CQ/S2 top mounts.

[macspring]

how the standard bush is actually very good in dampening shock and road noise compared to poly bush?

I'd agree with the above, i.e. that one get a much nicer ride from a fresh oem top mount rather than the 'crashing' of a poly bush - Potholes and bad road repairs cannot always be avoided when driving on the roads (as opposed to a track).

Having said that it has to be accepted that the oem top mounts will have to be changed more frequently, but imho it was worth it...........but it was one of the multitude of reasons I am happier to have switched to a C4 chassis.

[Lago Blue]

Ooops...

Hi John,

Thanks for that, I believe I've now fixed the link. With that article I hope that, rather than cast aspersions on poly bushes, I made clear that genuine near-stock (does Boge sound familiar?) can be really good and why some may prefer what that offers. Not unlike top-mounts, it is important to try to fully understand the total job description of the involved parts, the what, why and how of various failures and how they might be prevented.

One does have to be a bit pointy-eared to get the best out of these cars don't you find? But I was hoping no one would notice.

I did mention above a couple of times the author of almost all of this info and I have only made a very few changes/additions of my own. He is without doubt, the most widely acknowledged expert WRT all things Audi 90. Fortunately for us, he has also been a very generous author. All but one of those numbers were as a result of his experience and research into top-mount failures and fixes; and certainly we benefit from his extensive off and on track time and data gleaned from the shock/strut dyno and other strut-tower mock-up equipment he made to test mounts to various kinds of failure got him the particular numbers; and numerous possible fixes. With that background, in the course of his manufacture of Mount-Savers and Pro-Mounts, he bought and dissected so many Boge mounts that eventually he was able to determine how many factory die-sets they had involved in all their mount's production.

[Vorsprung durch Technik]

Hi John,

One does have to be a bit pointy-eared to get the best out of these cars don't you find? But I was hoping no one would notice.

Pointy eared or not.......... Lago Blue,it' very much appreciated! I'll get that measurement you ask for later tonight hopefully.

[Audicted]

Pointy eared or not.......... Lago Blue,it' very much appreciated!

[Lago Blue]

Why Bother to Replace Worn Strut Top-Mounts?

It's a Well Known Issue:
As was mentioned above, many experienced owners recognize that when just replaced, almost any new mounts (the reco'd Boge included) briefly feel absolutely great but even the best, despite several revisions; still fail. Some accept this rapid decline as just the cost of doing business, however neither does it surprise me to hear that folks have left model 80's and 90's behind altogether, because of issues including this persistent Achilles' heel. Un-aided, even the best OEM top-mounts are inescapably perishable, even if they go slowly enough that you don't notice till they are truly rattling. So like tires and windshield washer fluid, they need both monitoring and periodic replacement. Similarly, on any given day you might totally consume whatever you have left of yours.

It's a B-Series Audi Owner Tradition to Moan about Mounts:
Its an exclusive club. Membership has its privileges. Just kidding, almost.

It's a Protection Money Racket:
Once mounts are leaving the 'in service" range and collapsing into the "failure" range, they simply offer increasingly less service and protection to the chassis. Left alone, each subsequent impact further weakens (and hastens the decline in), what impact resistance remains, increasing the chance a large ka-POW might crack your fender-turret.

It's an Annual Rite of Spring:
When the worst of winter has been weathered, and the promise of spring is yet just that, a middle-aged man's fancy turns to, well pretty much any excuse to spend hours in the still freezing garage and tear the old barge apart; again right? Top-mounts, the perennial favourite first item on that list of excuses, could it perhaps be permanently struck-off the list?
Or words to that effect. That surely isn't possible, is it?

It's a Preventative Maintenance Choice:
Experienced hands will know it is just less stressful to replace them before you absolutely have to. However, just like knowing how deep the next pot-hole is, correctly judging how far you can defer the inevitable may be difficult. A prudent maintenance plan would schedule their replacement during some neighbouring and dependent equipment change-out (at seasonal tire change, say) and/or service (such as during your pre-realignment checks to ensure all is rack-ready). Better control of tire wear is the logical outcome of an a proper alignment that, with mounts kept "as new"; better stays that way.

