Top Mount installations compared

[Rusty]

I'm not sure if something is getting lost in translation here. The top nut does not hold the bearing into a promount, as the assembly clamps on the spherical bearing ball section and as a result, has enough clearance for the bearing to rotate. Thus, the bearing coming loose in the mount leaves the whole system open to movement alloved by this clearance and thus the bearing can become unseated and it is only the mass of the car that is holding the bearing in place and stopping it moving the clearance distance between cup and mount. This is due to the gap between the mount body and metal cup, which alloys the cup to sit at an angle to the mount during turning or suspension movement. If it is that this cup is supposed to tighten against the mount body or the strut tower, then it would bind during steering and strut movement and would negate the use of a spherical bearing. Either way, I would be interested in an explanation and perhaps a few pictures of the setup to illustrate.

[VAP]

Rusty-

We use the same mounts you do with the same part numbers. In fact my Sachs/Boge strut mounts that I use for Pro-Mounts come directly from Boge/Sachs Europe. The strut bearing (OEM or Pro-Mount) rests on the strut hydraulic rod below thus preventing "gravity" from causing it to suck south. The strut nut up top when torqued prevents the strut-mount body and bearing from being separated along with the weight of the car also "pushing" the strut-mount down on to the thrust/spherical bearing and hydraulic strut rod. But I only want to do this once so bear with me a few days. I'll do a mock setup and include pics of the assembly sitting on a Bilstein and show you side/top & underneath views of the assembly which once assembled can "only" be separated with a wrench, ratchet/socket or spanner.

Meanwhile, and until I can get that together, please join me for a little "Breakfast in America" (thank you Supertramp!).

[Sonic]

[Rusty]

Yummers

The strut nut up top when torqued prevents the strut-mount body and bearing from being separated along with the weight of the car also "pushing" the strut-mount down on to the thrust/spherical bearing and hydraulic strut rod.

This is the statement that I would like you to explain with diagrams / pictures etc. If the top mount nut presses the bearing into the body then it must press on the upper surface of the mount body, either directly or through a series of interferences from the strut tower upper face, when fixed in the normal operating position and if this was the case, then this would render the bearing useless, as it would be fully constrained and thus unable to rotate in any direction. Your kit contains a spacer to prevent the cup from hitting the mount or strut tower (I have seen this) and this gap is especially promionent when steering lock is applied. If there is a gap between the mount body and top cup, then movement can occur with a loose or detached bearing.

I look forward to seeing the explanation for this in due course.

[s2_wot]

VAP easy on the top mounts, they can't be good for you!

As I have purchased 4 x junk 034 top mounts and subsequently 4 x OEM mounts I want to get some mount saver II's. I can upgrade to the pro mounts at a later stage funds permitting.

If anybody else is interested in having a set in the near future kindly put your name on the list below. If it makes sense we could have a few sets shipped at the same time. Prices per axle set (ex european taxes and ex transport) are shown further up the thread.

1. S2_wot: 2 pairs of Mount Saver II's

[VAP]

Rusty-

Gotcha, now I know the "gap/space" you're referring to and yes, it does exist in both Boge/Sachs mounts as well as Pro-Mounts. In Pro-Mounts its exactly .100" but I have no way of knowing the "exact" gap measurement on an OEM mount as I no longer have any of the Audi slotted nuts around to do a mock-up. However, I would've made that clearance identical to the OEM setup if at all possible so I doubt there's much, if any difference... couple 'thousandths' if any.

Below is a pic of a Boge/Sachs mount just barely modified on its way to becoming a Pro-Mount. There's a few OEM "INA" thrust bearings stacked around the strut mount and the tool I use for bearing removal when I get a new delivery and have to remove the OEM thrust bearings and machine the mounts to accept the PTFE-lined spherical bearings.

The bearings come from Boge/Sachs and have been pressed into the underside of the strut-mounts. However, it only takes maybe 35-40psi of pressure to fully seat them. Once seated they can be removed with minimal effort. I just tested half a dozen or so and ALL bearings fell out at somewhere between 12 to 18 psi of effort. Easy enough for me to use the alloy tool in pic, dropped into the OEM strut-mount and push the bearing out with the heel of my hand on 98+% of ALL strut mounts received. When I get a new shipment of Boge/Sachs strut-mounts fully 10% or so of ALL strut mounts I order show up with the bearings separated from the strut mount in the box just from being jostled around in shipping! Great for me since these are just "throw-away" bearings anyway! Someimes I'll encounter a "stubborn" bearing that I can't push out by hand so I simply turn the strut mount over with the tool in place and lightly tap it once on my workbench. Never encountered one that was any tougher/more difficult than that to remove.

