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  • #16
    image_70374.png

    Nuvo,

    You raise an obvious but still very good question as it may both raise others and help answer some. Here (above) is another of Mance's often unique, and instructive photos.

    Above photo's original purpose:
    Here he has cut the top off a North-American (i.e.: swaged-top) strut to illustrate how one might preclude strut-tube bell-ringing with the always swaged down to 50mm at their tops (small bore) North-American struts and the requisite small O.D. B6/B8 Bilstein clappers, by positioning a short length of hose at the strut base preventing same. This belt and suspenders approach (to a known North-American and perhaps possibly the European situation sometimes?) guarantees things will stay quiet least till the gland nut loosens.

    Also fairly visible is the dished strut-base detail common to everyone's struts and otherwise responsible for centering all smaller (for 50mm struts) dampers.

    Together with the photo of the two damper bases above, one can see how the vented type damper base can't "block the drain-hole", while the non-vented type base might. If the water was above the non-vented damper base and outside the yellow tube, how does it exit? It may be that the route down & out (to the drain-hole mod) for any water in un-vented yellow-bodied Bilsteins is only via the thread's slim inherent interface clearances between the damper's screwed-in base, shaft and yellow tube? If such is the case, it serves to emphasize the importance of ensuring the gland nut seals are kept in excellent shape, something a carefully installed gland nut, boots and perhaps less well understood, even an OEM style top-mount (which lets the big chrome top tube rotate with steering inputs and the rest of the strut, which will preclude rotational seal wear) all help ensure.

    Unable to upload photo to post at this time. Shrank and cropped the photo 10 x, still won't work!. OK, was able to upload a previously uploaded photo so, tried removing punctuation from file name of original target photo; and it worked!

    OK, I'll try again (below) to upload Skull's (previously un-up-load-able without corrupting the normal photo presentation format at post #15 up thread) photo here which shows a European type 80 B4 front small OD (50 mm) strut tube-top being measured.

    Skulls photo of a smaller OD 50mm Audi 80 B4 strut tube top.png
    Last edited by Lago Blue; 21 November 2022, 14:05.

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    • #17
      That's a very helpful picture and description. Can you give details of the "isolator" hose diameters please?

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      • #18
        Note again this is a known issue particularly in North America where swaged-down (to 50mm diameter at the top) front strut tubes are all one finds on the front of B3/B4 cars; and there is therefore a 1/4" gap all around the damper base inside at the bottom of the strut, where the strut tube ID is larger. In Europe, there is a good chance your front struts are 55mm OD like B3 rears.

        Know in advance that I tried this with some hose which was of the recommended size, but it proved to be too small of an ID by just a tiny fraction, but enough to make damper insertion impossible. So I kept the strut vertical and followed the steps in post #1 above; hose-lessly.

        In Europe you usually (but not always) get straight-walled 55mm OD struts and larger O.D. Bilsteins with much tighter (and pretty much self-centering) annular gaps between damper OD and strut ID, but if one was trying to fit some of those smaller O.D. dampers which are also seen in Europe, this kind of thing may work at the bottom, however the gland-nut you may get with those dampers might not fit the strut tube up top.

        Better than just the numbers (more fun anyway), you can read exactly what the man said here:

        "Sheesh guys, we REALLY oughtta be..."
        Last edited by Lago Blue; 14 October 2020, 15:48.

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        • #19
          Stupid question time Can I drill the bottom of the struts with the shocks in place?

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          • #20
            Originally posted by Rikki Kitto View Post
            Stupid question time Can I drill the bottom of the struts with the shocks in place?
            Not at all. Was gonna ask the same question as caps are seized and cannot get them out
            '93 Audi 100 Avant - R.I.P
            '92 Audi UrS4 Avant - SOLD
            '93 Audi UrS4 Avant LPG

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            • #21
              Hunker is correct, there are no stupid questions. See end of post #3 above, paragraph ends in "brave!".

              If it was me and I had to do it this way, I'd sleeve the drill bit to stop its' travel as the damper base is resting on the other side of that same domed strut-tube base you propose drilling through, with only a small gap -right- at the center. Review the photos up-thread and you'll see what I mean.
              Last edited by Lago Blue; 15 August 2018, 20:19.

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              • #22
                Many thanks using a stopper is a must then to be safe

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                • #23
                  Thread revival time, what symptoms would the suspension show if this issue was present any ideas?

