Upper Rear Shock Mounts - Broke 'em both

[BackinBlackS550]

I had an unplanned but really exciting agricultural side trip at Road America yesterday (exiting the Carousel, for those of you familiar). I broke the center out of both of my upper rear shock mounts and there are none available anywhere in the country that I can find yet. Someone in MI has 12 but they won't ship them out of state.

I have two questions.

1) Any leads on where I might be able to get a couple?

2) I thought about having someone fab a pair. It looks like it would be a fairly simple thing but I'm not a fabricator. Any ideas on where I could get this done?

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[DickR]

No help on your questions but do you know if they broke as a result of hard impact after going off course versus broke first which caused the off course? Any other damage since it sounds like one or more very hard impacts? Stock rear shocks and spring versus lowered or rear coil overs?

 

[Anthony@HTM]

Let the speculating begin....

 

[DickR]

Better to have facts first since lots of possible contributing factors and/or "what broke first" questions. From his signature block it looks like a completely oem suspension which depending on how he went off course might have been subjected to extreme impact or bending loads. Far too little info at this point since he was focused on getting the car back on the road. :-)

Edit to add pictures for those folks who haven't seen the mount and mounting location up close.

 

[BackinBlackS550]

I'm pretty certain the shock mounts did not break prior to going off the track, but the thought did cross my mind. I actually have a number of suspension mods but I also don't think they contributed.

My rear suspension mods are: Steeda springs and sway bars, Steeda billet vertical link, Steeda IRS bushing kit, Steeda subframe brace and Viking Crusader shocks. I have the sway bar set to the middle setting and the shocks are C=3 and R=6.

The car handles incredibly well and the two instructors that rode with me (one Porsche guy and the other an M3 guy) were raving about the car in general and particularly the sound and the handling. The Porsche guy called the car "wildly overpowered". Yeeha!

I may have located the mounts at Rock Auto, so if they arrive and I get them installed I will keep an eyeball on them. I still wouldn't mind finding someone to fab some really heavy duty ones.

 

[DickR]

Interesting. Thanks for the details . . . not that I have a clue what to "do" with them (not a mechanical engineer and not a Ford engineer involved with the loads and all those other variables).

Question: When you say the center broke did the shock rod "punch through" the center of the mount? Or did the center portion separate from one or more of the ears?

Also, when you went off track did the car get airborne and then land hard or do something like impact the rear wheels with something similar to a curb?

And (I'm just full of questions :-) ) did any other suspension parts break? How about the wheels?

Something to think about before installing a stronger upper mount: If it had not broken what else would have broken or bent?

Also, you might want to compare the bump travel of the Viking shocks and whatever bump rubber you used with the oem shocks and bump rubbers. If the Viking shock rod ran out of travel and bottomed "HARD" it would impact the upper mount.

 

[BMR Tech]

Sub'd

We've seen some failures with various pieces in testing, but not these yet.

Please post pictures when you can.

 

[BackinBlackS550]

The whole round center part that you can see in your second picture broke out. The rest of the mounts are still bolted to the car and don't look like they fractured. I haven't had a really good hard look at all the other components yet. At first inspection, the other stuff looked OK, so I drove the car home. The car got a little airborne but probably not more than a few inches. I went off onto the grass, but I was going at a pretty good clip.

 

[BackinBlackS550]

Sub'd

We've seen some failures with various pieces in testing, but not these yet.

Please post pictures when you can.

I'll take some pics in the next few days Kelly when I get it apart. You guys were one of the possibilities I thought of for making a part. I'm happy to be a Guinea pig if you want to give it a shot.

 

[DickR]

The whole round center part that you can see in your second picture broke out. The rest of the mounts are still bolted to the car and don't look like they fractured. I haven't had a really good hard look at all the other components yet. At first inspection, the other stuff looked OK, so I drove the car home. The car got a little airborne but probably not more than a few inches. I went off onto the grass, but I was going at a pretty good clip.

Hmmm. That is "consistent" with the shock rod bottoming internally. Did you use the oem bump rubbers which are actually progressive rate "springs" or did you use bump rubbers that came with the Steeda springs which also are probably rate "springs"?

Or did you use bump rubbers that came with the shocks?

The idea is that with the limited travel of modern suspensions, even with stiffer but shorter aftermarket springs, the progressive rate bump rubbers are necessary to prevent internal bottoming of the shock rod. Also if the Viking shock has less internal travel available even the appropriate bump rubbers might not be sufficient.

This is all reasonably educated "speculation" on my part to help you determine the actual root cause/solution.

 

[BackinBlackS550]

Hmmm. That is "consistent" with the shock rod bottoming internally. Did you use the oem bump rubbers which are actually progressive rate "springs" or did you use bump rubbers that came with the Steeda springs which also are probably rate "springs"?

Or did you use bump rubbers that came with the shocks?

The idea is that with the limited travel of modern suspensions, even with stiffer but shorter aftermarket springs, the progressive rate bump rubbers are necessary to prevent internal bottoming of the shock rod. Also if the Viking shock has less internal travel available even the appropriate bump rubbers might not be sufficient.

This is all reasonably educated "speculation" on my part to help you determine the actual root cause/solution.

The Vikings don't come with bump rubbers and they say they are not necessary. The other thing that happened is the wheel well liners were ripped out, so maybe it did bottom. But even still there is so much travel available in the shocks that I can't see them bottoming out.

 

[DickR]

When you get the shocks out of the car you might check to see if they compress normally and/or look damaged. Something pushed the center of the upper mount. Maybe the bump/compression resistance of the shocks themselves is high enough but that is a lot of bump resistance I suspect (but don't know since I'm also not a shock engineer :-) ).

 

[Daytona Coupe]

This adds to my fear of going with rear coilovers. That mount looked we to me before, now I'm really suspicious...

 

[Anthony@HTM]

No bump stops and bottoming out hard would do some damage.

 

[MtnBiker]

This adds to my fear of going with rear coilovers. That mount looked we to me before, now I'm really suspicious...

I put Vikings on my GT and after playing around with the rear mount I'd say coilovers make no sense. The mount seems pretty week to me - the integral bushing takes up some of that thickness on the mount so the metal is kind of thin. The failure isn't all that surprising to me. I too would consider a more robust design as long as the intent wasn't to have a sacrificial upper mount vs a broken control arm.

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