Rear Anti Roll Bar Mount Reinforcement??

[1974carrera]

I'm thinking of reinforcing the rear anti roll bar mounts in my '74...thought I'd reinforce the original ones before they fatigue and rip out. Has anyone used the Smart Racing reinforcement kit to do this with the existing old-style mounts still in the car? An alternative is to use the the updated mounts with the wishbone reinforcement but it seems like more effort to remove the existing mounts and weld in the new ones than just reinforcing what's there. Plus the updated mount can have the 8mm nuts rip out, which is what the Smart Racing reinforcements try to solve, so I'm thinking why not just reinforce what's already in the car. I'm also interested in hearing about any other good alternatives that may be out there for reinforcing the rear mounts.

[89911]

You are correct in your thinking. The mounts should be reinforced in 2 ways. One, is to fix the entire mount from failure. The "improved" mount does this, but in a minor way. I've found that a bracket welded on the inside lip of the mount and then directly on the torsion bar tube with 1/8 inch steel is incrementaly stiffer. This has worked on my car to the past 2 seasons using SmartRacing 27mm rear bars. The latest failure was the nut ripping through the sheet metal as you mentioned. Having thicker steel cut and fabricated to reinforce the area is the second improvement needed. If you have a talented welder and body guy he can do this and the SmartRacing part is not needed. I can give some pictures later tonight.

[gumba]

I've been using the Smart Racing mounts for 2 years no problems at all. This is with there 27mm sway bars. I would think it would be cheaper to buy theirs vs. trying to fabricate one as good as theirs.

[APKhaos]

Mike's experience almost exactly parallels mine, with 30mm Smart Racing rear bar.

I fabricated a 1/8" steel reinforcing plate which was welded onto the 'open' face of the stock bracket, and then triangulated up to the torsion bar tube. Bomb proof!

The first time around, the nuts ripped through the chintzy sheet metal. Once that was cut out and replaced with 1/8" plate, all was well.

Its a fairly simple job, but be very careful that the bottoms of the reinforced brackets are perfectly aligned. The bar should turn freely when fully torqued down - before the drop links are connected. If it is binding, you will have fatigue problems with the brackets sooner or later.

[1974carrera]

89911 I would definitely be interested in seeing the pics of what you did...thanks.

gumba Were you able to add the Smart Racing reinforcements to the mounts with the mounts in the car or did you add the reinforcements to new mounts and then weld the reinforced new mounts into the car? Were your mounts the original style without, or the newer improved style with the wishbone reinforcement? I'll post pics of the new improved mount and the old style mount tonight to clarify what I'm asking.

[89911]

Here are the pics. I happen to have a reasonably priced auto body guy that is talented with welding and can fab out anything imaginable in minutes. You are still going to have the SmartRacing bracket welded in addition to there price. These were taken prior to the reinforcement on the sway bar mounting surfaces.

[gumba]

When I bought my mounts Jerry Woods was welding them up and selling them as complete units, so I can't be of much help.

[1974carrera]

Here's 2 pics of a new anti roll bar (ARB) mount with the reinforcement and 1 pic of one on my car that is the original design without the reinforcement.







It's easy to see how the reinforcing plate prevents flex of the mount so it won't crack. The Smart Racing kit has barrel nuts that get welded on top of the existing 8mm nuts, and a shaped metal plate that is welded to the barrel nuts and the mount (see the pics at http://www.smartracingproducts.com/ under 911 suspension). This serves to reinforce the mount just like in the new design mount and has the added benefit of the nuts being tied into the structure so they won't rip out. I may try to add this to my existing mounts since it seems like a good solution and if I do it now while mine are still intact I shouldn't run into any alignment issues. The triangulation and reinforcing plates that you guys have fabbed up seem like a good idea too, so maybe that's the way to go. Once I do one or the other I'll post some pics since it seems like many 911's must need this but there's not a lot in the archives on it.

Any other good solutions out there?

[89911]

If we have to do all this reinforcing and strengthening, isn't that telling us the intial design is flawed! The best solution would be someone to mill one out of solid metal! No reinforcements needed. Just tap a die into the solid metal block for the sway bar threads and its no going anywhere.

[1974carrera]

I think you're right 89911 about a solid mount being durable. What would be really convenient though, and what I'm trying to do, is reinforce the existing mount and avoid the hassle of cutting them out of the chassis only to have to align and weld in replacement mounts. I think you're right about the original design not being adequate and it seems like reinforcement or replacement is something that most every 911 needs or will need.