It's a Driving Response Quality Critical Item:
Metal-lastic joints such as these are the connective tissue of the chassis. Keeping them -all- in good order makes the car just so much more pleasant to drive. Less NVH, better straight-line and braking stability and better steering response are some of the day to day benefits. Frankly, IMHO perhaps one of the best features of my car is its' steering feel. I don't think that overall, my near-stock car is particularly extraordinary, except for its steering.

It's almost a Political Choice, the Status Quo (Dealer part, dealer price) or Something's Got to Change (Anything but the dealer!):
There are alternatives to simple stock replacement, this is but one. Below are the two main reasons why I think this one works.

a) It's a Core Integrity Issue:
Being that in the stock installation, the OEM part's rubber core and bonded interfaces are, un-aided immediately vulnerable to being forced to over-extend axially (and here, vertically), which will mark them for more rapid collapse, a best fix will be obtained with a mount core thus restrained from new. Held (by the use of a "Strut-Stop" mount aid) within its elastic limit, rather than increasingly ever weaker to inputs towards failure, the mount then exhibits only progressively more resistance to displacement as the new reduced available travel distance reaches a now fixed maximum soft limit; and may last indefinitely. In effect we can tighten & toughen the mount before use to prevent said damage. The mount maintains an acceptable level of compliance, its' installed height, its' critical "as new" bonded interfaces, has an increased peak load capacity, it keeps the bearing cushioned, and just continues to bounce back undiminished by years of use; &

b) It's a Co-dependency Issue:
This contends that to really make an overall tangible improvement to the driving quality of the car (in my view, a higher purpose than simply fixing the top-mount), one must not ignore that the fixture-ing (sp?) of the other end of the Mac. strut, suffers similarly; and deserves the same attention as the unfortunate usual focus on just the more obvious top-mounts.

The technical explanation for this circumstance, is two-fold:
1) To really strengthen the ability of the strut to best transmit normal driving loads (think cornering and braking) to the chassis, the three main attachment points of each wheel's suspension must contain as little uncontrolled free play as possible; &
2) To really refine the steering, imprecision in steering related suspension joints must also be eradicated. Of all the locations where slack exists in the whole steering linkage train; where intended motion is lost to slack joints, or unintended motion is allowed to occur, the most over-looked is the (lack of rigidity in the bare OEM arrangement) with which the Mac. strut is held steady. The play you -will- find in the used un-aided OEM A-arm bushes (and top-mounts) must be removed in order to :

a) Better fix the alignment geometry (by giving each attachment point a strong sprung-to home position);
b) Better transmit only true steering signal, both to and from the driver (by improving the very connectivity of the steering linkage); &
c) More precisely link together, an axle's two wheels' steering (by forcing each to more closely trace their own unique design paths, such that they better agree and compliment one-anothers' intent, which despite opposing positions, allows them both to also better mirror each-others' design purpose).

As the strut axis acts as a fulcrum between the tire's contact patch and the steering rack, any slop in the struts' fixturing, top or bottom, has to be taken up and will be (and somewhat randomly, depending what else the car is experiencing at a given moment), with every lateral linkage-loading before true steering "signal" can get through the "noise" of lost motion; due to said slack in the train. As it takes 3 fixed points (on the chassis) to only then properly suspend a 4th point (the wheel-hub) in space, even given an LBJ in perfect shape (whom usually consumes nearly all the attention, to the detriment of the A-arm's rubber mountings), three cores (two A-arm bushes; and one top-mount) in extremely good shape are still very much required, to most narrowly re-trace the Mac. strut's design arc of travel, to in turn best fix in place, the tire's contact patch relative to the chassis and the other tires, and;

d) Will go a long way to allow clear steering signals to be both sent and received; immediately and unaltered;
e) Kept in near perfect shape, are a vast improvement over how degraded an un-kept stock arrangement can easily become; &
f) Are necessary on each car corner (as applicable) to more deftly guide the aim of the tires' contact patches to most closely work together, to simultaneously act; as one.