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                  • #24
                    Rikki,

                    If you are referring to "frozen strut syndrome" and not "loose gland nut syndrome" or "misaligned damper in strut-tube syndrome", symptoms may include but are not limited to: you may notice the front end slides out sooner while cornering; you may perceive your regular commute becoming both less smooth and a lot noisier; you are becoming aware of your increasing intolerance to road imperfections and start driving to avoid seen and known bumps etc.; and when it is fully developed, you are able to push down with your foot on the bumper heavily and the suspension - will - not - compress. The last and most ominous symptom that -may- be seen before dis-assembly (but not always) is oil on the outside of the chrome shaft of the damper.
                    Last edited by Lago Blue; 12 April 2023, 22:04.

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                    • #25
                      Very full answer as always bud thanks very muchly, I have noticed in certain situations the suspension feels quite violent on rebound. Imagine going over a bump at speed and the spring feels as though it is bouncing rapidly and not being damped as it should car also feels a bit skitty in this situation i.e if cornering and going over a bump seems to slide a bit not hold true

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                      • #26
                        A recent post by RDs got me thinking I should just also mention here that although this thread content can obviously be applied to all the B2 / B3 & B4 chassis front struts, it may be less obvious to some newer owners that all the above techniques can also be applied to the B2 & B3 Q rear struts. Cheers.

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                        • #27
                          Some notes WRT observed (in myself also, at least initially, years ago) drain/vent-hole mod hesitancy...

                          To be fair, I understand the reluctance one may feel when contemplating incorporating this mod (drilling even small-ish holes in suspension components!), however I think it is important enough to repeat the warning here and consider that the alternative is to simply wait for the cost of the inevitable consequences, which have been detailed on almost any Audi forum one might choose, to surely occur at some point.

                          It may help to recognize that beyond the beauty of this mod in its' simplicity, ease of execution, low cost, invisibility, and official factory sanction, is that decades on, there is a total absence of any side-effects which might otherwise excuse its' non-adoption.

                          On the technical side, know that this much newer design (2012?) Universal Motorsport Strut offered by Bilstein, (with vent encircled in 1st screen-shot below, a close relative which shares much of the same internal construction as our B6 and B8 Bilstein damper inserts), makes I think, a compelling comparison, particularly WRT it's functionally identical damper's venting. That interior cavity's air has to go somewhere; and eventually come back...

                          As a stand-alone feature (as opposed to both the non and integrally vented damper-bases of our earlier (1980's?) and more pedestrian B6s' and 8s', compare to photo in post #15 of this thread), this welder-ready Bilstein/Mac Strut has installed in its' bottom end, a ''100 micron stainless steel breather vent located at the base of the strut housing" (my emphasis added since this model Uni-damper comes from Bilstein already with a bracket-free external strut housing (that also functions as the distinctive yellow lower-half of the B6/8s we know well) for you D-I-Y-Bracketeers!). This Mac. strut comes with the uber drain-hole mod.

                          That this vent feature is a separate component (encircled in 2nd and 3rd screen-shots of Bilstein's drwgs., below), and is of stainless-steel (which speaks to its' ability to withstand years of water through-put unhindered), and contains a 100 micron mesh filter, all point towards the Factory's deemed necessity of a fully functional 'floor-drain' as an absolute necessity, not unlike our own learned situation here. Should we doubt their more recent re-visit of this situation and their considered reasoning?

                          3rd and 4th-Last photos are from a Canadian vendor (Fraal Performance, no connection) who appears to follow Bilstein's lead here and incorporates that same breather vent in his strut-bodies for Bilstein's similar 50mm internals.

                          In conclusion, it boils down to this. The moat that separates the top-end Bilsteins from much else is wide. They are made with a separate high-pressure gas chamber to prevent the oil from cavitating and/or boiling. The oil is temperature resistant. The up-side-down mono-tube design is used to allow the largest piston OD possible in a given strut ID, and to therefore allow the greatest oil and gas volumes, which in turn help keep the temperature down and the service-life long. All this as dampers turn linear-motion into heat, and lots of it. Why this matters is because when your hot dampers cool they are also going to suck moisture in just with the ambient return air-flow, and that water-vapour will condense and gather in the cooled metal interior. This slow process accelerates as the seals in the strut's cap-nuts wear over time (Early Warning: the 2nd-last screen shot is one of the earliest mentions (from Audiworld.com's Original S Cars Forum) of this issue, (note that contrary to what is said here, freezing temps are not necessary for the damage to take place, note also the date (2008), it ain't no fluke that it keeps happening.

                          There are other earlier pointers to this same issue in forums now extinguished. (Note also the Uni-Struts' more flush seal design also in 3rd screen-shot is less likely to hold water droplets than the B6/8 cap-nut). There is no need to repeat your own experiment here. Give the possible water an exit, Bilstein's own struts do, yours should be no exception. Last photo, this is the contents which Bowie69 emptied out of one of his front struts, upon disassembly and removal of the stock damper, surely it evidences that over time, an amount of water significant enough to cause this; somehow, finds a way in.




