Poll: Rear Trailing Arm Mount Reinforcement

[duracellttu]

How many of you have reinforced the rear trailing arm 3 bolt mounting area? I wasn’t aware of this weakness when I was doing my subframe reinforcement several years ago. However, now that I have monoball RTABs and moving towards a stiffer rear spring setup, I’m wondering if I should address this.

If you have done this what solution did you use? I’ve seen people just weld the seam around that area, but have also see thick plates similar to the subframe plates.

[Jersey_M3]

I have done this during my reinforcement. It’s easy to wire wheel it down, weld a seam in a couple different spots and properly cover it back up. Just made sure you get all the seam sealer out of the joining points first or you’ll have some shitty welds.

[Obioban]

In 16 years, I've seen this failure happening twice. Monoball RTABs should decrease the load on the pocket. I wouldn't sweat it.

IMO this reinforcement is only as common as it is because it is a legit issue on the e36.

[ethan]

IMO this reinforcement is only as common as it is because it is a legit issue on the e36.

And of course that infamous vid of the failure on track.

[Obioban]

And of course that infamous vid of the failure on track.

That is one of the two times I've seen this fail :P

[duracellttu]

Thanks for the feedback. I’ll just continue to monitor the area and address if it starts to show sign of fatigue.

[AussieE46M3]

As others have said, It's a major issue on the E36 chassis however, the design for the E46 chassis is very different and doesn't need any plates despite what some companies say/sell.

I suspect braking torque is the biggest contributor to popping spot welds. The inner most bolt sits beyond any spot welds so it can pry on them and concentrate stress on their edge.

I've just stitch welded that edge as well as the back and front of the straight edges when I have performed reinforcements. Dug up an old pic from a 325ci I did a while back.

[George Hill]

I've seen a couple now starting to separate, nothing huge and small enough most people wouldn't notice it. But now that I've seen it it happen the pockets always get inspected.

And when I do a RACP reinforcement the pockets get stitch welded as part of that service.

[Apex_80]

That is one of the two times I've seen this fail :P

Twice is enough for me, especially when the failure mode is possibly a huge catapulting barrel roll. I'd rather just do a quick stitch weld and never think about it again.

[DESMDR3]

Twice is enough for me, especially when the failure mode is possibly a huge catapulting barrel roll. I'd rather just do a quick stitch weld and never think about it again.

Link to video?


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[ZHPizza]

Link to video?


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It ain't pretty

https://www.bimmerforums.com/forum/showthread.php?2346405-E46-Trailing-Arm-Pocket-failure-story

[DESMDR3]

It ain't pretty

https://www.bimmerforums.com/forum/s...-failure-story

Thx but the link in that thread seems broken I will have to take your word for it lol


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[ZHPizza]

Thx but the link in that thread seems broken I will have to take your word for it lol


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So it is! Here's the video

https://youtu.be/J4zPECASIrs

[DESMDR3]

So it is! Here's the video

https://youtu.be/J4zPECASIrs

Ouch thankfully the cage did its job


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