BMR Suspension's New S550 Rear Upper SHOCK MOUNTS: SM760 - Design Finalized!

[shogun32]

What I'm seeing in those pictures is fatigue cracking

What's the gauge of the sheet metal? My guess it's just sufficient for the sacrificial setup. So when the mount is changed to rigid, the probability of failure goes WAY up.

Is there a way to get behind the sheetmetal? Is that surface even usefully flat? If it's slightly curved, the mounts will rock with enough force applied. A brace on the back side to spread the load across as much material wouldn't be a bad idea. Think of a thick-wall cup (id > nutsert, od < channel width) that is placed over the end of the fastener and held against the sheet metal with another nut (or itself could be threaded).

There are 2 failure modes:
* boneheads with lowered cars and no bump stops which drive the full compression-stroke shock-load into the bracket. This one can be avoided easily.

* 2000lbs of car traveling upward after a bump where the shock is acting in rebound. While the magnitude of the force may not be very high (if the damping was high enough the wheel would come off the ground) the 3" lever arm will exacerbate any rocking moments.

There may be a 3rd, which is the force put into the bracket should the shock top-out.

McMaster has rod-end seals as well though the SRI price is better. https://www.mcmaster.com/4737t14

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[Roadway 5.0]

That is awesome. Any guess on what size nut is needed?

 

[aleccolin]

That is awesome. Any guess on what size nut is needed?

I believe the small studs are M5. My concern with just using those studs, other than the small size, is I have no idea what is on the back side. If they're just used for assembly there's no reason to make it a strong connection, might just be pushed into holes in the sheet metal which would explain the dab of sealant around the base. I don't think my borescope will fit through the lower holes to check, so I'm planning to just cut them off, drill it out, and use (steel) threaded rivet nuts instead. My nutsert tool will do up to an M8x1.25, which should be fine since it's just a backup anyway.

 

[Roadway 5.0]

I believe the small studs are M5. My concern with just using those studs, other than the small size, is I have no idea what is on the back side. If they're just used for assembly there's no reason to make it a strong connection, might just be pushed into holes in the sheet metal which would explain the dab of sealant around the base. I don't think my borescope will fit through the lower holes to check, so I'm planning to just cut them off, drill it out, and use (steel) threaded rivet nuts instead. My nutsert tool will do up to an M8x1.25, which should be fine since it's just a backup anyway.

Impressive stuff bud; looking forward to seeing your results.

 

[BmacIL]

I believe the small studs are M5. My concern with just using those studs, other than the small size, is I have no idea what is on the back side. If they're just used for assembly there's no reason to make it a strong connection, might just be pushed into holes in the sheet metal which would explain the dab of sealant around the base. I don't think my borescope will fit through the lower holes to check, so I'm planning to just cut them off, drill it out, and use (steel) threaded rivet nuts instead. My nutsert tool will do up to an M8x1.25, which should be fine since it's just a backup anyway.

I'm pretty sure those are just drawn arc studs or CD weld studs, so they are not anywhere near as strong as a projection weld stud. I think that's actually a pretty good plan to provide some robustness.

 

[shogun32]

so, is there no way to get access to the backside of that metal?

 

[fatbillybob]

Mustang newbie but fabricating welder here. For the tearing shock mount area on the car is there a reason you can't weld any steel shock mount like the BMR mount to the car? That would increase load distribution on the area but can the shock still easily be removed or do you have to remove the shock with mount then remove the mount? I have not played with this design. Another option is plate the car like we do for thin sections of BMW's and then bolt the mount.

Spring on shock coilovers will put a huge amount more force in this area that was never designed for. The OEM divorced spring will not yet there are a couple documented failures in divorced spring setups. Possible there were other factors like bad bumpstops or shock body length or mismatched spring length etc. Vorschlag was mentions several times and his coilovers are using massive spring rates in I'm guessing the 3.5hz range. I have not weighed the car or unsprung etc just estimated the math. Terry has not reported ripping out of this area and I suspect he is putting more load into this spot than anyone other than a wheel to wheel racer using Terry's setup and jumping curbs.

 

[S550Whipple15]

Sorry for delay replies.


Just clear up some stuff...

Daily driving Vikings are set to 3C 0R per Viking.
Bumpstop ls are being used cut to length as spec for my bmr lower springs. Also Viking and bmr both have stated my failure didn’t come from bumpstops. I asked if with the increase of travel with new mount should they revise the bump stop cut marking? Adding travel back to the system? No need for the cut? They stated that’s not the issue and to follow install instructions.

And yes on passenger side first failure I did hit a pot hole.. Heaven forbid a street car sees daily street usage!!! I’m sorry I can’t trailer the car to the track and do a few pulls then load her back up and go home.