The three bare stock OEM strut attachment bush and mount cores need to be extremely well bracketed and reinforced to best effect the above and to allow for the best transmission of clean "steering signal", and to minimize "steering noise" (i.e.: false signal). That is exactly what those aids (the Strut-Stops & Arm-Stops mods) do.

By more precisely fixing -both- ends of the Mac. strut, we cause it to more accurately hold and re-trace the theoretical design position and arc-path with each successive suspension load and movement. Further, whether or not it's length is changing or not; it is neither entirely rigidly attached nor loose or wandering at the top or bottom, but is quite stiffly held; and sprung to a fixed home position. By the removal of much of the randomness of the un-aided strut's ability to both hold position and move accurately through it's arc of travel, we add precision to the steering linkage train. A tangible improvement in the driving of the car should be the expected result of these small changes to remove lost motion from the steering.

In my case, the improved service life & steering response etc., is almost entirely because each of the 3 critical bits (the top-mount's core & the A-arm's two bushing cores) for each wheel, that locate the steering axis (the top & bottom of each Mac. strut), are in the best shape possible. All are stock OEM but "aided" by a Pro-Mount's spherical, Strut-Stops (an ersatz "Mount-Saver") & A-arm Stops that compared to stock, more firmly locate all those pivot-points by limiting those core's axial compliance. That more limited axial compliance is achieved by the aids' function, which is to bracket and reinforce those cores, by limiting their travel to a range that, by staying within their elastic limits, keeps the cores from self-destructing; for a very long time.

Those core's continued undiminished condition, as near to new as possible, is maintained primarily by said "Stops". The extended service life of those still un-torn cores and even that of the spherical, and the dynamic benefits nearly a decade on now, owe that excellent condition to those aids which simply reinforce the original design intent of those stock OEM parts.

Compared not just to the most often found worn stock condition, but after addressing all the other obvious possible areas of concern, that I now have effortless accuracy at my fingertips with which to guide the car, I am convinced of the value of these two mods which together, have provided more precise steering and maintained it longer term.

It's a Solvable Problem:
It just needs re-solving. I am fortunate to have bought both Mount-Savers & Pro-Mounts when they were available. They are both very good in their respective forms. In my view that approach is worth pursuing again precisely because in part it avoids some of the very issues others have mentioned here above. Many hands will make the work light. Presently some "Ersatz-Savers" are being independently tested by another forum member. Perhaps over the winter I can solicit some further help? Some of you may have seen this "Help Wanted" ad:

Wanted: Volunteers to test product to aid front strut-mounts.

LB

[Vorsprung durch Technik]

I'll get that measurement you ask for later tonight hopefully.

11mm at the passenger front ( UK ) being the originals and covered 75,000 miles from new.There is a slight knock sometimes from that side but nothing at all from the drivers side! The slight knock appears only when going over speed humps and not always, depending on speed, but then i drive it like a grandad around town only opening the taps on the motorway only.most years i only do 1,000 miles or less and thats virtually all motorway work.

[andy10v]

Mance posted the pressure required to collapse the mounts as just over 2000psi, meaning a sharp 3" bump/dip at 20 mph in a V6 B4, or if the suspension bottoms out. From that you can see why some people have mounts that last ages, and others will collapse them on the first drive, depending on road conditions and driving.

[Lago Blue]

Knock knock knocking on the garage door...

Vorsprung,

That can't be fun. Isn't the whole point of perhaps even today still one of the world's otherwise best handling station-wagens to at least hold steady all four contact patches with alacrity? Hey, we've all been there. One aim of the installed top-mount aid mentioned above is to then allow them to be forgotten.

Inherent Stability:
Something I've learned is that to go really fast comfortably, one has to travel in a straight line, which can be kind of boring. However, in order to have that bullet-train stability at speed which makes it seem effortless, I need to first have the most absolutely pin-sharp low-speed steering precision and response, which instead makes me want to take the long way home. In my view it is the low-speed driving which is the really fun stuff. The two mods mentioned above in this thread are a big part of that.

