Torsion bars Options

[Cvrguy]

Just pulled mine out of my '73 today as I'm replacing the suspension bushings. Both bars are slightly abraded due to the very old bushings deforming (old? I hardly had to heat the retainers in order to get them off!). Replace or not? Mine measure a little over 18mm at the shaft (18.01 and 18.25mm to be precise. The difference may be in the amount of paint on the bars). I've checked the usual sources but no luck as yet. Who might carry them? I really don't want to increase the spring rate with the 20mm ones from Pelican.

If I clean these up, are they useable? Can they be reversed? Does the minor abrasion significantly change the spring rate? Are those from the early 911 of that era an alternative?

While i'm at it, one of the adjuster screws shows signs of starting to split. Replace?

[bajafreaks]

What is the deciding factor on when to replace the torsion bars? Looking at the pics from the original post they dont look too bad. I didnt realize they were so critical of a component.

[Superhawk996]

What is the deciding factor on when to replace the torsion bars? Looking at the pics from the original post they dont look too bad. I didnt realize they were so critical of a component.

Torsion bars are a highly stressed spring where the outer heat treated layer is where the highest stress is concentrated. The center of a torsion bar does virtually nothing which is why you can have hollow torsion bars.

When the outer hardened layer is compromised by corrosion, scratches, or gouging it creates a very localized stress riser where cracking will begin. Eventually the crack will propagate through the bar and the bar will fail catastrophically.

This isn’t speculation. It is an engineering reality. Having a bar fail will ruin your day.
Typical failure:


The bars in the 1st picture are scrap.

[Cvrguy]

What is the deciding factor on when to replace the torsion bars? Looking at the pics from the original post they dont look too bad. I didnt realize they were so critical of a component.

Torsion bars are a highly stressed spring where the outer heat treated layer is where the highest stress is concentrated. The center of a torsion bar does virtually nothing which is why you can have hollow torsion bars.

When the outer hardened layer is compromised by corrosion, scratches, or gouging it creates a very localized stress riser where cracking will begin. Eventually the crack will propagate through the bar and the bar will fail catastrophically.

This isn’t speculation. It is an engineering reality. Having a bar fail will ruin your day.
Typical failure:


The bars in the 1st picture are scrap.

After cleaning up the replacement torsion bars, I had the LCAs and other bits sandblasted to prepare for painting. When attempted a trial fitting into the adjuster end, They don't fit! Was there a change in the number of teeth on the torsion bars over the model years? The original bars fit fine. ???