highway with dips and risers. Got the tire to rub the fender only once so I hopefully can see the fender travel as well. Nearly hit a buck, so I'm really interested to see that part too. It was probably farther away that it looked at the time, but when driving hot through the curves, it looked like it jumped over the front fenders. Had I hit the darn thing, then this post would be a mute point.......lol

Cheers Trevor

[Flieger]

All sounds normal to me. You can roll the lip on the inside of your fenders, and/or add more negative camber, and/or raise the car, and/or go to shorter tires.

[Chuck Moreland]

The adjuster mismatch indicates you may have the corner balance incorrect. You didn't mention corner balancing the car, which should be done when changing the height. The height can be perfect and the corner weights way off.

And roll the fender lips.

[johnsjmc]

I suspect the loose vs tight adjuster with the wheels drooping indicates a low or high corner opposite at the rear.
Are the same number of threads showing on the adjusters ? There is a simple way to check corner balance .Look up "tripod balancing". basically you lift the car at the rear in the middle (engine parting line works) and measure your front heights. They should be equal . Then do the same by lifting in the middle of the front (approx. center under crossmember ) and measure the rears. With all 4 corners being adjustable the 911 has vast possibilities for optimizing adjustments, but the same adjustment options can also result in an unbalanced car. Extreme unbalance can still exist in a level car but panic stopping will lock one front before the other(The light corner will lock prematurely)

[Flieger]

How about a picture? From your description I figured that both wheels were off the ground and so both of the adjuster bolts had lost contact with the crossmember, but one was still snug on the splines and the other was loose.

[Trackrash]

One of the adjusters is indexed differently that the other. Probably won't make a difference, as long as the corner balance is in spec.

What size of tires and wheels are you running? What are the alignment specs, particularly the front camber.

You may want to consider rolling the front fender beads.

[bugstrider]

I was able to post a link for the short video clip via YouTube in the original post. Here is the link as well:
http://youtu.be/OqN21gMSqd4

Here are some shots if the tires.







Tire size is a 205/50R16
Federal brand that came in the car when we purchased it


Sent from my iPhone using Tapatalk

[Flieger]

That is a lot of play. Probably want to look for a used adjuster and see if it is more snug on the splines.

I am assuming the whole A-arm is not moving when you do that (because of how easily you can move it). If the arm does move with the adjuster then your bushings are shot.

[bugstrider]

Originally Posted by Trackrash

One of the adjusters is indexed differently that the other. Probably won't make a difference, as long as the corner balance is in spec.



What size of tires and wheels are you running? What are the alignment specs, particularly the front camber.



You may want to consider rolling the front fender beads.

Tires are a 205/50R16 that was on the car when we picked it up. I'll try to get a copy of the specs too. As far as rolling the fender, that has been explained how to do that. However, I'm curious as to why I am rubbing only on one side. I'll admit that due to me being behind the learning curve, I didn't consider the ramifications that lowering the front would have on the corner balance topic. When I discovered the loose adjuster nut on the same side as the rubbing tire, I now wonder if there is another underlying condition working its way to the surface.

Cheers Trevor

[bugstrider]

Originally Posted by Flieger

That is a lot of play. Probably want to look for a used adjuster and see if it is more snug on the splines.



I am assuming the whole A-arm is not moving when you do that (because of how easily you can move it). If the arm does move with the adjuster then your bushings are shot.

I agree, in my limited experience, it seems a little excessive. The A-arm itself is rock solid and shows no movement. The only thing that wiggles around is the adjuster nut and t-bar cover plate. That is, when the tires are hanging freely unsupported .

Cheers

[trond]

with the front on the jack but tires still on the ground my adjusters are loose too and I suspect the adjusters move in/out and cause corner balance to go out of adjustment. Driving at brisk pace on bad roads the front does not feel settled but seem to float about enough to resemble an 70s Volvo with bad shocks. Vigorous work with steering wheel required. Tires are new Bridgestone S-02N3, a-arm bushing new ER rubber and shocks newish Bilstein HDs. Something is not right

Rather than rolling fenders I would suggest you try the S-02N3 which are narrower than most other tires on the market. Solved my rubbing issues and by far the best tires I have tried. At least for sporty driving

[johnsjmc]

I still believe you have an unbalanced car. If you didn,t corner balance already.
In your video it appears you have a several more threads sticking out on the loose side. If you wound in that adjuster (to match the tight side )it would probably tighten like the other side.
Then you would put the car down and find one side up front to be high. This says the opposite rear corner is low or soft and you have compensated by altering the front instead of the back where the solution is. Before you change anything .Try my suggested tripod measurement If you lift the rear in the middle at the engine seam and measure the front heights I expect you will find the heights aren,t equal anymore.

