So these things are getting old. The newest ones are 41 years old! Of course mileage comes into play. I am not taking into account your rubber bushings have sagged to the point your torsion bars are grinding against the a arm (very common). Let's go with an optimum, best case scenario: no grinding and 130k miles and 41 years old. Do they loose there ability to work through there range of motion as intended? Sag?

Here is an interesting article on the subject; I've wondered about this also.Click to view attachment

The paper is a bit over my head. My son would understand the calculations but I just zipped to the conclusion. My gut feeling is that while the torsion bars will eventually fatigue, most of the other moving parts will wear first so the bars are sort of the last thing on the list, unless they are rusty, cracked or worn.

How rusty is too rusty? I was going to post a pic of one of mine when I got closer to suspension work on my resto, but since the subject has come up... The rear bushing had obviously leaked on one and pitted the surface just a little. Not sure whether to repaint and reuse. I had a torsion bar break on my first 914. It broke while parked, which I've read is common. I've no issue with walking out to the garage to find a sagging corner on the car. Less thrilled about the idea of snapping one during a hard corner.

I was told if they have rust on them, replace them. I ordered a new set, from Sway Away, in the stock diameter.

I blasted Michael's / Cairo's old ones, powder coated them and plan to use them on my suby build.

Glad they found life in a new build.

I didn't know they had stock diameter. I thought it wsss only 21, 22, 23.

Funny - I had the same things happen to mine. Drove, parked - all was good. Returned to find a sagging right front corner. I had no idea that they were more likely to fail while stationary. Interesting.

Worn out bushings let the bar rub, then the rust starts. Friction and rust then take over.

I think the state of the rubber bushings determine the lifespan more than anything. Once they deform and allow the bars to rub, the lifespan shortens. Luckily, Sway-a-way provides replacement bars (either solid or drilled).

I can't imagine sag being a thing on 914s --- too light. Plus they are easy to adjust so you would never really know if the PO did or not.

I know sag is an issue on first gen 4wd Nissan Pathfinders and Hardbodies around 200k miles. But that's not surprising when it's taken into consideration that 2/3rds of their 4000lbs are on the front axle and offroading is hard on suspensions. Even coil springs sag with that kind of use.

I've had one rear that snapped on a 911, it did have large rust pitting.
IRS beetle it tells you to lightly coat with grease before installing.

dp

If you can polish out the rust pit the bars should last much longer. Re-paint with a good rust proof coating.
It's when a pit leads to the initiation of a stress concentration crack that they fail.
The corrosion almost always starts when the rear bushing deteriorates and lets the bar rub in the ID of the A arm and cuts thru the protective coating. then rust pits start

Each time we got in a 356 we always ordered NEW bars. They are not expensive, they improve the ability of the suspension to work in harmony with the other NEW bits.

It's like using 40 some year old springs..........They are DOA as springs start dying after ten years and they don't get any better as they age.

Buy New bars and rubber bits........be done with it.

Around 78" , got out of the 70' and sat down in a lawn chiar facing the car 10 feet away, with-in seconds of sitting down...."SNAP" short sharp snap noise, and very quickly left frt was slightly lower. I had no idea what happen. But since I was in my driveway, figered it out and replaced both.
I have stored a set for years, and after owning, and driving many 914, this has never happened to me again. Sitll waiting to use them.

Elephant Racing has 19 through 25mm. Not sway away. I wonder if they have the 914 spline count?

If I wanted new bars Sway a Way would be my first call.
https://swayaway.com/

that’s where we buy most of our torsion bars and rear axles.

One of mine was broken when I bought the car, so 30 years is my guess

thanks for the tip. It's worth a shot. I'm thinking polish and powder coat.