Need help: inconclusive info about ride height and rake on my 355?

[johan355GTS]

I have just finished changing my spring and am sitting thinking about ride height and rake. After reading the article by Mitch Alsup, I have understood that rake and ride height is very important for the handling and behavior of the 355.

Reading through the technical manual I see that the recommended setting for the 355 is 162-171 in the front and 182-191 at the rear. This gives a diff (or rake?) of 20 mm front to rear. The rear is 20 mm higher than the front.

My car had originally 165 mm in front and 200 mm in the rear and I am pretty sure this was factory settings by the reading of markers on the damper etc. The car is for some reason 10 mm higher than the manual at the rear from the factory. The diff becomes 35 mm (was the higher rear from factory done to give more over steer?)

The new spring has lowered the car to 145 mm in the front and 190 mm at the rear, the diff is now 45 mm! I have seen different recommendations of combinations in ride height but am not sure of where to start.

All measurement was taken at the lower suspension arm bolt as described in the manual.

So to my dilemma; I have read all I can find on this subject at different Ferrari forum but can come to a conclusion. I want to get to a reasonable rake where I can start tuning in for the correct over/under steer without going to extremes. I have driven the car as it is now, no changes made yet to camber and toe in etc. And so far I like the change but I am not sure what will happen as I change camber and toe in back to factory spec. The new diff of 45 mm sounds extreme to me but I can’t really say the car felt that different as I drove it yesterday. Surely it was more nervous but it cornered so much better, steering in to corner felt superb and the gain in steering control gave me confidence in at high speed.

Can some one please help me decide what to do!

[fatbillybob]

reset to factory rake. You can adjust ride height all over the place with the new springs and perch position relative to the spring. reset the factory alignment too. Then test drive. Unitl you are near limits you really cannot access the changes. Then once you are sure you have understeer or oversteer tune only one end of the car. I like to tune from the rear by adjusting ride height and tire pressure to change rear grip assuming a reasonable amount of rear toe. I do not use camber setting to change grip but use camber to control contact patch and tune for even tire temperature of hot racing slicks. Don't forget about braking. Rear height changes braking feel at the limits.

[Racer86]

You must do a corner weight set up. You can't just wind the spring perches up or down and measure ride height on god knows what unlevel surface and get your car to handle. It must be corner weighted correctly. You sound like a smart person, but just to start the corner weight image in your mind, think of a table with one short leg. That is what your car will be like if you have a corner that is not loaded with its correct weight.
Do your aligement, set a base ride height, set tire pressures, disconnect sway bars, get car on surface plate with the scales (or a shimmed to level floor) and set the corners to have a good diagonal cross weight( LF to RR, RF to LR) with the front weight (left to right) as close as possible. your ride height should be still close, but corner weights are more important. Just trying to help you get the handling you want. But you have to do the basic setup so you know where the suspension and weight is at before you can really start to tune it for the feel you want.

[johan355GTS]

I know about the corner weight, the tricky thing is to find some one who has the tools to do it. I am thinking of buying a set of acales just because I can find anyone that can help me. Thanks for all the input!