In testing these I conducted numerous trials where I would install them in cars with the spherical and thrust bearings "indexed" to both the strut-mount and the strut-mounts to the strut tower bores. Then inspect them 30, 60, 90 or 180 days later and see if anything had rotated/shifted. Mine have been installed over 5 years and neither have rotated, ie; that is to say the bearing has not rotated within the strut-mount nor has the strut-munt rotated within the strut tower. Yet my sphericals don't even use the Polyamide hot-glue I use for publicly sold units! Additionally, upon removal and close inspection under up-to 200X magnification I can find no evidence whatsoever that either the bearing or strut-mounts have moved from their originally assembled/installed and "clocked" locations. There's no wear or "smearing" in either the spherical beaaring top-side or the strut-mount underside that indicates rotational movement and no indication of them hammering against each other. Further I've never heard or otherwise detected any "knock" sound as if the bearing separated from the mount by that previously-mentioned .100" gap then the two came crashing back together which would obviously create a not-so-discreet knock if it were to occur.

My suspicion is the spring keeps the bearing and the strut-mount in their original "clocked-together" positions from under the stacked assembly while the chassis weight creates a corresponding force on the top of that assembly and that at no time, even when I've gotten airborne once or twice has that dreaded knock sound ever occured nor bearing or strut mount relocated themselves rotationally.

I'm thinking much the same effect as we can run coilovers here in the US without use of helper/tender springs yet our springs being short (only 6"-to-7" tall) will come off the upper spring perches during full suspension drop when raising the car on a chassis-lift. Yet it NEVER happens when driving the car, again even when getting all 4 tires/wheels off the ground! Magic maybe? Judging by the sound that spring makes when it snicks back into place over its upper spring perch when lowering the car back on its wheels... that's NOT a sound you could miss in the cockpit!

Anyway, above pic shows the male convex "divets" in the steel underside of the Boge/Sachs strut mounts. I've also highlighted the corresponding concave divets those dimples make in the "very" soft walls of the OEM thrust bearings. The bearings are pressed in so lightly it doesn't even scrape all the paint off of those convex divets! And the bearing walls are so soft you can "dent" the sides of them with nothing more than a coin in your hand!

In essence there's really NOTHING tenaciously/aggressively holding the OEM thrust bearings or my spherical bearings firmly to the strut-mount steel cups. Just 6 dimples in the OEM setup and a Polyamide hot-melt adhesive in the Pro-Mounts. Given that, there "has" to be some other dynamic at-play that prevents them from separating and/or hammering against each other and crashing out-loud every time they come back together after any separation. My suspicion is they never actually "separate" due to the previous mention of chassis-weight on top of the strut-mount and spring/strut tension on the bottom of the bearing. But if you have another, better explanation, I'm ALL ears!

Can still do the fully assembled strut at a later date but "maybe" this is sufficient since
an assembled strut assembly will still only have the identical detail points as this post.

[A80Avant]

ill try the mount savers II as well

1. S2_wot: 2 pairs of Mount Saver II's
2. A80avant: 1 pair of Mount saver II

[Lago Blue]

Re: possible "other dynamic at-play"

Excellent question Rusty! Perhaps the answer is something like this:

a.) Take-off: Despite that some OEM stut-mount bearings apparently fall out of their mounts during shipping, it may be that the reason you can't pull a bearing down and out of a stut-mount whilst installed and in use is because, after the strut-assembly is fully extended and continues to fall, the entire mount also falls free, out of the inner fender receiver, preventing any downward load on on the bearing, so even that small amount of OEM interference (or none!) between the bearing and the floor of the mount is sufficient because it never gets pulled (it can't be, there's nothing to pull against); and it's only requirement is, as VAP stated previously, to ease installation. Continued downward strut movement will engage the upper cupped (and cushioned!) washer (secured by the top-nut) on the painted top-side of the fender well opening;

b.) High altitude cruise: the bearing is supported from below on the damper shaft, and gravity keeps the mount on the bearing; &

c.) Landing: No one has made a steering alteration while air-borne after apogee and kept it altered through and past touch-down to clock the fallen strut-mounts back into their fender-receivers; and lived to write about it!

[4WheelDrifter]

It's good to see you here, Mance. I'm sorry to read of your health problems. I wish you a speedy recovery.

I have a set of your CCK's with Pro-Mounts which I bought a few years ago, but I am yet to install them. I currently have a set of KW V1's fitted, so I will be interested to feel the difference.
I feel it's a shame I had to con you to buy your products through a back door in the US, as I did not wish to deal with Mr Jones here in the UK. I don't know why you insisted on UK customers dealing with him, as I know it put a few people off buying your products. But from speaking with you via emails I was convinced you had done your R&D on your products, so was willing to take the risk in buying them knowing they would probably be without warranty.
It's good to know that they should not be cleaned or lubricated in any way. I just hope they are made well enough to hold up to our harsh winter conditions here in the UK.
In the past I have accepted the original top-mounts are a service item. At least they are cheap, and are very quick and easy to swap with short springs.

[VAP]

4WheelDrifter-

Thanks for the welcome and well wishes!