Lost Muscle Memory:
If you don't happen to drive the car often, you may not so readily notice the therefore less rapid decline in driving control response, however you will be pleasantly surprised after their replacement when all your mounts' function has been fully restored.

Fencing Axis Travel:
Understanding some of the many functions the OEM strut-mount has to do, and how only a still service-able resilient mount could do that; helps to explain the above now audible snag. As mentioned previously, consider that even at the best of times, there is literally a ton of weight bearing down on these two small front bushings. As well as being the conduit through which primary loads (vertical energy both for gravity and road impact loads) are transmitted through, between that chassis corner and its' tire's contact patch, they must also (to the extent they are able) steadfastly fix "still" the very tops of the two steering axis to the secondary loads (braking and cornering), and here's the key; together, as if they where one. Because the stock top-mounts ability to withstand these secondary loads is also rather modest, it again emphasizes the need to preserve the mount cores' new condition to also best resist them. By fencing the vertical axis travel available to the mount core, relative to its' shell, to a range below the point where internal damage occurs, the as-new mount strength and resilience remains undiminished and available for all successive loading. Relieved of being over-stretched physically, the mount service-life now extends forward markedly.

Wheel Walk:
One can also imagine how, with its' hidden internal rubber structure torn through typical vertical collapse, and perhaps further damage which may have split the internal metal mid-band (as was just mentioned how tis too easily done in the post above), that a mount may have difficulty in now laterally fixing the top of the strut. Braking, cornering and acceleration all attempt to displace the strut-top side-ways and further tear at the mount. Hence the vibration, even at low speed that you feel. If you where outside the car looking at that off-side wheel (what you would call it, correct?) while that "knock" was taking place, and the car was moving slowly enough, you may actually see the wheel walk (slightly back on the way up; forward on the way down; and then back to somewhere in between those two extremes) in relation to the wheel-well opening, as the car also goes over that bump. I once took a strut out of a car where the famous slotted-nut (or steel "bushing") was worn down to an hour-glass shape from knocking! Like a shopping cart on uneven ground, only one front wheel is really steering, the other is just following, wobbling along until that clearance is taken-up. I do believe that the large front weight bias on these cars tends to mask some front-end issues. This isn't were all the wheel-walk comes from on these cars, but if one side is knocking, you just know that only one wheel is leading; and that they are no longer acting together "as one".

Mount Function Co-Dependency:
As damage accumulates in the top-mounts (or any bushing for that matter), because input forces continue as before, that load then finds new (and newly over-stressed) remaining avenues to travel. Those next casualties here will be the A-arm bushes, with similar bad effect. For some serious bed-time reading on that score and more, see the "...Stops..." thread linked to, above.

Pleasant dreams.

[Vorsprung durch Technik]

Lago Blue, having rebuilt the whole suspension on my first V6 avant using all genuine Audi parts 9 years ago when all these parts could be bought for much less less than a kings ransome, i can attest the difference is night and day.These cars can and do drive very nice indeed!

[MGaz]

Quick question,.. Will V6 top mounts fit a type 85 CQ car ?

[Lago Blue]

"Will V6 top mounts fit a type 85 CQ car ?"....

Absolutely, like they were made for it, both at the front and rear. I think I fully understand what you are asking, but for the benefit of other possible readers, this will talk fit, function and a possible fix.

Know that I did see a post once that listed several of, just the different Audi P/Ns that this part has had through the years; and there were half a dozen or so. Each revision marks a technical upgrade and those changes include load capacity improvements to the rubber density, possibly the central bearing; and certainly to the mount's internal metal rings.

The simple truth of ordering the latest V6 Audi dealer-sourced genuine Boge top-mount is that that particular way of sourcing this item gets you the latest upgraded part, currently the unlisted 8A0 412 355A P/N, which is molded into the rubber body of the mount, along with the Audi rings and the Boge name.

And yes, using the above in an earlier (and lighter) car gets you an erstwhile factory "sport" version relative to the originals, if you follow me. This is exactly the opposite (and in my view the preferred) approach to this issue, where unfortunately, folks often inadvertently seek out the least capable mount in their quest for the lowest cost part that will physically fill this same hole, perhaps unaware of the less rapid performance decline and avoided/delayed costs; the strongest item offers.

