Rear Shock Mount Failure

[JStang15]

So on my way home today I decided to take a different route I don't normally take to try to avoid some traffic. I ended up nailing a monster pothole that I didn't see in time. I immediately started hearing a loud rattle/banging from the rear whenever going over uneven road. Got the car home and found one of the rear shock mounts failed.
So my question is: is this likely the cause of the sound I heard, or is it more likely that there's damage elsewhere? I took a quick look over everything I knew to check and didn't see anything else wrong. I'm also running Pedders coilovers.

https://photos.app.goo.gl/6HaXzNFXuZ4XRqyE8

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[BmacIL]

So on my way home today I decided to take a different route I don't normally take to try to avoid some traffic. I ended up nailing a monster pothole that I didn't see in time. I immediately started hearing a loud rattle/banging from the rear whenever going over uneven road. Got the car home and found one of the rear shock mounts failed.
So my question is: is this likely the cause of the sound I heard, or is it more likely that there's damage elsewhere? I took a quick look over everything I knew to check and didn't see anything else wrong. I'm also running Pedders coilovers.

https://photos.app.goo.gl/6HaXzNFXuZ4XRqyE8

Yes this happens. The mount is designed to fail before the body & weld nuts in the event that travel is exceeded. How low are you running?

 

[JStang15]

Yes this happens. The mount is designed to fail before the body & weld nuts in the event that travel is exceeded. How low are you running?

Thanks - good to know. It's been a couple years since I lowered it but I think it's around 2 inches or so in the rear.

https://photos.app.goo.gl/XKZKxqXr4Kakzoc38

 

[moffetts]

in the event that travel is exceeded

Like what happens with the BMR shock mounts?

 

[BmacIL]

Like what happens with the BMR shock mounts?

If you're referring to the utter BS that's been spewed over FB over the last two days, no.

Lowered car + stronger than stock mounts + none/thin/very hard bumpstops + pothole = mount failure.

 

[moffetts]

I have no horse in that game; I have the steeda mounts. So far so good.

 

[MidwayJ]

If you're referring to the utter BS that's been spewed over FB over the last two days, no.

Lowered car + stronger than stock mounts + none/thin/very hard bumpstops + pothole = mount failure.

I saw a post in a FB group yesterday with a pic that supposedly was a shock mount that was ripped out from where it was mounted to the car. Is that what you are referring to?

 

[kent0464]

So on my way home today I decided to take a different route I don't normally take to try to avoid some traffic. I ended up nailing a monster pothole that I didn't see in time. I immediately started hearing a loud rattle/banging from the rear whenever going over uneven road. Got the car home and found one of the rear shock mounts failed.
So my question is: is this likely the cause of the sound I heard, or is it more likely that there's damage elsewhere? I took a quick look over everything I knew to check and didn't see anything else wrong. I'm also running Pedders coilovers.

https://photos.app.goo.gl/6HaXzNFXuZ4XRqyE8

I’m not very surprised that a mount failed, I’ve been testing different coil over set ups lately and there isn’t much to the rear OEM shock mounts. The top is held to the body by 2 bolts and the contact patch to the body is relatively narrow and horizontal, so a substantial hit to the tire (pothole) will cause the mount to rock and bolts will either snap or the mount itself will fail.
Add that to the low profile tires and high spring rates for lowered and pp cars, and it becomes an issue.

 

[BmacIL]

I saw a post in a FB group yesterday with a pic that supposedly was a shock mount that was ripped out from where it was mounted to the car. Is that what you are referring to?

Yes. Guy was running no bumpstops, is lowered, and hit a big pothole. No matter mount he was running, something was going to break. The other guy who piled on also had the same thing, but tried to backpedal and say it was different. There's picture proof he was running no bumpstops and his is an airbag car.

I'm happy my much stiffer than stock spring rates help with this, actually.

 

[shogun32]

The top is held to the body by 2 bolts and the contact patch to the body is relatively narrow and horizontal, so a substantial hit to the tire (pothole) will cause the mount to rock and bolts will either snap or the mount itself will fail.

Which begs the question, does Ford have an affirmative-action hiring practice of getting their mechanical engineers from Detroit-area high-school drop-outs?

 

[BmacIL]

Which begs the question, does Ford have an affirmative-action hiring practice of getting their mechanical engineers from Detroit-area high-school drop-outs?

The above is not how the mount works. And that's extremely racist. Well done.

The shock has almost no angular articulation through the normal range of travel, and the loads do not "rock" the mount. The stock mount isolator is troublesome because it introduces additional spring rate and prevents the damper from responding and controlling the inputs as fast as it is capable of, but it's not an inherently bad design. Ever heard of sacrificial failure? You WANT the mount casting to fail before the body fasteners/body structure fails. Upgrading your mount to Steeda, BMR, J&M, Vorshlag will all introduce the possibility of failing the body structure before the mount itself, but particularly so if your car is 1) lowered significantly 2) stock/near stock or lower than stock spring rates, and 3) does not have adequate shock travel and bump energy absorption.

 

[shogun32]

Ever heard of sacrificial failure? You WANT the mount casting to fail before the body fasteners/body structure fails.

Point taken.

 

[Norm Peterson]

Thanks - good to know. It's been a couple years since I lowered it but I think it's around 2 inches or so in the rear.

https://photos.app.goo.gl/XKZKxqXr4Kakzoc38

2" lower? No wonder.

Chances are you'd already introduced some fatigue damage from lots of less severe bumps and this last bump was bad enough to use up all of the remaining fatigue life in one final shot. I'd plan on replacing both shock mounts if I were you.


Norm

 

[Hotpart.com]

As said above the key to keep this from happening is to run a progressive bumpstop to keep the shock from bottoming internally.

 

[Niz55]

I will definitely need this upgrade in the near future when I do a complete overhaul on my suspension.

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