Heartbreak-broken rear shock mount

Bmachine

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I finally decided to bite the bullet and get started on this. For context, my car still had the original BOGE shocks but the right side had evidently broken and a really poor fix had been made by the previous owner. Since my rear window is out, I really wanted to take advantage of that and do a proper repair on that bad side but also do the same to the other at the same time. First thing to do was to remove the shocks and cut off the top of the tower. I started with the left side because 1) easier cutting access since I am right handed and 2) I wanted to send the good one to the machinist so he can build a replacement cap to the exact dimensions.

The horror side:
IMG_9177.jpg

After examining the removed good cap, a few things became evident. And most of them have been alluded to somewhere along this very long thread.

The design of this shock mount is not necessarily bad. But it clearly is the manufacturing that is the problem. Specifically, they added that washer at the top (presumably to reinforce that section which is under a lot of stress) but they only secured it with 6 tiny spot welds to the top of the tower. Not only is this weak but it creates 6 point from which spider cracks start to develop as illustrated on @autokunst pictures.

So looking at this good one, it seems pretty clear that, unless yours have actually broken off (as in my case), one could easily add enormous strength by simply seam welding all along the outer AND the inner edge of that washer. I think that, even if some tiny spider webs have started, this is a relatively straightforward non destructive preventative measure that would ensure peace of mind for many years.

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halboyles

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I took some measurements as requested earlier:
Thank you Bo for taking the time to include the measurements and detailed pics. Our '74 has both towers welded around the edge of the top washers and the passenger's side has six bolts for more reinforcement. This all happened on the first owner's watch so I don't know why the two towers were treated differently.

As a possible alternative to just welding the towers in their original configuration, I had worked on a rear tower reinforcement design for emergency or pre-emptive use based on Steve Hose's initial design:


I have a CNC facility ready to produce these. For anyone interested, the cost is about $180 shipped in the US and perhaps less if we have a dozen or more interested folks. Please post your interest on this thread to make it easier to keep track of requests.

I carry a set of these for my own protection, but also in case a fellow E9'r runs into tower trouble.
 

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Bmachine

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Thank you Bo for taking the time to include the measurements and detailed pics. Our '74 has both towers welded around the edge of the top washers and the passenger's side has six bolts for more reinforcement. This all happened on the first owner's watch so I don't know why the two towers were treated differently.

As a possible alternative to just welding the towers in their original configuration, I had worked on a rear tower reinforcement design for emergency or pre-emptive use based on Steve Hose's initial design:


I have a CNC facility ready to produce these. For anyone interested, the cost is about $180 shipped in the US and perhaps less if we have a dozen or more interested folks. Please post your interest on this thread to make it easier to keep track of requests.

I carry a set of these for my own protection, but also in case a fellow E9'r runs into tower trouble.
I did see that. Did you have a chance to test it? I am concerned about that inner wall thickness in those photos. It is difficult to insert the shocks and slide their bottom end onto the big M14 bolt as it is. I think anything that makes the inner diameter of the shock tower even smaller may create problems.
 

halboyles

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I have not had a chance to test the piece in place. When I get the coupe up on a lift for shocks replacement, I will check.
Since Steve used this same design on his tower replacements, I was assuming that there was sufficient clearance.
 

Bmachine

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I think the design is good. It’s just that the wall thickness should not be any more than the tower thickness (2.2mm) in my opinion
 

Stevehose

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I didn’t have any clearance issues. I compressed the shock, mounted it on the M14 bolt then released it up into the tower. The replacement piece is incredibly strong and provides much peace of mind w/Bilsteins.
 

boonies

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I have a CNC facility ready to produce these. For anyone interested, the cost is about $180 shipped in the US and perhaps less if we have a dozen or more interested folks. Please post your interest on this thread to make it easier to keep track of requests.

I carry a set of these for my own protection, but also in case a fellow E9'r runs into tower trouble.

Hal, I had to go back through the posts and I think your CNC solution is this one:

1654786518378.png

I am interested in purchasing a solution, but would really like to see the fitment in action before doing so.
 
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