Rear Sway Bar Snapped! Anyone Else Had This?
 

Just went out for a quick spin and found as I reveresed out of my mates drive I heard a clicking from the rear!

On inspection I found the drivers side of the rear sway bar has just sheard through!

I purchased the seay bar kit about 3 maybe 4 years ago, its The Racers Group and there thickest version the 25mm too!

I had to install WEVO rear sway bar mounts because the factory ones ripped but i never thought the 25mm solid sway bar would ever break......

Has anyone else encoutered this?

Think I may go for an Elephant rear sway bar now.


I cabled tied the droplink etc up so I could get home...

http://forums.pelicanparts.com/uploa...1305381611.jpg
http://forums.pelicanparts.com/uploa...1305381650.jpg

I haven't read of this happening. Your bar asm. is aftermarket, the material and heat treat process could be different than a factory part.

Gavin,

Yikes ... good thing you weren't enjoying some spirited driving at the time !
I would say you can't go wrong with Elephant parts as Mr Moreland has a solid reputation
for carrying quality parts and is very active on this forum !

Could have been worse :)

Cheers!
Phil

wow

Hi Phil SmileWavy hows it going? Its the weekend so time for a nice pint of the black stuff;)

Its going to be an expensive month for me....new front pads, bearings and monoballs, after the monoballs went on I found the Weltmiester strut brace didnt work with monoballs, so just ordered Elephant triangulated strut brace........and now need a new rear sway bar LAMO

Think I may just get all my suspension bits from Elephant, at least I know it all works together.

I've just emailed The Racers Group, so I'll see what they say..

Hey Gavin,

It's raining here for the next 3-4 days so i'm going to go over my car thoroughly this weekend,i have a two day DE next week so i don't want any surprises.

It's up on stands now so i'm going to go play garage for a few hours :)
I have a lot of ER stuff on my car and the quality and support from Chuck is next to none !
As far as the Weltmeister strut brace goes,one of my brackets cracked so i welded it up for now because i needed a track alignment and couldn't wait for a replacement but i was looking at Steve Wong's strut brace and it's a nice piece of work.Should one of my brackets crack again i'm strongly considering it ...

As far as the black stuff goes,i will hunt down JJ and claim my Guiness from him ... lol

Good luck with your car,it seems like it's going to get a lot of goodies !

Cheers!
Phil

Metal fatigue or a flaw in the grain structure.

How long is a sway bar (torsion bar) guarantee? Maybe the Racers Group will provide some out-of-warranty support, but you know about products designed for racing environments. They're a professional org. and race team, not likely to produce shoddy goods.

FWIW:
- 25mm is pretty hefty for all but a late 911 or a track car? What's the rear torsion bar size?
- The great Jim Clark died when the rear sway bar broke on his Formula car. Breakage happens.

Sherwood

Why is there all that rust around the shiny break? It looks like the bar had a groove to about 1/2 the outside diameter in it????

A hollow bar would be even less reliable.

Very interesting.

I have seen broken weltmeister bars. As sherwood suggests; what torsion bar are you running? You really should keep things cleaner. Racing parts are not designed for daily driving and a little rust will cause a part to break prematurely.

rust fissure is just like a stress riser

When is ordered the sway bar from TRG I spoke to Austin there and went through the tires/suspension specs and told him the car is just a spirited sunday driver and maybe the odd track day. He said with the cars spec's etc the largest 25mm is fine.

Torsion bars - standard as far as I know.
Shocks - Bilstien Sport
Wheels - 18x10 (rear)
Tires - 265x35x18 (rear)
WEVO engine & trans mounts

Even with cleaning I dont think i'd be able to clean just where its snapped, its up against the drop link and the blue block that bolts to the ARB mount. Unless I disassemble it all and clean it!
Maybe powder coating it would have helped prevent rust.
Still seems strange that what seems to be a high end part designed for the riggers of racing should rust and snap, if thats what caused the problem.

So what is recommended for a mainly street car that wont fall apart?

I disagree with the comments that racing parts would be more susceptible to this type of failure due to rust/dirt. Metal bars are metal bars, regardless if they are designed for racing (technically metal bars are not just metal bars due to differences in metallurgy and heat treatment, but a "racing" bar is not treated different when it comes to rust prevention). Racing components that are not designed for street longevity tend to be things like bushings/monoballs or very lightweight parts.

My guess, given the picture of the failure, is a manufacturing defect or poor material. Its difficult for me to see, but the failure looks to be more of a brittle type failure - this shouldn't happen with quality material. I'd show it to the manufacturer and see what they say - hopefully they replace it. A proper sway bar should be designed to accommodate the full range of suspension travel the given 911 without reaching into a fatigue zone in torsion or bending (this shouldn't be too difficult for any higher grade steel). This range should be accommodated regardless of torsion bar size. A Smaller than normal torsion bar balance will cause your sway bar to twist more often, but again, the stress levels seen should be low enough with proper materials and design that fatigue failure isn't an issue.

