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Ferrari 412 rear shock absorbers

Discussion in '365 GT4 2+2/400/412' started by ONSilver, May 2, 2019.

  1. ONSilver

    ONSilver Karting

    May 26, 2008
    135
    Oakville, Ontario
    Having searched what I could find, I remain a little confused and hope the forum might assist my understanding. Apologies in advance if it has been covered - I could not find it.

    I am told I need 4 new rear shock absorbers for my 1986 412. These are part number 117722, and all the usual parts sources we all use say they are NLA and unobtainium. KONI North America have also confirmed this, and appear unable to offer a solution. Several members have noted they switched to coil-overs (whatever they are) as the load-levelling versions are not available.

    I have found several shops in the US that say they can rebuild the old ones ( between 6 weeks to 4 months to do so). So that's one option. Any recommendations for any specific shops would be welcome.

    A second option is to switch to the coil-over type. Example: https://lbilimited.com/wp-content/uploads/2015/10/Suspension-Modification-Details.pdf

    And a third option is "apparently" to use new KONI shocks without the load-levelling feature - their part number 82-1825SP2. I am assuming these will be correct dimensions to fit the car, without using the plumbing in place? If the new KONI shock is the NON load-levelling type, what do you do about the oil lines and connectors plumbed for the original shock - remove?, cap and seal? etc?

    My question is which way to go? My understanding is that the "central" levelling cylinder (part #117737) was the "driver and controller" for the rear self-levelling - would this still be the case with the outer rear shocks switched to the non-levelling type? Will it function ok?

    Not a big consideration, but last, I would assume if the setup becomes non-original, there would be penalties for FCA concours judging!

    Apologies for the long post - would appreciate your suggestions! Thanks, Oliver
     
  2. samsaprunoff

    samsaprunoff F1 Rookie
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    Jun 8, 2004
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    Edmonton, AB Canada
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    Sam Saprunoff
  3. raemin

    raemin Karting

    Jan 16, 2007
    219
    Lyon (FR)
    Full Name:
    R. Emin
    The 412 des not use the same loadleveling unit as featured in the previous models. On the 400i gen 2 and 412 the system is a Citroën patented solution that was also used in Mercedes and RollsRoyce. Unlike the older system, this is not a self contained unit: so it rougly consists in 4 parts:
    1) A pump
    2) Two pressure accumulators (a.k.a "sphere")
    3) Two "Shocks"
    4) A sensor (see the lever that's under the spare wheel)

    This system is really nice and I would not replace it with coil-overs. Issues with these systems are either related to either the sensor being stuck by dirt, or a "flat" pressure accumulator. Some companies can refill the accumulators (with nitrogen?), but chances these are now porous beyond repair. They are similar to the accumulators used in the old Mercedes (500/560 SEC, SEL), except for the fittings. There are some reported success with Mercedes 500/560 accumulators. No idea if the pressure is correct, but as said some shops can empty/refill the accumulator.

    Please note that I have experience with the Mercedes M100, not the 412 or even the Mercedes 560, looking at my cousin's 412 I can say the system are indeed very similar, but I never personally swapped parts from one car to another. Getting in touch with a Citroën specialist is probably your best bet (as we did with the M100).
     
  4. raemin

    raemin Karting

    Jan 16, 2007
    219
    Lyon (FR)
    Full Name:
    R. Emin
    My Citroën mechanic is long gone, but here is a link to a company based in Paris which is dedicated to refurbishing these suspensions. "http://www.hydrosphere91.fr/lasphere.htm" with the corresponding prices "http://www.hydrosphere91.fr/tarifs/cx.htm". These prices are for mainstream Citroën cars, so one can assume that the price for a prancing horse will be more significant.

    A mechanic with RollsRoyce experience could probably be of some help. For a U.S based solution, maybe Karl Middelhauve would accept (?) to service the accumulators or provide hints on who could do it: he is a Mercedès M100 die-hard, so our suspensions do look pathetically simple compared to what he is used to...
     
  5. Italian Tuneup

    Rossa Subscribed

    Apr 16, 2019
    13
    Europe
    Full Name:
    Stefan
    Usually the shock absorbers itself are not the problem. They are not even shock absorbers in the proper sense. If they are not leaking and moving they are probably fine. All damping is done in the spheres or accumulators. I am pretty sure that every accumulator in every Ferrari 412 today is broken when not repaired.

    I had mine reproduced by a company in Germany. They checked if the old ones can be refilled but as expected the rubber membrane inside the accumulator was gone.

    I refreshed my whole rear suspension and it was really worth the effort. The ride quality has improved dramatically. And even after 3 months in the garage the ride hight on the rear axle is unchanged. The car does not lower itself when time goes by.

    Some pics

    old accumulator
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    new accumulators - bad pic from the manufacturer, my mechanic did install them without taking a pic so this is the only one I have....

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    other parts

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    installed

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  6. Schumi

    Schumi Formula Junior
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    Jun 5, 2002
    674
    Missouri
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    Daren
    That last photo is absolute art. Someday mine too will look like that.
     
  7. samsaprunoff

    samsaprunoff F1 Rookie
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    Jun 8, 2004
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    Edmonton, AB Canada
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    Sam Saprunoff
    Agreed... Those pics of the restored suspension are fantastic!

    Cheers,

    Sam
     
  8. Mark Shannon

    Mark Shannon Formula 3
    Silver Subscribed

    Dec 28, 2003
    1,030
    Surrey, UK
  9. wrxmike

    wrxmike F1 Veteran
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    Mar 20, 2004
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    Michael

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