Snapped Mount - Tarett swaybar
 

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About 2 years ago a well respected local shop installed an adjustable Tarett front swaybar on my '88 Turbo S, which is a mostly street driven but I also run 2 or 3 track days a year. The suspension is the factory M30 with Fabcar steel A-arms and 968 castor blocks.

Early last spring, I noticed some front end noise while turning, and I was very surprised to find that one mount for the swaybar had snapped and the other was badly bent. My initial thought was that something bound up as there is not a lot of flex in the mounts and there is no rubber or urethane - the bearings are all steel on steel.

The folks at Tarett were very nice and sent me replacement mounts, which I installed and carefully checked to ensure that there was no binding. All good, or so I thought.

Fast forward to yesterday, and I was at an open track event at NY Safety track (great little track with lots of turns and elevation about 50 miles south of Cooperstown). The car never felt planted and after checking underneath, I discovered that one mount had again snapped, and the other was badly bent. Pretty much the same as the original situation. I took the bar out and ran some laps, but needless to say, it was less fun with no front swaybar...

So I have a note into the good folks at Tarett, hoping to get some insight as to what might be causing the issue. The car has not been abused at all, and the only thing that I can think of is that there may be too much torque on the mounts when I jack up one side of the car (from the midpoint jack pad under the door).

Wondering if anyone has dealt with something similar, or may have some insights.

the torque might be the factor - the sway bar still needs to twist along its entire length to work. if torque (clamping) is too high the bushing/bearing deforms and acts like a clamp on the bar too.

Well I must be losing my memory. I posted when I had the original problem a year or so ago, but just realized that now.

That does not help my problem, but I can confirm that the recent issue is identical to what happened a year ago.

rennlist.com/forums/924-931-944-951-968-forum/1057502-tarett-front-sway-bar-broken-mount.html

The one thing that I am wondering is whether the Fabcar A arms are upside down (and switched right to left). The ball joint is a monoball so when I refreshed the bushings and pins a couple of years ago I could have put them on the wrong side. I imagine that would alter the swaybar geometry.

Im Running That Exact setup Tarret Bar and Fabcar arms.. BUT I am Running about 800 Lb Springs on the front, So my suspension isn't moving as much, combine with the Intrax Struts, and my car "Leans less" right off the bat. When I Initally put my bar on I didn't like it... I don't like the way when you move the heim joint forward it almost takes the "Twist" out of the bar and really puts major stress on the mounts. In the future I will be changing my bar to something else just for that reason.
My take is that you have a heavy bar (or are running it tight) and stock type springs making the sway bar carry a Really heavy load and because the springs are light the bar gets adjusted to its "Tighter" setting putting even further load on the mounts. I don't run mine much past 1/2 way on the slides.
I don't see how flipping the arms could cause this issue because they are symmetrical and they would be equal on both sides. Where the real stress is when you roll into a corner and one wheel goes up and the other goes down and the bar fights that. with softer springs that is compounded Esp if you are running sticky tires.. I just don't care for the design. The bar end links need to be longer so they are right on top of the hole where the Drop links go. This way the bar twists like its supposed to and doesn't load the mounts.
It has been recommended to me by a prominent racer that I ditch that bar and go to a 968 MO 30 bar. The Stock Turbo-s bar is 26.8 mm and the 968 is 30mm Combine that with solid bushings.. should be good.

Thank you GPA951s - your insight is very helpful.

I suspect that my configuration is further stressed as the car has AC, and therefore I am mounting the bearing blocks on the lower holes of the Tarett bracket. That would seem to exacerbate the load on the bracket in several ways: i) moving it further away from the frame rails, ii) having an additional hole in the vertical of the mount (with that hole becoming the weak spot where it snapped) and iii) to your point - increasing the angle (vs fully vertical) of the end links.

Once I get the replacement mounts from Tarett I will pay careful attention to the geometry of the end links, both in an unloaded and loaded position. Hopefully, I can get to something that is workable.

Lindsey Racing just recently starting selling their billet front SB mounts separate from their "M035" kit. Might be worth a look if you haven't already.

https://www.lindseyracing.com/LR/Por...44-HDFSBM.html

[QUOTE=Porvair;15938771]Thank you GPA951s - your insight is very helpful.

I suspect that my configuration is further stressed as the car has AC, and therefore I am mounting the bearing blocks on the lower holes of the Tarett bracket. That would seem to exacerbate the load on the bracket in several ways: i) moving it further away from the frame rails, ii) having an additional hole in the vertical of the mount (with that hole becoming the weak spot where it snapped) and iii) to your point - increasing the angle (vs fully vertical) of the end .

What is the front spring rate? What is the diameter of the rear torsion bar? Please provide and then I can comment if the Tarett sway bar is a good application for your current suspension.

Those Lindsey pieces look very nice - thank you for the link.

T&T - I am running stock M030 front springs and rear torsion bars. I am considering going back to the stock M030 front bar and welcome your thoughts. The car is not a dedicated track car - mostly street driven with 2 or 3 track days a year (on high performance street tires).

I would then recommend selling the Tarett sway bar.The Tarett is very stiff for a stock spring rates and thus overpowers the suspension in roll leading to the bracket failures. The Tarett sway bar is for a car that rolls less than 3 degrees and yours with stock front springs rolls more than 3 degrees.

Porsche designs the car with understeer. Making the front end stiffer, ie stiffer sway bar, only makes the car understeer more. If you want to have a better handling car for the track, contact Jason at Paragon Porsche Products for assistance.

I removed them from my race car even though my roll is less than 3 degrees, have front spring rate of 500 lb/in because the front sway bar was to stiff, limited adjustment, and caused understeer. My rear torsion bar is 30 mm