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Shock/Lowered Suspension Question

Discussion in '348/355' started by 16v2911TT, May 22, 2017.

  1. 16v2911TT

    16v2911TT Karting

    Oct 4, 2013
    101
    LA | OC | SD
    I lowered my F355 over the weekend via the factory coilovers (going off of this: Lowering Ferrari 512TR, 348, F355, 550, Mondial T?) and took it for a drive today before the alignment.

    Am I supposed to change the shocks as well to keep it from bottoming out or is this normal (I had a KWV3 system in my last car that was pretty low but did not bottom out, so I'm not sure)?

    I was also going to install a set of H&R springs as well but I'm holding off for now.
     
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  3. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
    5,990
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    What is bottoming out? If it's the dampers themselves you will damage them in very short order. In that case you are outside of the working parameters of the current components. You would need to change to a stiffer spring *and* change to a damper design that won't bottom out under full compression or revalve the existing dampers to work with the stiffer springs and install progressive bumpstops. I'd suggest discussing the issue with someone familiar with 355 suspension components, such as Delta Vee Motorsports.
     
  4. 308 GTB

    308 GTB F1 World Champ
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    How much did you lower your car? Did you start with your car set at the factory ride height?
     
  5. schnazzy

    schnazzy Formula Junior

    Mar 31, 2008
    483
    Seattle
    OP, do you NEED to change the shocks now that you have lowered the car? No. SHOULD you? Maybe.

    Assuming these are factory shocks and are in good condition and don't need to be refurbished or replaced, this should be fine. If you replaced the springs or just cranked the suspension down to the ground then you may consider getting something more correct.

    If you dropped it .5" or so you don't need to swap them. You shouldn't bottom out on the shocks with the stock springs no matter the height. What you may find though is that with the tighter spring (from compression to lower it) the stock shocks do not provide enough dampening at speed or on the track.

    You can probably get much more superior shocks on the market today as compared to your ~20 year old factory ones.

    I dropped mine 1" in the front and .75 in the rear. Kept the stock shocks for now (may have them refurbed at some point).
     
  6. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,415
    These crs are absurdly low at factory settings.
     
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  8. 16v2911TT

    16v2911TT Karting

    Oct 4, 2013
    101
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    I can't tell exactly what's bottoming out...frankly, the moment it happened, I just about stopped driving the car altogether.

    I've tried emailing and giving Delta Vee Motorsports a call (to both numbers) and I haven't heard back - would you happen to have a better contact for them?

    Started at factory height, lowered .85 in the front, 1 in the rear.

    What aftermarket shocks did you replace your OEMs with?
     
  9. schnazzy

    schnazzy Formula Junior

    Mar 31, 2008
    483
    Seattle
    "What aftermarket shocks did you replace your OEMs with?"

    I dropped mine 1" in the front and .75 in the rear. Kept the stock shocks for now (may have them refurbed at some point).
     
  10. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    The Challenge cars use stock factory shocks. They did use rears in the front because they needed more aggressive valving than the fronts were capable of and they ran a different control unit. Camber adjustment really limits how far you can go. There are only so many shims you can remove to reduce the ridiculous camber lowering causes.
     
  11. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
    5,990
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    Frankly, I figured you'd slammed the car and had bottomed the dampers but that seems less likely now that you've elaborated. I'm not familiar with 355 suspension setup, but .85" and 1" below factory ride height doesn't seem like it should bottom the dampers except *maybe* under extreme circumstances. I wonder if there are other factors at play here. Are you running stock wheels and tire sizes?

    You were wise to stop driving the car until you can sort out the issue but some further investigation is in order. If it were mine I'd pull the wheels and examine them and the tires for any signs of contact, as well as closely examining all of the suspension components for clues. While you're in there put a cable tie around each of the four damper shafts. Tighten them enough that they won't slide on their own, but not so tight that they'll damage the top seals on the dampers. Be sure and trim the leftover part of the tie and don't leave any sharp edges. That way you can determine just how much excursion the dampers are experiencing, which may help determine whether or not the suspension is too low for the dampers.

    One note on H&R springs-- they are intended to help prevent bottoming of the suspension when lowering a car, so they might be useful here, although they're stupid-expensive for our applications. H&R lowering springs are progressive rate in order to maintain decent ride quality but they stiffen up under further compression to reduce the chances of bottoming under extreme circumstances. They're really a better way of lowering the car because they help keep all of components more within their operating parameters. Not that I'm suggesting that you should lower the car more, only that lowering the car .85" and 1" would better be done using H&R lowering springs in conjunction with adjusting the perches, as opposed to simply lowering the perches.

    Of course, that's assuming that Delta Vee doesn't have a better solution. Considering what H&R wants for 355 springs it's worth checking alternatives before considering H&R. And no, I don't have any other means of contacting Delta Vee. Sorry.

    Can you post a pic of the car as it sits now?
     