That said, a friend of mine had his sway bar crack on his BMW 550. So, s&*t happens. Inspect stressed components more often if you are driving hard.

Thats too much sway bar for stock torsion bars.

Race cars are usually maintained better and don't see too much wet weather.

I know of another TRG sway bar that broke, but Mike's was his front bar I think. Looked exactly the same at the break too. But if I'm not mistaken, TRG uses the same bar front and rear, just different hardware. That car was an '87, 23/33 torsion bars, Fox shocks front and rear. Wonder if there's been some metallurgy issues with the TRG bars?

i don't necessarily disagree with you. I've seen sway bars and t-bars that were totally rusted and didn't fail. But these were stock applications where stress were low. I'm not saying rust caused this failure, just saying rust doesn't help and can promote a failure just like a stress riser.

PO:
How is your torque arm connected to your sway bar? Given the picture, this could have been slightly loose allowing it to score the sway bar. At some time, or some point in the travel it could have seized up transferring torque through the now weakened, smaller cross section bar. This would be mre likely to fail.

I saw a friend at the track yesterday and he told me he broke 2 rear sway bars on his '87 Carrera with a 3.6 swap. He was running 28mm t bars in the rear and later upgraded to 31mm. (I used to bottom out on the track with my 28mm bars, btw, and so I went to 30)

I think stock T bars allow so much roll the sway bar is stressed. I'm also pretty sure he mentioned his bars were the same brand.

[QUOTE=gavinc69;6021643]Just went out for a quick spin and found as I reveresed out of my mates drive I heard a clicking from the rear!

On inspection I found the drivers side of the rear sway bar has just sheard through!

I purchased the seay bar kit about 3 maybe 4 years ago, its The Racers Group and there thickest version the 25mm too!

I had to install WEVO rear sway bar mounts because the factory ones ripped but i never thought the 25mm solid sway bar would ever break......

Has anyone else encoutered this?

Think I may go for an Elephant rear sway bar now.

Aside from the noted popping you heard, what was felt in the driving of the car (while it was broken)?

Doyle

As Ed correctly stated, I broke a 25mm TRG bar on my car. Twice. The car is an '87 with 23/33 torsion bars and Fox shocks, just as Ed stated. ~2750 lbs with me in it, and primarily used on the track. I run the bars on the stiff side in front and the soft side in back. In both cases it was the front bar that broke, but the same bar is used front and back. The first bar broke essentially the same place (see below)
http://forums.pelicanparts.com/uploa...1305461859.jpg

The second time it was the weld holding the solid hex plug in the hollow bar:

http://forums.pelicanparts.com/uploa...1305462000.jpg

Did I feel anything? Yes! The first time was in the carousel at Mid-Ohio and I was able to catch the rear end as the front suddenly had more than expected grip. I knew immediately that either the front bar or the linkage for the front bar had broken. The second time was more of a gradual break, as the hex plug still encountered considerable resistance to turning after the weld broke, so the bar "sort of" worked. I spent the full weekend trying to get the car to handle right, and ended up with the front bar set nearly full stiff before I took it all apart and discovered why...

The first bar survived ~10 years of heavy track use, so I felt I had no complaint. The second bar did not last its first weekend. TRG acknowledged it was defective and replaced it gratis.

Thanks for all the input guys.

I didn't feel any difference in the driving but I was only driving in a normal fashion to my friends and then obviously very carefully on the way back.
I think the actual break occured whilst reversing out of his drive because its got several different cambers on it (it goes down then up whilst all so on full lock) so that was probably the straw that broke the camels back.

I need to get the sway bar sorted before June 3rd as myself and car are off to Europe for a week around the Alps (so glad it didn't break then, there's some very high drops off those mountain roads!)
Once back I will look at getting some front & rear upgraded torsion bars (they where on the long list of things to do anyway) as hopefully that may aid in taking some stress off the sway bars (although the TRG sales person did say it would be fine with standard bars!)

The car also only does 3K miles per year, so its not been caused by excessive use.

After seeing that there is a hex plug welded to the bar, I have a theory that the weld's heat affected zone may have left some untempered Martensite which cracked and then propagated that crack. Proper heat treatment of the whole bar could temper the bar but was it done? Properly?

Think mine also snapped off where the weld is! Must be the weakest point.

Hopefully TRG get back to me tomorrow.

I think it can be said that aftermarket part manufacturers are likely to not provide as complete an engineering spec., testing and process control as is typically found in factory parts. They probably would like to but the market will not pay for it. Some are better than others. It is not the end of the world, the part breaks you fix it or get another one and get back to enjoying driving your Porsche.

That TRG bars looks exactly like the Tarret I bought from Elephant, just different colors.

Who exactly makes these?

"...Wonder if there's been some metallurgy issues with the TRG bars?"

Hmm. Typically, post-welding heat treatment or surface treatment (e.g. shot peening)? Wasn't aware welded ends is a common practice. Most torsion bars I've seen are machined/swaged from a one-piece billet, but I don't get out that often.