While I am sorry you were forced to back-door me on how you got my products there's no ill-will. I was in an "exclusive" agreement with a UK distributor and when I give my word its my bond. When I did that there were none of the issues that became prominent later. Hindsight is always 20/20... we win a few/we lose a few, life goes on.

Just forward me a clean high-res photo of the as-yet uninstalled pieces and I will see you get assigned "original ownership" of those products and their warranty.

As far as that previous relationship let me say it was a countryman of this forum several hundred years ago that also commented on an equally sad situation:

"A glooming peace this morning with it brings,
the sun for sorrow will not shew his head;
Go hence, to have more talk of these sad things,
for some shall be pardoned, and some punished."

[4WheelDrifter]

Thanks Mance. I know you are a man of your word, and I can fully understand that you now have the benefit of hindsight, like many others. I'm afraid those that had foresight were often prevented from warning others, so there were many more victims than there needed be.
But I have already received an official warning here on the subject, even though I have always kept my own opinions away from the public forum, so I will say no more on the subject.

I will gladly forward high resolution photos of the kit later in the week when I am home.

[VAP]

Rusty-

I can now tell you empirically why the OEM thrust bearings or the Pro-Mount spherical bearings will never separate from the strut-mount once installed. Sheesh this was so easy but due to the prescriptions I'm taking for pain due to my surgery I have zero conceptualization skills remaining.

The simplest explanation is due to coil spring "pre-load" and nothing else whatsoever! When you install an OEM strut mount or Pro-Mount on a strut assembly out of the car it takes 87lbs of effort to compress the spring far enough to fully seat the strut mount. All I had to do to confirm this was measure a spring length with a strut mount installed on an existing strut housing with upper perch then disassemble it, mount it in the computerized spring tester and compress it again to the same length as when mounted to an assembled strut assembly and check the rate, ie; 87psi.

That means no matter what happens, even if the strut mount and strut housing assembly were to fall completely completely out of its "nest" in the underside of the strut tower there would still be 87psi of spring tension firmly holding the OEM or spherical bearing firmly inside the strut mounts lower cup as long as the upper nut is still threaded on the strut hydraulic shaft's threads. That tension is the "minimum" it could ever be since its the "fully extended/uncompressed" number and would still be there even when the car is on a chassis lift with all 4 tires/wheels are hanging freely and off the ground. Further there is no dynamic you could induce or create with the strut mount when mounted to the strut assembly that would or could alter that short of different spring rates and/or lengths. It remains so with assembled strut assembly in or out of the car. Of course that spring tension increases progressively as more chassis weight is lowered on to the strut mounts but in no event short of something failing/breaking can it "ever" be less. Its the spring "pre-load" and nothing else that insures the strut mount and its bearing never separate in-use! As long as the strut mount is bolted to the strut assembly there's a "minimum" of 87psi of spring tension pre-load pushing the bearing against the strut mount lower steel cup at ALL times! Now add the weight of the chassis on top of the strut mounts and its over 1,000psi per corner holding the bearings in the front strut mounts when car is resting on its "compressed" suspension.

When I went to assemble this mock-up it became vulgarly obvious soon as I started to compress the spring so I could drop the strut mount on to the assembly what the secret was. But I wanted that empirical "pre-load" number from the spring-tester.

[Rusty]

I understand whay you say but still disagree with your statement that the top nut holds the bearing in place in the mount - there is no load path to permit this - the top nut holds the stack of components that are directly attached to the strut shaft in place but places no compressive effort from the top cap, through the strut tower and onto the mount body - there are gaps between each component. The body can still separate from the bearing and the 2mm or so gap that exists between the base of the cup and the body would allow the body to move by this amount relative to the bearing. As above, there is no load path holding the body in place; it is the action of the weight of the car that does this. The top nut exerts no retaining force between the bearing and the mount body as there is a gap between the top cup and the mount body, as well as to the strut tower - there has to be, otherwise the components would be bound solid by the interference with either of these items. Should the bearing and mount part ways, the only force holding the bearing in place is that of the weight of the car; spring pre-tension only works up to the point of the damper travel limit and also assumes that the damping effect does not slow the rate of rebound of the damper to a point where the top mount is no longer held in place by the action of the spring tension.

[Ross]

I think enough of us were caught up in the whole QC / CJ saga... as far as I'm concerned, hindsight is a wonderful thing and as much as warning were given by those in the know Stu etc. unfortunately the guy was a VERY good salesman. I'm always one for giving someone a second chance.. sadly, not so much much now.

Fortunately for us all this in the past and we've moved on. My OEM mounts have been on for a couple of years now, I'm definitely interested in sorting out replacements if any group-buy goes on. I'm also happy to receive & redistribute in the UK like I did with the SPM group buy. I'd probably go for the mount savers on the rear and ProMounts on the front, for the RS2 if that makes any difference...

Good to see someone putting time and effort into a first class product, ala Bainbridge and Rusty on here. These might be costly but seem like excellent value when you think they last 50k+

[A80Avant]

rs2 doesnt use top mounts at the rear Ross. you only need the front ones.