[bugstrider]

I'll give the tripod measurement a try. I remeasured the height to the bottom of the front fender and now am sitting at 24.75" on the drivers side front. WTH!!

When starting out with the tripod measurement are lifting from under the engine case directly? Via a block or pad of course.


Sent from my iPhone using Tapatalk

[johnsjmc]

You can use a small piece of 2x4 as a pad if you are nervous but I just lift on the seam without anything extra..When you lift at the middle at the rear you look for a difference side to side at the front. A 1/4 in isn,t much but says the left front is set softer than the right front. If you check the rear balance by lifting at the center of the front crossmember you will likely find a similar soft corner diagonally opposite the soft front.
The car can be made to sit level with 4 wheels on the ground but you did it by cranking down the front instead of lifting the opposite rear corner. It,s often done because front adjustment is so simple, but isn,t always the correct place to adjust. An unbalanced car can pull on braking or prematurely lock up one side first.
I have corner balance scales but rarely use them I can get pretty close to balanced with the tripod measurement method. certainly good enough for most street driven cars. Best measuring point isn,t the fender lip either , but it,s quicker than using the factory reference points under the car. Try and measure on a flat concrete garage floor and set tire pressures first. A soft tire can affect the measurement by 1/4 in too.
To adjust the car .Set the fronts equal with the rear on a single point and then adjust the rear to be equal same way.The rear adjusts by loosening bolts and eccentrics on the trailing arm and is more trial and error than the front.
If the tire rubs on the soft corner the soft spring (TB) setting is contributing to the tire being pushed deeper into the wheelwell on a bump. Your loose front adjuster is also likely on your soft (low) corner too ?

[Trackrash]

Originally Posted by johnsjmc

You can use a small piece of 2x4 as a pad if you are nervous but I just lift on the seam without anything extra..When you lift at the middle at the rear you look for a difference side to side at the front. A 1/4 in isn,t much but says the left front is set softer than the right front. If you check the rear balance by lifting at the center of the front crossmember you will likely find a similar soft corner diagonally opposite the soft front.
The car can be made to sit level with 4 wheels on the ground but you did it by cranking down the front instead of lifting the opposite rear corner. It,s often done because front adjustment is so simple, but isn,t always the correct place to adjust. An unbalanced car can pull on braking or prematurely lock up one side first.
I have corner balance scales but rarely use them I can get pretty close to balanced with the tripod measurement method. certainly good enough for most street driven cars. Best measuring point isn,t the fender lip either , but it,s quicker than using the factory reference points under the car. Try and measure on a flat concrete garage floor and set tire pressures first. A soft tire can affect the measurement by 1/4 in too.
To adjust the car .Set the fronts equal with the rear on a single point and then adjust the rear to be equal same way.The rear adjusts by loosening bolts and eccentrics on the trailing arm and is more trial and error than the front.
If the tire rubs on the soft corner the soft spring (TB) setting is contributing to the tire being pushed deeper into the wheelwell on a bump. Your loose front adjuster is also likely on your soft (low) corner too ?

+1
I would like to add that to be most accurate you should have the sway bar disconnected. I realize that is a pain on the SCs. But you can get a good idea of your corner balance without disconnecting the sway. After each adjustment and before any measurement, bounce the car up and down to settle the suspension.

The way I have done my car is to set the rear torsion arms at exactly the same angle. Then adjust the fronts as described above.

That said, from your video, it looks to me like that front torsion adjuster is unusually loose. If it were my car, I would investigate the cause, and make sure that nothing else is loose.

I had the exact same issue with one tire rubbing on one side of my cars front end. Turned out to be a loose ball joint.

[johnsjmc]

I wouldn,t bother disconnected sways just yet. The tripod method is quick and dirty compared to scales. I do it before aligning any street driven 911. If a long way off it will still show with the sways connected. The closer you get to balanced the less effect the bars have(unless one is bent).
After identifying if balance is the problem the owner has the option to seek a balance using scales (ideal but more$)or continue to adjust with tripod measurement.