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Long term stress-testing OEM strut mounts by manufacturer...

Old 02-24-2006, 07:41 AM
  #1  
VAP
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Default Long term stress-testing OEM strut mounts by manufacturer...

<center><img src="http://pictureposter.audiworld.com/711/stresstest1.jpg"></center><p>
Some of you will remember over a year ago when I tested strut mounts for "resistance" to compressing. At that point the then-new Meyle heavy duty unit was the clear winner while the Boge (real Audi part# 8A0 412 355 A and stamped on the part) was runner up. Other strut mounts tested at the time were Lemforder and Cortico.

This time I wanted to test various OEM strut mounts for long-term stress, ie: how long could they remain fully compressed via hyper-extending the inner half under a 5,000lb+ load for extended periods without shearing/separating the two halves causing the inner half to tear away from its outer half and remain tight against the upper strut tower under-side. A point from which it could never recover.

This stress testing was needed as baseline data for designing the new OEM strut mount reinforcing inserts. I knew if I wanted to make these I wanted them to be augmented/enhanced by also being able to recommend the most resilient, durable and longest-lived strut mount rather than the one most resistant to a "single" compression stroke. Most resistance means little if it fails quicker.

To that end I tested the 3 remaining sets of strut mounts I had lying around, ie; Boge (Audi), Cortico (WorldPac)and Meyle HD (Ubernugen). My Lemforder strut mounts I tested last year are "MIA" but they too are "sometimes" a WorldPac item. All are "seasoned" by being purchased at the same time and over a year old and used in previous resistance testing.

Pic is of tools used to accomplish the test:

1. Dake 10,000lb arbor press

2. Audi B3 strut tower (cut out of car)

3. Machined arbor for pressing where bearing sits

4. OEM mounts (Cortico front/Boge rear/Meyle HD is on shelf to left)

Testing consisted of compressing mounts to over 5,000lbs. Enough weight to fully compress the mounts and force them to flatten against the under-side of the strut tower and equivalent to a medium shock load such as when encountering an speed bump/pothole without slowing down and bouncing of the struts internal or eternal bump-stops then freezing that position in time over an extended amount of time.

Each mount (except Lemforder) was then placed on the press, in its strut tower mating surface and the press handle pulled down WAY beyond full mount compression then locked in place.

Mount inspections were to occur at 24, 48, 96 and 120 hour intervals.

Meyle HD: Failed within 24 hours but I have no clue at what point within that time. Complete inner/outer mount body separation.

Cortico: Failed within 48 hours (other details as above).

CRP/Continental shredded upon compression. Didnt even allow me to walk away from the press before catastrophic failure... TWICE!!

Boge: Passed 24 hour test, then 48 hours, then 96 hours and even 120 hours. After removing from press post-120hour compression test there was zero sign of any inner/outer separation. Inner half had moved upwards .120" (under 1/8") immediately after removing from press and backed down .040" 24 hours later where it remains today.

To verify/confirm results and eliminate any flukes all testing was done a 2nd time on the 2nd mount of the pair. Results were not only "close" they were IDENTICAL!

Given the above info I'm definately convinced all mounts are not created equal and that we may be doing ourselves a disservice buying the cheapest mounts money can buy.

I find it very compelling that the across-the-counter Audi strut mount simply KILLS all other contenders. But I'm not surprised as I also found that to be true of Audi air filters flow-testing when I did that comparo against Mann, Mahle, Purolator etc several years back.

And I have no stake in this. I dont sell OEM mounts but I'm no longer convinced that because I buy a $12 mount that I've definately bought the best, longest lived or even a very good replacement OEM strut mount.
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Old 02-24-2006, 07:44 AM
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Default Pic 2: Strut mount set up in inverted strut tower and ready for compression...

<center><img src="http://pictureposter.audiworld.com/711/stresstest2.jpg"></center><p>
you can see how high the "relaxed" mount bottom is out of its strut tower seat in this pic.
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Old 02-24-2006, 07:46 AM
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Default Pic 3: Strut mount at over 5,000lbs compression...

<center><img src="http://pictureposter.audiworld.com/711/stresstest3.jpg"></center><p>
In this pic you can see the portion that was out of the strut tower seat is now compressed to below the strut tower seat.

This is what all tested mounts were subjected to.
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Old 02-24-2006, 10:12 AM
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Default

So why would Meyle be the best a ayear ago and worst now?
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Old 02-24-2006, 10:15 AM
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Default Also...you are testing them under load in linear fashion...

Would it make a difference if you had means of replicating constant suspension movement (up/down but also turning of the steering wheel)? Would this gain much different results? And what about strut mounts not sitting flush/level with the strut tower when steering wheel is turned and thus exerting all the force on only one side/edge of the mount? ...just some thoughts here.
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Old 02-24-2006, 10:19 AM
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Default yes, as thats the "only" direction the mounts see (linear-compressive)...

the bearing is only there to allow a friction-free spin but the struts, springs, mounts, hubs, control arms et all can "only" compress linearly and no other direction.

No sense testing in any direction these mounts are never subjected to.
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Old 02-24-2006, 10:20 AM
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Default did you even bother "reading" the post? The answer is CLEARLY explained...

in the VERY FIRST sentence of the post!
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Old 02-24-2006, 10:25 AM
  #8  
520
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Default Ummm...yes....what am I missing?

"At that point the then-new Meyle heavy duty unit was the clear winner "

The only thing I may have missed is you said originally tested for "resistance" to compression and now for long term compression - I guess that's it.
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Old 02-24-2006, 10:29 AM
  #9  
520
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Default Hmmm...I could of swear that when I had my OEM's in there...

and when wheels were turned while car was parked the strut cap would tilt on one side(depending which way wheels were pointing).

I understand the strut itself doesn't have much room to move around and adjust camber or castor when everything is tight but why would this cap tilt like that then? Its sits tight against the mount, no? Confused a bit...
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Old 02-24-2006, 10:30 AM
  #10  
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Default Let me "cut/paste" it here for you...

&lt;&lt;Some of you will remember over a year ago when I tested strut mounts for "resistance" to compressing.&gt;&gt;

They Meyle HD has the highest resistance to compressing. Takes the most effort to compress fully (about 1800lbs). But once compressed starts to shear until complete inner/outer separation of the mount halves occurs sometime within 24 hours.

If you want the mount with highest resistance to fully compress the Meyle should be your first choice. If you want the 2nd highest compression mount with the hands-down longest life under compression you might opt for the Boge.

Given this new testing and in "my" opinion the Boge is the running away better, longer-lived mount.
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