I was talking to a group of guys and a couple stated that sway bars wear out and need replacement. I have a driver 69 442. I have replaced the front bushings and parts, I have never considered the sway bar itself, front or rear, being bad. Should I. It hasn't crashed, so they aren't beat up any more than normal wear for a car that old. Thanks

 

They probably do, but very unlikely they'll wear out in normal everyday around-town & highway driving unless accompanied by extremes in temperature (huge variances and great frequencies of these huge variances), corrosion (salt & the like, etc.), extreme & repeated stress. One area I managed in the USAF (you'll find the exact same methods employed in civil aviation) was aircraft isochronal inspections which include several types of NDI (Non Destructive Inspections). These inspections are critical to the analysis of many systems of an aircraft and the ability to predict problems (these types of inspections are key to many other devices, as well). You can think of a simple SOAP inspection as a form of an NDI. At any rate, you can lookup isochronal inspections, NDI, etc. and find significant amounts of literature. Bottom line is I doubt a normal sway bar (in particular a solid sway bar as opposed to a hollow sway bar) will require replacement based upon normal driving conditions. If you're punching a car through radically extreme cornering and/or drag strip hole shots on a very regular basis I'm sure there's some wearing occurring with greater frequency.

 

You probably should hear from an engineer specializing in metals. Bars that have been distorted in crashes, exposed to intense fire, suffered severe corrosion, etc. probably would need replacement. Springs and torsion bars sometime lose their torsional capabilities with age. They are likely exposed to greater torsional loads than the sway bars. My "guess" is that bars used on street driven vehicles in normal circumstances wouldn't need replacement.

 

The sway bars are just mild steel, no different from the frame or rear axle housing or suspension arms. Other than minimal wear where the bushings and end links attach, there is no wear. Metal DOES fatigue due to cyclical loading, but unless the part in question had an inherent flaw that grew, you'll never see fatigue failure in normal driving. That's a long way of saying "no".

 

......... and an engineer appears.

You might want to check the sway bar in another 50 years.
.....Just my two cents worth.

 

It wears out when it becomes 2 pieces.

 

its worn out when they fatigue and crack thru the mounting bolt holes..

 

Agree w/ you, Mark. In fact, a quick review on the World Wide Web demonstrates images and areas where sway bars have worn & failed, such as those areas susceptible to holding water/moisture (salt) for extended periods of time i.e. sway bar rubber bushings, mounting hardware, etc. - all increasing the effects of metal fatigue in select areas. Those areas (like most areas where items are likely to corrode) should be pounded w/ waterproof grease.

https://www.google.com/search?q=brok...w=1920&bih=976

 

Corrosion isn't "wear" any more than rust on the frame or body is "wear". Sure, if rust thins the metal, it can and will lead to failure. This isn't "wearing out" any more than rust on the bottoms of your front fenders is "wearing out". It's rust.

 

It isn't wearing out as what might normally be construed as metal fatigue due to stress (in and of itself w/ all other factors being equal and not influencing metal fatigue). None-the-less, it does demonstrate where sway bars have worn and broken as the result of extenuating (external) factors such as water, salt, etc. - which, I would argue, does increase the wearing of the metal. I would further argue, corrosion is a form of "wear" - in particular when two dissimilar metals contact each other yielding to corrosion. That is the fundamental and basic operation of corrosive properties. The rapidity of transferring ions between dissimilar metals increases corrosion - the fundamentals of any Redox equation.

 

Sorry, but I have to disagree. "Wearing out" implies failure due to normal use - either from fatigue failure of the metal due to normal cyclical loading or from relative motion between parts. If your cylinder walls have to be bored oversize after 100,000 miles, that's wear. If they have to be bored because they have rust pits from sitting around in humidity, that is NOT wear.

 

Understood. For the sake of eliminating a perpetual diatribe regarding useful definitions of "wear", I'll concede what you describe (above - cylinder walls having to be bored) as abrasion wear. What I describe as wear (regarding the Redox potential of two dissimilar metals) as corrosive wear. Both, IMO, are forms of "wear".

 

While that is technically correct, it is not the commonly used definition of "wear", at least not among motorheads. To get back to the O.P.'s question, do sway bars wear out? No. Can they rust out? Yes.

 

OMG, I was ready to concede; yet, I would argue it depends on who you're talking to and the manner in which they refer to something "wearing" out. I'll bet half of those polled would suggest their rocker panels are wearing out while the other half would say they're rotting out, or they're corroding. I only brought up the images to demonstrate where sway bars were wearing out based solely upon images - not necessarily based upon definitive empirical research and the etymology of the term "wear".

 

Corrosion on to components rubbing together can contribute to excessive wear. Such as the bushing areas. But I submit that the wear is so slow, it's like getting round rocks out of the river beds. They wore down SLOWLY over a long amount of TIME.

But unless something was wildly out of alignment or excessive corrosion to eat away something, normal wear and tear just keeps the metal contact areas with the rubber bits clean, shiny and smooth. That's about the extent of the wear even after decades. It's probably more likely you'll see the dreaded lip seal wear groove on your harmonic balancer than you will seeing the sway bar fall out from under the car because it wore out.

I agree, maybe 50 years from now, that same sway bar with the same rate of use may be wore slap out. But I'll be wore slap out before that, so I think you're good.

 

Ha, ha!!! I have been around for a loooong time and I have never heard of a rocker panel "wearing" out.

Rusting out...always.

Sometimes The Queen wears me out...but, a much different context.

 

Wear is this conversation going?

 

I dunno, but I'm pretty worn out from reading through it.

 

It's really not a question of conceding, nor is it a poll-able question. Mechanical wear and metal fatigue is not corrosion, galvanic reaction, embrittlement from radiation, or etching from battery acid. These things have precise engineering definitions.

