bronken torsion bars

[DohertyCM]

I have a 1988 Porsche 930

It puts out about 410HP with about 450lb torque.

It has broken 2 torsion bars. The were upgraded to the hollow 30mm bars.
The car has broken 2 of them on the right side.
As far as we can tell the only thing that could be breaking the bars is Torque....

Would the solid bar be better...
Would the softer 28mm or 26mm better for spring action...
Should I remove the bilstein shock and add a coil over in its place to help with the
torque effect?

Looking for some ideas and answers before I replace another bar....

Chris

[Quicksilver]

The engine torque can't effect the torsion bar unless it caused the suspension to go to full deflection. Suspension travel is the only force on bars.

Cracks can be caused by stress risers (scratches), corrosion, poor quality, or just plain dumb luck (least likely). Are the bars completely unmarred on the surface? Are they greased or protected from corrosion in some other manner? What brand are the bars?

There is nothing wrong with hollow bars but I would only use Sander or Elephant bars. I would also stay away from the Sway-A-Way bars as there are more reports of those cracking.

As far as the size: The rear size should be relative to the front size and is simply based on how much firmness you are willing to take in trade for handling.

[agrimmitt]

I would agree with Quicksilver, hollow bars are strong and just fine (I have and looked for a long period of time for Gary Sanders bars>front and rear) and are the type suggested by almost everyone. I don't have your hp, but I believe you don't have my suspension set up. Couple of questions, who indexed them at installation (happened twice now) and did you afterward have the car corner balanced. Do the bars show any corrosions from dirt or maybe salt? Third is the car lowered and is the camber modified heavily negative? Last are you running stock rims 16" or wide 15" rims in the rear.
art

[Dave Colangelo]

+1 for protecting the bars with grease or some thing. I just did my rear bushings and did a good deal of reading on this matter. From what I understand you can replace the whole torsion bar system with coil overs if you like. That may be something to consider if you are willing to spend the money. From what I have read the coil overs are a direct replacement for the torsion bars not some thing that assists them. Although there has been talk of them being used together to get very high spring rates.

When they were replaced did you re-index the suspension?
What bushings are you using (original rubber/netrix/poly graphite/oil)?

Regards
Dave

[safe]

Elephant Racing bars = Sander bars
But I think ER are plated.

[DohertyCM]

Yes the car on the last install was indexed and corner balanced.
The rear tires are 315/30 18 on an 11" porsche rim. Came from a 996 I believe
The bushings I dont remember what the mechanic put in there...There was
talk of solid race bushings. But I will not know for sure until I get it all apart.
The Torsion bars are the hollow type..and they are white from what I remember.
I will look at the elephant bars...But I will look at the cracks and corrosion when I get it out.

Chris

[Porboynz]

Are they breaking in the same place, inboard or outboard? Right on the spline or in the middle? eg Maybe the spring plate is the issue if they are breaking on the spline outboard end.

[Steve@Rennsport]

Originally Posted by DohertyCM

Yes the car on the last install was indexed and corner balanced.
The rear tires are 315/30 18 on an 11" porsche rim. Came from a 996 I believe
The bushings I dont remember what the mechanic put in there...There was
talk of solid race bushings. But I will not know for sure until I get it all apart.
The Torsion bars are the hollow type..and they are white from what I remember.
I will look at the elephant bars...But I will look at the cracks and corrosion when I get it out.

Chris

Chris,

If they are painted white; those are Sway-a-way bars and they did have some heat treatment issues as I've seen this before.

I'd recommend installing Sander bars or Chuck's ER ones as they are made in the same place. Good stuff and nary a problem as long as the bushings are in top condition to prevent any rubbing.