                          Bilstein 46mm Uni MtrSprt Strut Screen Shot 2021-05-15 at 08.45.00 copy.png Bilstein Uni MtrSprt Strut and Dmpr X sectional drwg of Damper Base and Vent Filter Screen Shot 2021-05-15 at 09.02.45 copy.png Bilsteins 46mm Universal Struts Dimension Drwg Screen Shot 2021-05-15 at 13.00.51 copy.png Fraal 50mm strut 1 Screen Shot 2021-05-15 at 13.14.07.png Fraal 50mm strut 2 Screen Shot 2021-05-15 at 13.13.38.png Audiworld Original S Cars Forum post re Frozen Strut Syndrome Screen Shot 2021-05-15 at 13.35.49.png from Bowie69s front strut interior upon disassembly Screen Shot 2021-05-23 at 13.46.13.png
                          Last edited by Lago Blue; 23 May 2021, 20:04.

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                          • #28
                            Thats fascinating! I guess Bilstein know a thing or two about damping... Including 'damp' inside struts.

                            I had no problem adding a hole to the bottom of my strut when i did a swap to B6 dampers. I sprayed a very thin cavity wax into the strut to line what was bare metal inside. That should help protect just as it does in sill cavities.

                            They've been on the car 3 years now and still love the way they work. It seems the harder they work the better they seem, i think the limits of my bumpy cornering confidence is reached before the dampers are over worked.

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                            • #29
                              Ha! That's a good way to put it Steve, and your tenacious cavity wax suggestion is spot on. An ounce of prevention vs literally pounds of cure, and for just a few minutes work to remove very few grams of German steel. With so many other things needing re-visiting and our re$ources on these cars, with this; a slightly shorter list.

                              I have to agree that a) despite the civilized ride quality of the B8s, quite to my liking, I never feel like I've given them too much to do; and b) perhaps the preceding is to be expected because the car's ability certainly exceeds my own. In terms of what must be a slight excess of capacity and/or capability, it is interesting to me that these dampers apparently mesh so well with quite a range of stock springs, from those on the earlier and much lighter 4 cyl. B2 cars (1272cc and sub-1030kg) through to the B4 V6s (1430kg) and the RS2.

                              Not to get too far off topic but as this may be useful to others, on my B3 Q Coupe's Bilsteins is a set of yellow H&R springs which I read as actually meant for a type 89 Q, "mit Sportfahrwerk" so perhaps includes the 1BE 20Vs(?), but because they are a (only slightly, as I've shimmed all four springs' top and bottom ends, now made effectively taller with plastic spring/perch isolators) lowering spring (which I usually don't care for), so they are also a higher rate spring. They are perhaps pretty close to but most likely slightly higher than stock 7A Q Coupe rates, just not quite the height for a stock 7A Coupe Q (at least in North America where all Coupes are Quattro), that is to say the back end of the car now sits noticeably lower than an otherwise identical but still original Coupe Q, the front-end isolators coupled with 'Strut-Stops' brings me back up close to the stock height for brand new top-mounts. So my front geometry (in particular, the front A-arms' slight negative dihedral (see red line on drwg. below) which is most important to me, and the Coupe's shorter early-style A/R bar to A-arm S-links (unlike the drwg.'s B4 type links) are working in their optimal design ranges) are as original. So as sir Bowie69 reminded me in a recent post in his excellent Resurrection thread, I think I'm not too far off of Sir Colin Chapman's wise words "Lightly sprung, and heavily damped."

                              for my Coupe H&R Springs (yellow) J:V Quattro 89:1 VA and 89:2 Fz. HA mit Sportfahrwerk.png Audi B4 Front suspension drwg LH side looking forward from behind the tire showing downward slope of static A-arm position Screen Shot 2021-05-16 at 10.29.25 copy.png
                              Last edited by Lago Blue; 5 January 2022, 02:58.

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                              • #30
                                Here's two short published items, first an interview (screen-shot below) from Audi Tuner magazine #8 2015 with the same Bilstein UK After-market Manager Aaron Quilter whose e-mail response was mentioned in post #3 above. He explains his job, how they can modify and do test the yellow B6s and B8s and others for street or track success, his UrQ fascination, and he also briefly mentions how one might prioritize work on our cars, including the importance of the basics like replacing the suspension bushings, dear to my heart! Second item is a link to Total 911's visit at Bilstein UK to learn about a bit of company history, product development and availability.


                                1) from Audi Tuner magazine Issue 8 2015 interview with Bilstein UK Aftermarket Manager Screen Shot 2021-07-17 at 15.47.50.png



                                2) https://www.total911.com/bilstein-uk/

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