DS Rear Suspension
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Thread: DS Rear Suspension

  1. #1
    Fellow Frogger! Errol_S's Avatar
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    Default DS Rear Suspension

    I have read with interest the posts related to the rear suspension sinking rather fast, whilst the front does not. I too am experiencing this with my '72 DS20. The rear will be down within 30 minutes whilst the front takes hours.

    I have replaced the rear height corrector and suspension cylinders with remanufactured items from Citrotech, so that should all be good. I then did the suggested test of allowing the car to roll, and with the engine off step on the brake. The back did not sink. I do not understand why the car needed to be rolling, but I did as suggested. By 'passing' this test does it mean there is no LHM return via the brake control unit? I am considering changing this but am hoping to get some clarity that this is the cause before doing so.

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    The suspension works fine, but this sinking is bugging me and I must find out why?

    Any suggestions or further tests?

    Cheers
    E

  2. #2
    Fellow Frogger! Rally's Avatar
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    The rear sinking faster then the front is because of leakage through the brake control valve. The brake control valve is fed from the rear suspension circuit and as it has no rubber seals , just metal on metal so there is always a slow seepage of fluid. The BX came with an anti sink valve to solve this problem.
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  3. #3
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    Quote Originally Posted by Rally View Post
    The rear sinking faster then the front is because of leakage through the brake control valve. The brake control valve is fed from the rear suspension circuit and as it has no rubber seals , just metal on metal so there is always a slow seepage of fluid. The BX came with an anti sink valve to solve this problem.
    I do understand that something can get under the skin and just irritate, but how much of a problem is this really? Does the leakage through the brake control valve indicate excessive wear and does it affect brake or suspension performance?
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    Fellow Frogger! Rally's Avatar
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    There is so little fluid lost through the sinking is minor and there is no loss of brake or suspension performance. The anti sink valve on the BX was all about appearance , the boss thought that cars with the rear down looked ugly.
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  5. #5
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    Thanks - I was kind of thinking it was more about appearance than functionality. Me? i like every single quirky thing about a DS. I like the way the rear rises first and then the nose. i wouldn't have it any other way
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  6. #6
    1000+ Posts Ken W's Avatar
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    None of my BXes had an antisink valve. Bums go down quite quickly these days. However the Xantias with the 6+2 pump did get antisink valves because they take so long to come up with only 2 pistons pushing HP LHM into the suspension. The 6 piston bit was only for the power steering. They work well on the back where they have their own sphere to help the process.

    Cheers, Ken

  7. #7
    Fellow Frogger! Errol_S's Avatar
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    As mentioned everything functions well, but I have to agree with the 'The Boss' - it looks stupid having a low back end and high front. Obviously everyone is entitled to their opinion. But I am still none the wiser whether replacing the brake control will resolve the issue, considering the current one 'passed' the test mentioned above.

    Cheers

  8. #8
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    Default DS Rear Suspension

    A new brake control valve will stop the rear sinking as fast. That is assuming itís in better shape than the one on the car. Itís also possible there is a leak at one of the 6 or so pipe joints in the rear suspension / brake lines. Could also be the brake force distribution piston leaking as this is directly tied to the rear suspension pipework.

  9. #9
    Fellow Frogger! Errol_S's Avatar
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    An update. I decided to replace both the brake control valve and distribution piston with refurbished units from Citrotech. Now the suspension only starts to sink hours after switch off. In fact after 24 hours it has only dropped 1.5 cms. Of course this is dependant on the condition of the height correctors and suspension cylinders.

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