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Thread: DS Dampers

  1. #1
    1000+ Posts pottsy's Avatar
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    Default DS Dampers

    Greetings brains trust.

    I've finally managed to get some time in the shed working on Moby Dick. He's been pining for some TLC for a while so I thought I'd put him up on stands and suss out a few of the things that've been annoying me.

    First up was the characteristic of the rear suspension. On bump it was soft enough, soaking up speed bumps in an acceptable DS fashion, but on rebound the back tended to squat indicating (to me at least) perhaps a stronger than needed rebound damper rate. Is my theory right or on the wrong track here?

    First thing was to remove the spheres and check them for charge. These were a set of reconditioned ones (by Pleiades) that I installed in early 2006. Fronts are down to 500psi and rears down to 300psi. Considering the amount of hard work these have done over time, I'm actually quite impressed.

    OK, they need re-gassing to bring back the magic carpet. Mea culpa, I simply haven't checked them since.

    The front ones are riveted spheres, while the back have removable dampers, so I thought I'd suss out the rear damping settings.

    Interestingly, they seem to be different side to side. Looking at the picture, the centre core seems to have 16 holes in one, and 14 holes with a bypass hole in the other. The damping plates are also an enigma. Firstly they seem to be completely flat, not domed by even the slightest bit, and they add up to 27 thou on the rebound and 25 thou on the bump side. This translates to 69 and 64 100ths of a mm.

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    By the diagrams posted on here previously, rebound should be 60 100ths of a mm and bump should be 50.

    So it seems that as far as damping strength is concerned, they are too hard, but the characteristic is different side to side because of the different cores.

    As it happens, I have another pair of dampers which have the cores with bypass holes and 14 vent, so I'll put in a matched pair of cores.

    I'm also looking at changing the plates to be a bit closer to the original saloon rear spec. Given the limited availability of the plates, I'll try first of all simply removing one each of the 9 thou plates ending in 41 bump and 46 rebound. (100ths of mm)

    While this is less than standard, it should still be damped but "magic carpet" like.

    Time will tell.

    Any input from the Gurus? Am I on the right track? Is the back of the car going to launch itself into space over the first speed bump? Will Clarence the wonder hampster reach the beleaguered garrison in time? These are all questions.

    (Answers in a plain brown wrapper left under a tree at full moon, or, alternatively, posted here.)

    Cheers, Pottsy

    DS Dampers-rear-dampers-found.jpg
    Buvito Ergo Sum!

    The Fleet:

    2018 C3 Shine ("Oscar" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1982 2CV6 ("Gaston") Seasoned traveller
    1975 GS Pallas ("GiSelle") Next project
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    Hi Pottsy,

    have a read here

    Sphere identification

    EDIT: OMG... I just looked at the piccie... no wonder it's weird, you have an early valve block there without the bypass hole by the looks of it .... (the one small hole is the bypass).

    seeya,
    Shane L.
    PS: You don't need to send them off to plaides just for a squirt of gas, Peter Deker is probably just around the corner and will do them for the less than the postage to QLD and back. infact if your ever in ballarat I could probably arrange to stick a squirt of gas into them too... for the cost of the gas (I don't have a bottle here at the moment).
    'Cit' homepage:
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    '63 ID19 http://www.aussiefrogs.com/forum/citro%EBn-forum/90325-best-project-car-you-have-ever-seen.html
    '72 DS21 ie 5spd pallas (last looked at ... about 15years ago)
    '78 GS1220 pallas
    '92 Range Rover Classic ... 5spd manual.

    Yay ... No Slugomatics


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  3. #3
    VIP Sponsor richo's Avatar
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    On first glance
    1. The damper valves are incorrect.
    The one with the by pass hole is correct.
    2. The shim arrangement is incorrect.
    3. There are no 7 or 9 thou shims, they simply didn't make them in that size.

    Best to read a factory manual which will provide an explanation.
    The thread to which Shane directed you will give you some of the required information.
    If Pleiades fitted those two dampers to the spheres I would be very much surprised.
    Hope this helps some.

    Unfortunately I'm indisposed for any online discourse. Ray, phone me if you would like me to talk you through what I can see here.

