Rear Suspension Behavior | Page 2 | FerrariChat

Rear Suspension Behavior

Discussion in '365 GT4 2+2/400/412' started by Highmiler, Mar 26, 2016.

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  1. 57Wayne

    57Wayne Karting

    Mar 29, 2015
    127
    Wilbraham MA
    Full Name:
    Wayne Thresher
    I went onto Summit Racing site last night and bought the QA1 parts included in the .pdf document. Numbers are slightly different and prices have shifted a little:Shocks are DS602-QA1 ($160.97 ea), Stud top conversion kit is SS110SDM-QA1, $34.97 ea, and springs are 10HT250-QA1, $46.97 ea. Note that the QA1 is sometimes listed in front of the PN (invoice) and sometimes after (site search). The other part of the PN is the manufacturer PN that you can search for at other places.
    My car pumps up nicely but doesn't hold long after shutting down. Within an hour it is in roadscraper stance in the back. When pumped up, the ride is fine; would that indicate an issue with just the accumulators?
    Figured this shock change is fully reversible, so not much to lose...unless just changing the accumulators to the Mercedes units would have done the trick!
     
  2. wrxmike

    wrxmike Moderator
    Moderator Owner

    Mar 20, 2004
    7,573
    Full Name:
    Mike
    #27 wrxmike, Aug 19, 2016
    Last edited by a moderator: Sep 7, 2017

    No,I think it's the flluid draining back to the reservoir at the front of the car. The reason is either the adjustment of the position of the height sensing valve (1) or an internal leak inside the valve.
    The pupose of the valve is to allow hydraulic fluid from the pump to flow to the shocks if the rear of the car is too low, or bleed from the shocks if it too high. When set up properly the valve is in the neutral position when the car is at the correct height ( engine running). With the engine turned off (over time), a small amount of fluid leaks past the piston seals in the height adjusting valve and returns to the reservoir and this allows the car to settle.
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  3. 57Wayne

    57Wayne Karting

    Mar 29, 2015
    127
    Wilbraham MA
    Full Name:
    Wayne Thresher
    Thanks for the figure of the rear, it helps a lot! Is Item 1 in the figure the height sensing valve? (I'm thinking that was what you are indicating in your note). Is there any more information on how it works and the guts of it if I were to disassemble it?
     
  4. Newman

    Newman F1 World Champ
    Consultant Owner Professional Ferrari Technician

    Dec 26, 2001
    14,092
    Canada
    Full Name:
    Newman
    Yes it is and interestingly (at least to me) this determines the type of tool kit the car comes with. Why you all ask? Because the spare now has to sit face up in the trunk meaning no more space for a brief case to fit in the back side of the spare. The tool kit is a kidney shaped soft case that sits in the front face of the spare wheel on a 400 with the height sensing valve.

    Its most likely a spool valve inside that cylinder. Seals or metal to metal? Let us know when you take it apart.
     
  5. wrxmike

    wrxmike Moderator
    Moderator Owner

    Mar 20, 2004
    7,573
    Full Name:
    Mike
    Yes, Item 1
    I'll try and post the section of the WSM that shows how it's supposed to be set up.
    I've not found any information about the internals, I believe it's a spool valve as Newman posted and suspect it's probably an item that Ferrari sourced from industry, rather than specifically made. Mine works ok and doesn't leak, so I haven't tried pulling it apart.

    M
     
  6. John Wetzig

    John Wetzig Rookie

    Aug 2, 2012
    45
    Allentown PA USA
    Full Name:
    John Wetzig
    For Newman and any others with Series 1 cars with the correct ride height. Can you tell me the number of coils, uncompressed height and anything else that might relate to the springs. I've been told that there are two different sets, and that my car might have the wrong set, contributing to its low rear end.

    Thanks.

    John
     
  7. 57Wayne

    57Wayne Karting

    Mar 29, 2015
    127
    Wilbraham MA
    Full Name:
    Wayne Thresher
    I've put the QA1 shocks on the rear and made a list of the details to accomplish it (maintaining hydraulic on the forward shocks in the rear). One last bit: Using the bottom of the rocker in front of the rear wheel as a point of measure, what is the height off the ground for correct ride height? I am about 1/2 inch (1.27 cm) higher unloaded than it was prior to changing.
     

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