Do anti-roll (sway) bars wear?

[Cornishman]

Any views on "if an anti-roll-bar wears over time"? Coil springs appear to soften over time, so the theory suggests that a torsion bar would do the same. Any metallurgists out there?
There are many discussions on matching anti-roll bars back and front, with relevant sizes, but if they wear then it is time to buy a new pair if adding a rear bar. This is my current dilemma, so wondered if there was a view or better still a consensus!
C

 

[Mike Goble]

Springs are under tension 24/7. Swaybars basically just sit there until you turn a corner. The duty cycle on sway bars is considerably shorter.

 

[Arde]

Under high load I believe sway bar spring rate gets weaker. Though the main
concerns are bushings first, and breakdown second.
For proper design street use I believe spring rate is constant.

 

[x_atlas0]

If the roll bar is corroded (rusting) it can change the spring constant due to point thickness differences. Saw a late 50s car going through a corner with a very rusty undercarriage and the sway bar snapped right in the middle of the turn.

From a purely materials standpoint, though, I would be surprised if it changes that much just due to time. Typically, it would need to be loaded and/or hot for extended periods to seriously alter the spring rate.

 

[Mike Goble]

The average wire diameter used in coil springs is about half the sway bar diameter, for example my Bav has .6" wire in the front springs and 1.125" wire in the front sway bar. If you made the springs from the same wire as the sway bar they would go from about 140#/in to over 2200#/in. If you had these 2200#/in springs on your car you would be hard-pressed to detect any sag in their old age.

 

[Arde]

... If you had these 2200#/in springs on your car you would be hard-pressed to detect any sag in their old age.

Such springs would last forever but your dentist may need to redo your tooth cavity fillings every year...

 

[johanaxelson]

Also, the swaybars are quite seldom under a load. Metal will tire the most when it actually is under a load, springs tire for example are under constant load and movement. And they *do* tire.

 

[Honolulu]

Correction...

Suspension springs are continuously torsionally loaded, not compression or tension. But we all knew that.

"Anti-sway" or "anti-roll" bars are also torsionally loaded, but as noted above, only intermittently.

 

[mpetry912]

The rubber bushings definitely wear and get old / cracked with age. Replacing sway bar bushings is inexpensive and worth the trouble. I don't think that the sway bars themselves wear noticeably. However they might snap under load if heavily corroded

Mark Petry
Bainbridge Island, WA