I didn’t hit anything on driver side to cause failure cracking.

My biggest issue is BMR did work with me and they rushed a revision which imo clearly means hmm we may have created to much of a lever. New mount they sent are about 1/4-1/2 shorter and also inward more.


I’m not trying to “smear bmr” just simply explaining hey I’ve had this failure and it could’ve been very bad as when the passenger side failed my shock almost went into my rim spokes. I have several bmr components on my car and have always been a fan.

Some one posted about welding the mounts to the car. This is the route we are going as it seems to be safest and best option to make sure they stay put.

new mount vs old

 

[Red65]

Sorry for delay replies.


Just clear up some stuff...

Daily driving Vikings are set to 3C 0R per Viking.
Bumpstop ls are being used cut to length as spec for my bmr lower springs. Also Viking and bmr both have stated my failure didn’t come from bumpstops. I asked if with the increase of travel with new mount should they revise the bump stop cut marking? Adding travel back to the system? No need for the cut? They stated that’s not the issue and to follow install instructions.

And yes on passenger side first failure I did hit a pot hole.. Heaven forbid a street car sees daily street usage!!! I’m sorry I can’t trailer the car to the track and do a few pulls then load her back up and go home.

I didn’t hit anything on driver side to cause failure cracking.

My biggest issue is BMR did work with me and they rushed a revision which imo clearly means hmm we may have created to much of a lever. New mount they sent are about 1/4-1/2 shorter and also inward more.


I’m not trying to “smear bmr” just simply explaining hey I’ve had this failure and it could’ve been very bad as when the passenger side failed my shock almost went into my rim spokes. I have several bmr components on my car and have always been a fan.

Some one posted about welding the mounts to the car. This is the route we are going as it seems to be safest and best option to make sure they stay put.

new mount vs old

Glad to see BMR worked with you to figure out a solution. As much as R&D is done with companies producing car parts, a race track doesn't always tell the full story. Obviously reputable race tracks will have some rough spots and possibly really aggressive curbs in some cases, but usually never super harsh conditions such as pot holes. Im sure they will continue to test and add in variables that were not initially used.

I also gave some thought to welding in the brackets to spread the load bearing. Given they are done properly, simple tacks spaced around the perimeter should hold just fine and be super easy to remove with a small angled cutoff wheel if the bracket needs to be removed.

 

[BmacIL]

Glad to see BMR worked with you to figure out a solution. As much as R&D is done with companies producing car parts, a race track doesn't always tell the full story. Obviously reputable race tracks will have some rough spots and possibly really aggressive curbs in some cases, but usually never super harsh conditions such as pot holes. Im sure they will continue to test and add in variables that were not initially used.

I also gave some thought to welding in the brackets to spread the load bearing. Given they are done properly, simple tacks spaced around the perimeter should hold just fine and be super easy to remove with a small angled cutoff wheel if the bracket needs to be removed.

Official word from those who have no reason to spin/hide anything is that the change was made to allow guys with 20" wheels to still get some camber. It would still reduce the likelihood of a problem like the two that have happened, though.

I'll be asking for an update as I still have the original with the big washer, which will need to be the smaller one with 11" rear wheels.

 

[shogun32]

that is one mondo bracket and what 1/8" thick steel? Has anyone done the 'clay' (or layout blue) test to see what the contact is to the substrate? I think welding the bracket is a very good idea. Or for us with other solutions, applying a piece of 18 gauge after bashing the underlying, properly flat.

 

[GregO]

It would still reduce the likelihood of a problem like the two that have happened, though

"Two that have happened"

The topic of body threaded insert failure is limited to a total of (2) known failures with this style mount ?

 

[BmacIL]

"Two that have happened"

The topic of body threaded insert failure is limited to a total of (2) known failures with this style mount ?

Correct.

 

[S550Whipple15]

I’ve welded them on the car now can’t get you the measurements I believe it’s 1/8”-1/4” thick plates.

I’m so sick of some people in this forum.... sorry not sorry! I’m not bashing... I’m simply saying hey after 2-3 Months of running these I found this failure! Please check yours and I’m curious to see if more pop up as several people stated could happen. I’m betting we find a few more. Bmr has sold 800 or so of these... So yes 2 out of that isn’t high failure but as several people posted they haven’t installed or just started installing these...

I’m sorry that I’m frustrated that a newer product damaged my car. Talking with bmr and them even stating we might need to revise and change the location. Also talked about ride techs design, made me fell like they released a product with out a ton of testing etc. THIS IS MY OWN OPINION! After several emails and phone calls with bmr! I understand that modifying my car is my own risk but with revision to the plate it feels like they missed the ball and are putting cars at risk.. again MY OWN OPINION!

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