All that being said, I doubt you would cold work a sway bar to any sort of performance problem. A loose connection might deform the mounting holes, but you would lose the bushings in the hold down clamps long before fatigue.

 

Thanks for the opinions, I think. I didn't mean it to take off. I didn't think that they wore out under normal circumstances. That being said, I've been wrong before.

 

Mark Donahue wrote about skid-pad testing of race cars in his autobiography. He describes a car that had excellent handling for a couple of laps, and then began to not hold the steering input. They determined that the sway bars were improperly heat treated, the material was yielding instead of maintaining proper tension. (The bar was bending and losing spring tension.) An upgraded heat-treatment of the replacement parts solved the problem.

Do sway bars wear out? Not typically. Can they be over-extended and bend? Sure, but again not common. Can they be subject to metal fatigue? Again, yes, but it's not something that folks see a lot of. MOSTLY, automotive sway bars are as reliable as the sun coming up. The rubber bushings that hold them in place are NOT.

I worked for a company that built City Buses. There is a Federally-recognized, State-sponsored Bus testing facility nominally based in Altoona, PA. The specially-developed test tracks are outside State College PA.. Our company's bus was being tested, must have been 1993. They drive it up and down the test track, potholes, speed-bumps, elevation changes, left turns, right turns 24 hours a day, until the bus breaks. Then they report the failure and wait for parts to be shipped so they can fix the bus and resume testing. One of the problem areas was sway-bar breakage. I was sent to State College to look into the problem, and to "light a fire" under the testing folks. I looked at the pile of broken sway bars, they all broke in the same place, they all looked like fatigue failures, the bars all broke at the usual 45 degree angle, with the usual "beachhead" marks. I was sending photos and descriptions back to the Engineering department. They told me "don't bother" we break sway bars all the time at the test track, but never on buses in revenue service (actual on-the-road, passenger-carrying use.) Evidently, the "torture track" was a little too much torture!

https://www.altoonabustest.psu.edu/index.aspx

 

Wearing out, well not exactly.

Some cars had hollow bars and water would get inside of them and rot them out from the inside.

Also keep in mind that the older the car, the more rust and rot it could have.

I did replace the front sway bar on my Delta about 2-3 years ago now. Bar was actually for a 70-81 Camaro and I picked up a brace bar for a 75-77 Cutlass (i think, could be the 73-74 Cutlass but I'm 99% sure it was for a 75-77) All UMI stuff

Both were a direct swap as well as the stock ZQ8 S-10 bump stops I installed. None of these parts I replaced were broken or rotted out and the car was over 30 years old. The end links, well they snapped the second I applied a little force to them

 

In aircraft terms corrosion is not wear. It is a chemical break down of the metal. In other words being exposed to water,salt,and other chemicals. Steel is no different in that process and will pit,exfoliation will happen. I doubt very many round steel sway bars have that problem unless extreme conditions exist.

 

This thread about torsion bar wear is getting twisted.

 

Funny!

 

Thread on my device says do sway bars wear out.

 

I had a rear sway bar snap on my 79 H/O, loud thump/bang underneath as I turned into a steep driveway. Car suspension twisted pretty good due to degree of the gutter I suppose. Don't remember exactly where on the bar the break was but I assume near the mounting point.

 

There are ways of testing sway bars. This is one on YouTube, caution annoying music.

 

Does anyone kow where to find a sway bar for a 75 Delta 88?

 

I didn't think sway bars (anti roll bars to UK residents ) were made from mild steel. They would be bent a little every time the car went round a corner above walking pace, and I don't think they would put up with that for long. Leaf springs and coil springs - which are torsion bars coiled up - settle over time, and they are made from sterner stuff than mild steel. Of course road springs are subjected to a constant one way load.
Having said that Shurkey in post #21 told us that commercial bus sway bars can be made to fail, but not in normal service (I'm guessing over huge mileage), So in the real world if your sway bars don't have wear from friction in their mounting bushes or corrosion damage and it isn't a race car seeing regular track time don't sweat over it.

Roger.

 

Sorry, you are incorrect. Metals have a yield strength and an ultimate strength (and also a fatigue strength - more on that later). Yield strength is where the metal is permanently deformed. Ultimate strength is where it breaks. So long as you keep the load below the yield strength, you can bend the metal and it springs back with no ill effects. Heat treating increases the yield and ultimate strengths, which allows more load or deflection before yielding, but so long as the application is designed to keep the load below the yield strength, mild steel is just fine. What matters for an anti-sway bar is the stiffness of the metal, and all steels, whether heat treated or not, have about the same modulus of elasticity and thus the same stiffness.

Fatigue strength is the load at which a metal part will break after being subjected to repeated loading - think of bending a paper clip. This is typically specified as an S-N curve (stress vs number of cycles), since the number of cycles to failure depends on the load - the lower the load, the more cycles a part can withstand.

 

Thanks for correcting me Joe. Are road springs made from mild steel too?, I didn't know that.
I came across a British 1 ton van that had composite rear springs, a single leaf of what looked like glass fiber. The original Mini's had rubber cone suspension, then a system involving hydraulics (Hydrolastic was it's registered trademark) and air suspension is commonplace on big trucks and buses nowadays. So I guess any elastic medium that works will do.

Roger.

 

No, spring wire is typically heat treated because it deflects more in uses and in that case mild steel would reach the yield stress.
Composite springs are not unusual. Corvettes used composite transverse leaf springs on the C4 through C7 generation cars.

 

Doesn't seem to be an overall "leaning" in either direction on this discussion...

 

Related article

https://www.hagerty.com/articles-vid...wsletter_NewDD

 

Great article, thanks.

 

Yes thank you, They make a sway bar for my truck...was unaware. Thanks again.