400i Spring Change | FerrariChat

400i Spring Change

Discussion in '365 GT4 2+2/400/412' started by Indy430, Aug 14, 2013.

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  1. Indy430

    Indy430 Karting

    Dec 5, 2007
    210
    Indianapolis
    Full Name:
    RJ
    Hello all. I have a question on spring rates on the rear of a 400i. Background:

    1983 400i

    Koni leveling system has given up and instead of fixing it yet again it is going away. I am changing over to QA1 coil overs in the rear. My question is spring rates. I did a search here and couldn't find anything about it. I did see on a FCA tech forum of a guy that used 150 lb/in springs in his, and he used the QA1's as well, but I haven't been able to locate him as his post was from 2004. That sounds really low to me for the weight of the car, especially when you put 300lbs of gasoline right over the rear. I understand that there are 4 shocks back there, but in my 1100lb race car I use 400 lb/in springs in the rear. Now I know that is a race car but the 400i weighs 5 times as much as that car. Looking for a little guidance.

    Thanks
    RJP
     
  2. blkprlz

    blkprlz Formula 3

    Mar 24, 2007
    2,169
    Tampa bay
    Full Name:
    Bruce
    Please let us know on all the specifics when you've made your choice.
     
  3. Ak Jim

    Ak Jim F1 Veteran
    Owner Rossa Subscribed

    Dec 23, 2007
    8,451
    North Pole AK
    I'm going to need this soon also.
     
  4. aidanparte

    aidanparte Formula 3

    Jul 18, 2004
    1,222
    RJP

    Did you ask QA1 for recommended spring rates? My series 1 400i doesn't have the self-levellers, but I don't know what the spring rates are. Perhaps an owner of an 400 or early 400i might know. BTW, Jody Scheckter stiffened the springs on his 400A to improve the handling. Are you going to do your fronts as well?

    Aidan
     
  5. Ak Jim

    Ak Jim F1 Veteran
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    Dec 23, 2007
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  6. GT Jones

    GT Jones Formula Junior

    Oct 15, 2011
    669
    Lincoln, MA
    Full Name:
    Christian J
    I've been looking into this a bit as well and from multiple sources I found the rate to be 150lbs. However, I saw that T Rutlands offers a single adjustable Koni coil over ($1200 pr!) that was reportedly engineered by Koni to have correct valving. The QA1's are said to have less sophisticated valving than the Koni's and much less than the high end options like Penske. I think my levelers will get me through the rest of the summer and this winter I will replace the along with rear bushings. I plan to pull all of the shocks and run them on a shock dyno to see what i'm working with and if I can uprate things slightly. Right now id say my shocks are shot in the rear and springs are a bit soft/low all around.
     
  7. islerodreaming

    islerodreaming Formula 3

    Aug 11, 2007
    1,427
    Full Name:
    John - a proud Australian man
    PM Greg246 on this site. He did this to the back of his C4 a couple of years ago. Or search his posts (there are a few) he posted pictures of the work.

    John
     
  8. lmaldoon

    lmaldoon Rookie

    Feb 5, 2005
    30
    La Quinta CA
    Full Name:
    Lee
    I did this a few years ago and started with 4 250's and found it too stiff. I lightened to 225's but that is still a little stiff. 200's or even 175's would be about right. I will need to look up the shock model number but it has the lower damper adjustment knob.
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,041
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    You might want to focus more on the wheel rate rather than the rate of the spring alone in your comparison thinking. Your 400i has two things (the shocks being mounted nearly vertical and the mounting point of shock being very far outboard on the A-arm from the pivot axis) that result in a very low geometry effect. On many cars, the wheel rate can be 2~3X lower than the total spring rate from the geometry factors; whereas, on your 400i, it might be only be ~30% lower than the total spring rate -- just an observation of the design...
     
  10. Ak Jim

    Ak Jim F1 Veteran
    Owner Rossa Subscribed

    Dec 23, 2007
    8,451
    North Pole AK
    Ok, I have a question. Each rear A arm has two shocks. Only one of the shocks has a spring on it. I would think that would put a strong twisting force on the A arm. If you would go with new shocks and springs why not use two springs on each side? Of course the springs would not need to be nearly as strong.
     
  11. Indy430

    Indy430 Karting

    Dec 5, 2007
    210
    Indianapolis
    Full Name:
    RJ
    All,

    Thanks for all the help! I talked to my shock supplier yesterday (QA1) and we are going ahead with the 150 lb springs first and see where that leads us. I can always swap the springs to a stiffer spring. As soon as they are on I will take some pictures for you guys and give a review.

    Thanks!

    RJP
     
  12. Indy430

    Indy430 Karting

    Dec 5, 2007
    210
    Indianapolis
    Full Name:
    RJ
    When you take the Koni system out, you replace with two coil overs per side.
     
