400i Spring Change

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

 

Bummer
Makes me want to get rid of my self-leveling system even though it's working fine!
Here's what I grabbed from here a while back:
View attachment Pg1.rtfd.zip
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View attachment Pg14.rtfd.zip
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View attachment Pg16a.rtfd.zip
View attachment Pg16b.rtfd.zip
View attachment RearKoniLevelerHandbook.pdf

 

Please let us know on all the specifics when you've made your choice.

 

I'm going to need this soon also.

 

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

 

Found this on the GTC4 site. Unfortunately you can't participate in the site unless you own one, but can still get some good info from it.

Springs made for rear - 365 GTC/4 Assistance - Ferrari 365 GTC/4 Forum

 

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.

 

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

 

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.

 

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...

 

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.

 

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

 

When you take the Koni system out, you replace with two coil overs per side.

 

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

 

Oh, I was so hopin' that the link took me to a place where I could acquire NOS load-levelers

 

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

 

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
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!

 

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

 

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?

 

...and we're all jealous of that fact

 

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

 

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.
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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?

 

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.

 

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?