No excuse at that price point to not manufacture a torsion bar properly.

Sherwood

Tarret uses square ends, this TRG is hex. Other than that they are copies of each other.

on the Tarett site under sway bars....

"All components are designed and manufactured to the highest quality standards, resulting in the finest and most reliable swaybar on the market."

and
"Optimized geometry for bind free operation throughout the entire suspension range of travel."

so there should be no binding issues backing out of a driveway

Given this, there must be an issue on their side, I'm sure they will be glad to replace it.

Then there is this on the Tarett site. Given that these parts are generally for cars used in competition (not daily drivers), it might be difficult to test in under 30 days unless you schedule race days and parts buying carefully.

WARRANTY
All products are fully warranted against defects in material or workmanship at the time of receipt. Claims must be made within 30 days from the date of the receipt.

@Mike 87 911

On the TRG website I see this picture, I'm thinking the notch is there because if just plain welding of the hex in the tube.... the weld would be a weak point and subject to failure. Does your weld have that notch on the other side?

http://forums.pelicanparts.com/uploa...1305501286.jpg

The front Tarrets are not notched like that.

+1

Many times parts don't even get installed int he first 30 days; sometimes not even for a couple years.

Why not just buy the Smart Racing bars and be done be done with it? In my opinion they are the best I have seen.

Actually, the TRG bars are copies of Tarett (Pelican sells Tarett).

I have had both and the manufacturing and design of the Tarett is superior. The devil is in the details: The Taretts are thicker where they should be, on the contact zones on arms and bushing blocks. There is a plug weld at the end of the bar, this is where the bushing contacts the bar so it must be smooth to reduce wear, on the Taretts the weld is complete and machined smooth on the TRG it isn't. The bushing blocks on the TRGs are double drilled to be universal, but the holes are so close together that there is virtually no material between them. The plating and anodizing is better on the Taretts. TRG uses a nut and bolt to secure the arm instead of an internal thread, the bolt can drag and get damaged. Overall I just think the TRGs are a little rougher. I guess that is to be expected since making parts like this is just something TRG does on the side and not their fulltime business.

Here's some pictures I took a while back of a rear bar:


http://forums.pelicanparts.com/uploa...1305509528.jpg
http://forums.pelicanparts.com/uploa...1305509534.jpg
http://forums.pelicanparts.com/uploa...1305509540.jpg
http://forums.pelicanparts.com/uploa...1305509546.jpg
http://forums.pelicanparts.com/uploa...1305509551.jpg
http://forums.pelicanparts.com/uploa...1305509556.jpg
http://forums.pelicanparts.com/uploa...1305509561.jpg

Cory is right. Much to the dismay of Ira (Tarrett Eng), TRG copied his bar. The little changes they made looks like it effected the reliability.
I'm very glad I have the Tarret units.

I think all of Cory's comments are right on target.

:eek:

Whoever designed that TRG bushing mount with the siamesed holes is no engineer, and should be fired!

There are just a couple of comments that I would add:

The first photograph showing the failure is very clear and it is due to corrosion fatigue.

When a short fatigue crack develops in a material and there is water present the crack growth rate will increase quite significantly due the the pH at the crack tip.

The 'fresh' clean surface of the fatigue crack is very active and wants to oxidise very quickly so it pulls an oxygen atom from the water and increases the hydrogen ion concentration.

If you do an experiment with a fatigue crack immersed in distilled water you will find after about 20 minutes the pH at the crack tip is around 2.5-3.0.

This acidic liquid accelerates the crack grwth and sharpens the crack tip.

I would say, looking at the photograph that there was a prior defect and the corrosion helped it along.

Looking at the later photograph of the welded part it is surprising to see that the force applied to the sway bar is transferred by the weld.

The fatigue crack will almost certainly have followed the maximum stress and putting a weld t this location is not the best idea.

If you look at a basic document such as'20 Golden Rules for avoinding fatigue failures' putting welds into regions of maximum stress would be quite high up the list.

I am not sure what material is being used but it is unlikley to be a spring steel.

I think you could make such a bar by welding but you would need to use a technique such as friction welding but it would be difficult to have the opposing ends in the correct orientation so I have come to the conclusion it is better to machine from solid.



The fatigue

I have broken the mounts before but never the bar. Quite interesting when it happens, especially when you are flat out comming out of a corner.

I can only imagine what it would be like at speed breaking the bar..........

@Chris_seven,
Interesting I didn't know regarding the localized pH. Thanks for that.

My guess regarding roll bar design is assuming the bar surface is near some sort of fatique stress limit trying to "grab" it via a smaller diameter using a weld is likely to put one in trouble without going through considerable engineering and test. I think your comments suggest this also. This may be why the Smart Racing bars have plain ends connected by only a clamping type approach. For similar money I predict the Smart Racing system is more durable.

So far my stock bars are working for me so I haven't tested any of the aftermarket bar systems.