  13. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    #14 Steve Magnusson, Aug 15, 2013
    Last edited: Aug 15, 2013
    That's true for a 365 GT4 2+2, but not for a 400i -- 400i has two stock springs on each side to better not twist things (as you noted):

    365 GT4 2+2 (one large spring on a separate damper and a passive self-leveling gizmo without spring?):
    http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=3911

    400i (two identical active pump-driven, combination damper+leveler units and 2 smaller springs):
    Ferrari 400i Parts : Table 50 - REAR SUSPENSION - LEVERS AND SHOCK ABSORBERS

    http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=3320
     
  14. blkprlz

    blkprlz Formula 3

    Mar 24, 2007
    2,169
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    Bruce
  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,041
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    Steve Magnusson
    #16 Steve Magnusson, Aug 15, 2013
    Last edited: Aug 15, 2013
    NOS with 30 year old rubber bits inside? Wouldn't help you ;)

    Koni won't rebuild? I thought your 365/400/412 cabal in Europe was/is fairly strong. Since so many have converted back to a completely passive system, there should be many cores available to fiddle with or send off to Koni -- no?

    Interesting example of design evolution meeting a difficult-to-solve problem -- can't fault them for trying to not add huge complexity in the 365 GT4 2+2 design (no pump, no plumbing are a definite reliability plus), but they obviously punted on the 400i and went to a straight-forward, symmetric system with pump and plumbing -- which, maybe, just proved that using huge complexity, to solve some other problem, is just a problem itself ;)
     
  16. blkprlz

    blkprlz Formula 3

    Mar 24, 2007
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    Bruce
    I don't know Steve...
    Yeah, I know...there are cars out there that had the systems fail on them. It's like anything else, negative reviews tend to overwhelm the positive just because they need tending :(
    Mine is still working fine after 30 yrs. :) & I'd rather have mine rebuilt when the time comes but if Koni's bailing on their own engineering...shame on them :mad:
    I'll switch in a heartbeat & never use them again, even if they continue to be the elite performer...you don't know what surprises will come out of their sleeve!
     
  17. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,591
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    Here is contact for a shop that rebuilds all Koni's including "ours". He did two for me and is very meticulous:
    Jeff LeBlond
    FJB LLC.
    623-566-1628
    [email protected]
    FJB Limited - Koni Shock and Lamborghini Specialists

    I bought two NOS (30+year old) and they are working fine. I had one leaker, and I found two NOS so I swapped out two. Jeff rebuilt the leaker and its mate on opposite side and they are on standby for future use.
    Ken
     
  18. Ak Jim

    Ak Jim F1 Veteran
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    Dec 23, 2007
    8,451
    North Pole AK
    Maybe I should have mine rebuilt. I haven't looked yet but the right side of the car is 1 1/2" lower than the left. This seems to have happened almost over night.

    I was impressed with the way it worked up to that point. On our big trip we had 4 people and the trunk stuffed to the max. With all of that weight plus full gas the car didn't sag at all and conversely when the car was empty it didn't go up either.

    If I do get the Konis rebuilt how long does the rebuild last? Is it as good as new?
     
  19. dstacy

    dstacy F1 World Champ
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    Jan 23, 2006
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    Dave
    ...and we're all jealous of that fact
     
  20. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,591
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    Jim
    Jeff rebuilds them with complete new seals and orifices. With respect to rubber seals they should be better than 1980 vintage rubber when new. Modern oil is probably better also with respect to seals. I am sure Jeff will find that you have a lot of sediment in the housings; he is quite big of oil changes for hydraulic system. Call him and have a chat, be sure you have a few minutes to spare.....
    Ken
     
  21. GT Jones

    GT Jones Formula Junior

    Oct 15, 2011
    669
    Lincoln, MA
    Full Name:
    Christian J
    #22 GT Jones, Oct 15, 2013
    Last edited by a moderator: Sep 7, 2017
    What started as a rear bearing replacement has morphed into a rear suspension refresh. Does anyone else have green coils? These are still pretty dirty but I swear they are green. Free length is a little short at 16 1/8.
    Image Unavailable, Please Login
     
  22. Ak Jim

    Ak Jim F1 Veteran
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    Dec 23, 2007
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    Man, I'm getting pumped up about starting my rear suspension rebuild! Thanks for all of the links and pictures. I'm in the middle of rehearsals for a musical right now so I'm pretty busy with that. I do think starting in November I can get started. I'm wondering if I should pull the fronts off and have them rebuilt at the same time?
     
  23. GT Jones

    GT Jones Formula Junior

    Oct 15, 2011
    669
    Lincoln, MA
    Full Name:
    Christian J
    I'm pretty sure these are aftermarket springs after looking at approx 100,000 threads on Ferrari suspension rebuilding. Can anyone confirm that green springs are oddballs? Why read a mystery book when you can work on a 35 yr old Ferrari with no service records prior to 2008?
    Jim, I think you should do one side at a time so you can refer to a complete assembly.
     
  24. GT Jones

    GT Jones Formula Junior

    Oct 15, 2011
    669
    Lincoln, MA
    Full Name:
    Christian J
    I cleaned up the springs and can find a small yellow sticker that reads A. CAGNOLA in the center. Other sources have said they are OEM springs on 308s. What??? Does anyone else here have green coil springs on their 400/412?
     

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