Suspension Adjustments | Page 2 | FerrariChat

Suspension Adjustments

Discussion in '308/328' started by PDB, Apr 8, 2017.

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  1. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    24,997
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    Using the dimensions in the 308GT4 WSM, for each 1mm change in the shim thickness = a .266 deg change in camber.
     
  2. 328GTB

    328GTB Formula Junior
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    Jun 4, 2002
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    Carmine
    What's the math? I tried ATAN (1/215) but it doesn't seem right.
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    24,997
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    That's the math I used exactly -- make sure your calculator is in "degree" mode (not "radians" mode).
     
  4. 328GTB

    328GTB Formula Junior
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    For reference for 328GTB until Vin 76625

    Front: 0.201 deg/mm (atan(1/285))
    Rear: 0.255 deg/mm (atan(1/225))
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    24,997
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    Did you find a F reference drawing with those dimensions, or did you just measure your early 328?
     
  6. 328GTB

    328GTB Formula Junior
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    Yes. Page 44 of the "328 tech specs" document:
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  7. 328GTB

    328GTB Formula Junior
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    Jun 4, 2002
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    FoH provided these spring measurements from a 1986 328GTS in their shop for new shocks:

    Front: 368 mm (almost an in taller than mine)
    Rear: 381 mm (close enough to mine)

    The PN are the same between the early GTB & GTS. But the GTS is 33LBs heavier. Could that account for the discrepancy on the front springs?
     
  8. dwhite

    dwhite F1 Rookie

    #33 dwhite, Feb 12, 2019
    Last edited: Feb 12, 2019
    One thing I would say is the stock settings can be tweaked if you have a true chassis/suspension set-up guru.

    I had both my Boxer and 308 suspensions completely redone when I bought each car, as I wanted them to drive like new. The person was a chassis set-up expert and he tweaked the stock setting a bit to get even more out of the car, but not radical to cause faster wear. He called them a more modern setting. Cornerweighting was part of the setup as well.

    Check your springs to see if they are equal in lbs at the correct conpressed height. Looking at them unsprung, probably won't give you much valuable info.
     
  9. 328GTB

    328GTB Formula Junior
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    For that, I would need the static load weight spec for the 328 springs, which is nowhere to be found.
     
  10. dwhite

    dwhite F1 Rookie

    #35 dwhite, Feb 12, 2019
    Last edited: Feb 12, 2019
    You should be able to comfirm they are equal spring rates. Take them to a shop. They should have a compressor to check the rates. I think I have seen stock spring rates mentioned on fchat in the past.

    I think 308 springs are 200lbs all around, not sure if 328s were identical. Each 200 lbs drops spring 1 inch, 800 lbs = 4 inches.
     
  11. 328GTB

    328GTB Formula Junior
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    I’m soliciting feedback on toe-in and how’s measured. Per 308GT4 WSM, page G6, it looks like the toe-in spec is measured between the edges of the wheel rim. Is that indeed the case?

    There’s also this comment on the same page next to Fig. 3:
    In case that toe-in is not within the prescribed values, operate on the front forks of both suspension control arms then duly vary the thickness or quantity of the washers.

    Are they talking about adding/removing shims on the front wishbone connection to the chassis?
     
  12. PDB

    PDB Formula Junior

    Feb 1, 2011
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    I would have assumed that was for the rear suspension, not the front.
    Adjusting the steering control arms is the usual method for front toe.

    Paul
     
  13. 328GTB

    328GTB Formula Junior
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    Front camber degrees as a function of mm shims is not exactly linear. Any thoughts?
    Notes: Loaded suspension on a level ground.

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  14. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Ehh - close enough ;)

    It's not like you are wringing steel gage blocks together -- the whole system has a lot of flexible components affecting the final result. The math calculation just gives a rough guess for a first guess for what to do -- needing to do a second smaller tweak to the shim thickness change isn't unreasonable. Even just measuring/remeasuring camber (after rolling the car around some) has a fair bit of variation.
     
  15. nerofer

    nerofer F1 World Champ

    Mar 26, 2011
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    Perhaps this is what you have in mind, for the very early cars?
     

    Attached Files:

  16. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Back when I was doing a lot of alignments with really good equipment I tried to make a chart for the cars that used shims on changes to camber for every MM of shim change. I remember quite clearly the change was not linear. A 2MM change was not = 2x 1MM change. And it was different for different cars so I threw in the towel. It became too much work.
     

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