Not that they ("355A"s) are indestructible either. Alone, they just take longer to fail, but that is precisely why the aid I keep pointing at to preserve them, only fits correctly and works properly with this most durable mount. It is the obvious starting point if best solving the failure issue is truly one's aim. However, beyond outright failure prevention, the combination of Boge 355As plus Strut-Stops harnesses that durability to simply respond better to through-puts, improving the driving experience, which is kind of the whole point of owning these particular cars, otherwise why not just surrender to the whole Google-mobile self-driving thing.

"Fit" is almost worth discussing on it's own, as it is key to mount "function".

Non-OEM External Shape.
Some replacements do not even possess the correct original external OEM shape or size necessary to properly "fix" the new part laterally in place in the fender's receiver, even before any internal core break-down has taken place, let alone not provide the same generous total exterior contact area that, mating perfectly with the inner fender's receiver cup, contributes tremendously to the mounts' ability to shed and disperse energy effectively; longer-term.

OEM External Shape.
Throughout all of this part's OEM revisions going back to the mid seventies, that even though the height was changed and several internal characteristics, the profile of the top section (the tapered portion which is "cupped" by the circular receiver welded inside the fender-well) has not changed.

Solid Mount as Anvil.
This is why attempts to mount a spherical bearing solidly here often fail more quickly than stock. The bearing is being beaten upon (from below) with a hammer the size of some significant multiple of the car's total weight. Without the broad tapered exterior of the resilient OEM mount, the concentration of force is such that alone, a spherical bearing race here is being peened open again in a kind of reverse manufacturing process that, as if resting on an bare anvil, it is ill equipped to resist. It is receiving its highest loading along its axis of connection (a.k.a.: axially, and in this case vertically), precisely where it is weakest. Further, because a solid mount body cannot absorb, delay, diffuse and disperse impact loads as broadly, quietly or effectively as an OEM, any bearing will therefore suffer more in such an unforgiving location. The original stock mount is perhaps never replaced because -just- the stock bearing alone has failed, as that result is secondary. The bearing fails after enough resilience has first been beaten out of the the rest of the stock mount.

Compliant Mount Necessity.
Despite that some others have said there's no need for any cushion above the main spring, I disagree. Our pretty cars are but fragile spot-welded boxes of thin material. One of the jobs the top-mount must do is protect everything above itself, the inner fender turret-top, your butt, the fillings in your teeth and everything in between. At it's core, this part is an energy filter and transfer device among whose function's here, one is to take huge vertical point impact loads; and always diffuse them harmlessly. It does this by spreading them out quickly, bending them slightly and dispersing them outwards through 360 degrees, sideways into the domed inner fender. Its good function is only possible due to its (relative to alternative non-OEM mounts seen fitted into the receiver cup in the inner fender) generous external contact area, volume, particular shape and resilient strength. The instantaneous peak force it must transmit is measured in tons, as in several. The tire and spring are by themselves incapable of the above extreme peak chassis impact load -dispersal- necessary (think pot-hole), but not always possible without the presence of the broad and resilient attachment that a fully serviceable (think near-new) OEM mount provides.

Mount Fix Fences Mount Function.
Briefly, that OEM mount function needs to be "fenced" correctly to best obtain the desired result, is evidenced by both its initial new good performance, followed too soon by its ordinary self-destruction. That failed mounts exhibit few external clues to said failure, save for loss of static height and the disappearance of the top cavity, we may therefore assume failure occurs internally, from below (and mount dissection confirms this). That vertical compliance loss in worn mounts is the strength characteristic which, as it is depleted, also consumes the mount's modest lateral resilience; and not vice versa, we must therefore limit or "fence" the mounts vertical travel; to best preserve new mount function both axially and radially. This is the primary purpose of "Strut-Stops".

Except in Germany perhaps, where they must have laws against them, there is no limit to pot-hole occurrence, or depth; which are the singularities which will kill any and all un-aided OEM mounts. However, for the brave and discerning, an aid for such is at hand.