  4. #4
    BVH Roger Wilkinson's Avatar
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    A couple more points, Ray.

    1. Shims are 6, 8 and 12 thou.
    2. Valve bodies without a bypass hole need small diameter 3 thou shims, and these are not present in your photo.
    3. Only the earliest shims were domed, in my experience. Later shims seemed to have a single fold. After a lot of use they seem to flatten, as you have seen.
    4. Make sure the nuts are correct. The images in the thread Shane linked to will help with that.

    Roger

  5. #5
    1000+ Posts pottsy's Avatar
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    Thanks for the responses gents.

    I read Shane's post with great interest when it was all hot of the keyboard. I've got prints of all the charts that have been posted with figures scribbled all over them where I've needed to convert to thou (My micrometers are non metric)

    Shane, I have no intention of sending these spheres back to Pleiades for re-gassing. I'll get them done by Peter just as soon as (a) I have a free time slot and (b) it coincides with Peter's availability. I only mentioned Pleiades as this was where the spheres came from as a complete set of reconditioned (new diaphragms etc) spheres. I bought them from Nick at Cars of France who sold them to me in good faith.

    I can't complain about their servicability, they've stood up well to the rigours to which I've subjected them. I'm just a bit disappointed that the valving appears to be a bit slapdash. Not what I would have expected. (Oh, and they have gold Pleiades stickers on them too)

    I installed them in 2006 and have only removed them once before for checking.

    The valving is as they were supplied. I don't believe Nick would have fiddled or lead me astray.

    The valve discs are as measured with my micrometer (to within half a thou I suppose.) They're also flat as my Auntie Maud's chest, defintely not domed at all as far as I can measure.

    The valve bodies were indeed different. The bypass hole is 1.78 mm as measured by a firm sliding fit of a nail that happens to be the right size and measures 70 thou give or take a poofteenth. Interestingly, this is also the diameter of the bypass holes in the front spheres, which are riveted type and appear kosher, even down to the blue rings.

    So for now I've re-installed the spheres with the correct valve bodies (the ones with the bypass hole) and 18 thou (0.46 mm) of rebound damping and 16 thou (0.41mm) of bump damping. Once it's back on its wheels I'll see how it feels and if necessary revise them then.

    Richo, hope you'r not crook. If you are, then hot lemon and whisky (or whiskey depending on personal choice) is something I always find efficacious.

    Cheers, Pottsy
    Buvito Ergo Sum!

    The Fleet:

    2018 C3 Shine ("Oscar" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1982 2CV6 ("Gaston") Seasoned traveller
    1975 GS Pallas ("GiSelle") Next project
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

  6. #6
    1000+ Posts pottsy's Avatar
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    Quote Originally Posted by Roger Wilkinson View Post
    A couple more points, Ray.

    1. Shims are 6, 8 and 12 thou.
    2. Valve bodies without a bypass hole need small diameter 3 thou shims, and these are not present in your photo.
    3. Only the earliest shims were domed, in my experience. Later shims seemed to have a single fold. After a lot of use they seem to flatten, as you have seen.
    4. Make sure the nuts are correct. The images in the thread Shane linked to will help with that.

    Roger
    Thanks Roger, (and Richo)

    Hmmm. Maybe I'm not squeezing the anvil up far enough. I've checked the calibration of my micrometer against a 1 inch standard I have and it's spot on. As a turner and fitter I'd make a good communications specialist. I never did go to a tech school.

    I suspect my shims are 6 and 8 one then.

    In any case, I'll see how it works out. Rear spheres are not all that hard to change, even if "certain" Levistons seem to leave them in wrecks.
    Buvito Ergo Sum!

    The Fleet:

    2018 C3 Shine ("Oscar" Mrs P's)
    1974 D Special Manual Sedan ("Moby Dick")
    2006 C5 HDI Wagon Auto ("Mephistopheles")
    1982 2CV6 ("Gaston") Seasoned traveller
    1975 GS Pallas ("GiSelle") Next project
    And for Fun, 1968 Mini Deluxe ("The R & D'luxe" 1078cc, Grin Factor 100!)

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