Ferrari 400i shock replacement

I thought I would post this up here just for info.

I had a 400i in the shop with leaking rear shocks and the actuator was also leaking. The shocks could have been rebuilt but the actuator was actually a much tougher nut to crack. The cost of the shock rebuilds as well as the other items that needed replacing was about the same as changing to standard shocks.

I ended up replacing the rear shocks with a standard mechanical system. The shocks are Ohlins and they have 150# spring on them. The blanking plate was just machined out of a solid chunk of aluminum.

The car rides well and while the original load leveling system worked well, the availability of parts has made this change practical.
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Yes They were done by PSI Performance Shocks Inc in Sonoma CA. www.performanceshock.com
They will rebuild your Koni shocks but if the actuator is bad the parts are not available
The shocks are Ohlins NCJ 1960 with CX20 RX25 valving.
The springs were actually 1200.250.0110 which translates to 12" tall 2.5" ID and 110 lbs/in - previously I had incorrect wrote 150lbs/in

These were custom made so that they bolted into the car in my shop, without modification, by PSI. They were a bit pricey with a total cost of around 3200.00, but then again just the ohlins and the springs accounted for 2k of the bill and the remainder was in the custom fabrication. The blocking plate was done by the guy who is taking over my shop. He is a pretty good machinist and it took him about an hour to complete and we charged 100 bucks for it. If there was a real demand for the blocking plates we could probably make 10 in an hour 20 and get the cost down to 40 or 50 bucks.

As a side not I am retiring out of the business but have a young guy, Jon McClendon, who is taking over for me, and he is pretty good. His background is with BMW's and he is an A&P certified aircraft mechanic. My shop is an Italian car shop with most of my work is on Alfa Romeo's but we do a fair amount of Ferrari and vintage Lancia work. Jon did most of the work on this 400 where I just gave him guidance. So if you are in the Raleigh Durham area in NC and need assistance give Jon a call. We currently work on cars up to 360/456, Jon can be reached at [email protected].

 

It is a 1984 series 2 car, and it is not my car it is just in my shop getting repairs.
I don't know all the intricacies of the 400 series of cars, so I can't tell you differences between series 1 and 2, but my understanding is that this suspesnion started in about 1979 and carried over to the 412. On earlier cars like the 365 2+2, which I think most of the 400 evolved from, they used a single shock on the rear suspension, and this is probably what is on the earlier 400 series but I do not know for certain.

Kevin

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Can you elaborate on this. I have looked at the suspension and I understand what Ferrari was doing with the load leveling device and the sway/torsion bar, but I cannot understand why it is of any use now.

 

No I am a suspension engineer and I am still trying to figure out its usefulness

 

Ok the vehicle has completely lost the hydraulic system. The original system just used the sway bar as a torsion spring, a good idea for controlling ride height but not for suspension control. Putting a rod or some other mechanical contraption is just a very inefficient spring system, as the pickup point for the stabilizer bar is 100mm closer to the pivot point than the shocks.
Yes I am giving up ride height control. I set the ride height when having 350lbs of nominal load and this allows an additional 300 pounds of load. Or another way of looking at it if you put 2 dead bodies weighing a total of 400lbs in the trunk the rear suspension would go down about 1". But A) you don't have the room and B) at your max capacity of 300 Lbs and at 300 you are only looking at about 3/4" drop. I think I can live with this.

As far as NVH it really hasn't changed. Jaguar and Maserati (QPIII) both use a similar 4 shock setup and the Ferrari's load path's are better than either. Despite their foibles both Jag and the Quatroporte are known for their excellent ride without the need for load leveling. The 400 does very well going down the road and it reminds me of driving my 94 XJS. They are both a bit of boats and are more cruiser/GT's rather than sportscar, but they are nice cruisers, and it handles well for a cruiser. Your analysis of spring rates really doesn't hold up, a lot of this is down to just superior shocks than what it came with originally, 40 years of innovation will do that.

I can't really say there are a lot of Europeans that do offer this system. Mercedes definitely did but generally on their big boats, not on something like the R107 which is closer to the 400i size and duty. BMW offered it as an option on larger cars, but BMW thought their cars rode and handled well enough that it was only an option. Citroen had the really state of the art system, but it was rather complex and costly to keep up, particularly in the states. RR uses a system that I know nothing about. Oh also there is a big business in retrofitting the hydraulic system to standard springs and shocks on the German stuff.

Mercedes and BMW also both used trailing arm rear suspension which will give you camber changes with ride height changes. The 400 uses unequal length double A-arms which do not give you the camber changes, so their is no loss of correct geometry.

Now again I ask is there a legitimate reason to put something in place of the ride height cylinder that I removed.

 

You are right I screwed that one up. The sphere are basically changing the spring rate.

 

It probably does, but at a minimal amount, and the tire should never lean out. But my point was comparing SLA to a trailing arm suspension which has relatively huge camber changes. In theory a SLA will have zero camber changes, just as Dedion has zero, but in reality due to deflections mostly in rubber they design in a degree or so for street cars and closer to 3 for track cars