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  13. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Interesting. Now that you say it I remember seeing that elsewhere. Of course, it's important to consider that the Challenge springs were a good bit stiffer, so it's possible that the damper excursion is actually greater on a lowered street car.
     
  14. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
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    And I think they had 2 rates to choose from.
     
  15. 308 GTB

    308 GTB F1 World Champ
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    Yes. F355 Challenge springs came in two spring rate pair varieties:

    1800 lb/in Front and 700 lb/in Rear
    2200 lb/in Front and 900 lb/in Rear
     
  16. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
    5,990
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    With rates like those you're probably not going to bottom the damper. :)

    But that's hopefully not what's going on here anyway if the car has only been lowered an inch. I had assumed that he'd slammed the car based on his first post.
     
  17. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    20,013
    socal
    Lots of things going on with the 355 and they must be looked at in context. Bottom line if you are bottoming your car is now slower than it was before regardless of how it feels. A bigger spring will just disguise when you bottom and go slower.
     
  18. 16v2911TT

    16v2911TT Karting

    Oct 4, 2013
    101
    LA | OC | SD
    #15 16v2911TT, May 23, 2017
    Last edited by a moderator: Sep 7, 2017
    I actually had already bought the H&Rs but I don't have a spring compressor, and I was free this weekend, so I followed those guidelines on lowering via spring perches.

    I'm going to swap springs and get it aligned.

    Thank you guys for the replies!
    Image Unavailable, Please Login
     
  19. taz355

    taz355 F1 Veteran
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    Feb 18, 2008
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    Grant
    What tire sizes you running?

    Is it possible your tires are rubbing??
     
  20. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Like I said, I'm not familiar with 355 setup (I do track prep & suspension work, but on other marques) but I've seen lower 355s running on OE dampers, so unless there's something wrong with them I have a hard time believing you're bottoming the "shocks". Which is not to say that the dampers wouldn't benefit from a rebuild, but that's another topic entirely.

    Since the H&Rs are lowering springs you'll need to raise the perches to achieve the current ride height. In fact, you might even need to raise them higher than they were originally. This is where setup comes into play-- you want to focus first on the desired (hopefully practical) ride height but you also want to consider corner weights before you go to the expense of aligning the car. You can set the basic ride height yourself but unless you have access to a set of scales the final adjustment should be performed by a race shop or someone with a good working knowledge of corner weighting.

    Setting one of these cars up correctly is akin to $etting up a race car, but the end result will be worth the effort.

    In any event, I'd still test for bottoming before paying for a proper setup because it's entirely possible there's something else going on.

    Pretty car. Got more pics? Looks like you have red interior and I know we have some fans of those here. :)

    Good luck and let us know how it all shakes out.
     
  21. 16v2911TT

    16v2911TT Karting

    Oct 4, 2013
    101
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    The spring install and alignment (and most likely corner balancing) will indeed be done by a shop and yes, the springs will drop the car further so the perches will need to come back up. Thank you again for the insight, Mike. I'll have more photos soon!
     
  22. INTMD8

    INTMD8 F1 Veteran
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    Jun 10, 2007
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    What is the spring rate of the H&R vs stock?
     
  23. 16v2911TT

    16v2911TT Karting

    Oct 4, 2013
    101
    LA | OC | SD
    Trying to get that information from H&R now, although...it might be in this forum somewhere. I'll have a look.
     
  24. fatbillybob

    fatbillybob Two Time F1 World Champ
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    Aug 10, 2002
    20,013
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    I thing H&R spring rates are top secret. I use Hyperco's because I swap springs all the time on street and race cars. Hyperco is intelligent where you can ID a hyperco spring instantly. I reward intelligence by using Hyperco's.

    part numbering system for Hyperco srings:
    :
    The part number comprises:

    FREE LENGTH + ID CODE + RATE

    For example, Hyperco’s part number: 10 B 0400 would have:

    (1) A 10” Free Length

    (2) A 2.5” I.D. (they have code list B=2.5" etc.)

    (3) A rate of 400 lbs. / inch of spring deflection.
     
  25. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
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    Rob Schermerhorn
    F355 Challenge uses the exact same damper PN front and rear, which is different vs road cars. With the exact same valving in the damper, it is the suspension ECU which optimizes damping front vs rear.
     
  26. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
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    Rob Schermerhorn
    A one inch drop in ride height with OE springs will not inherently cause bottoming under "normal" driving conditions. That said, obviously, it will be easier to strike the bump rubbers.

    Speaking of bump rubbers, Ferrari used much higher quality BASF Celasto microcellular polyurethane on the 348, then switched to cheaper synthetic rubber for F355 (and 456, F550, etc). Microcellular polyurethane is exponentially superior in spring rate characteristics vs rubber, more progressive. So a change to better bump stop material will improve ride quality.
     
  27. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
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    Rob Schermerhorn
    Just so others in this thread know, we did exchange emails, I requested ride height and alignment information and did not receive that info...
     
  28. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
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    Rob Schermerhorn

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