SPRING RATES & DROPS: ALL IN ONE THREAD!!

Discussion in 'Suspension, Brakes & Chassis' started by Gibbo205, Feb 17, 2016.

  1. prem

    prem Well-Known Member

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    I called Eibach and they mentioned their eibach prokit is a linear springs and not progressive but the shared document says otherwise
     
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  2. dsp4848

    dsp4848 Well-Known Member

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  3. prem

    prem Well-Known Member

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    Yes i did mention that their website and the other vendors listed them as progressive but the person over the phone reconfirmed with the R&D guys who actually worked on it and he mentioned their sportline kit is progressive which i very evident from the pics
     
  4. dsp4848

    dsp4848 Well-Known Member

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    Yeah, I always thought the Pro Kit looked linear and just took their word for it being progressive. Did he happen to say what the spring rates were?

    If they are linear, that kind of seems like a big deal, since they are advertised everywhere as being progressive and I'm sure some people buy them for that reason. If one of their R&D guys said so, I would trust that more than a sales guy. Very interesting, I'd really like to know the true answer. Thanks for posting that bit of info! :thumbsup:
     
  5. prem

    prem Well-Known Member

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    the rates are same as whats posted in this thread or anywhere.. Front: 200-314 lb / in. Rear: 800-914 lb / in
     
  6. dsp4848

    dsp4848 Well-Known Member

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    Yeah, I agree with you that those are the advertised spring rates, but those would be for progressive spring rates. A linear spring rate should be a single number, not a range.
     
  7. K-Roll302

    K-Roll302 Well-Known Member

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    #142 K-Roll302, Nov 11, 2016
    Last edited: Nov 11, 2016
    So I'm given to understand that the Ecoboost PP springs are linear, so there shouldn't be much of a noticeable difference in ride quality if I go with linear lowering springs then? Compared to if I were to go with progressive springs? I want the a spring that does better than the EBPP spring in performance but doesn't compromise too much on comfort.
     
  8. prem

    prem Well-Known Member

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    Had the steeda progressive springs yesterday and very happy with the drop and stance of the car. I didn't see much difference in ride quality over my stock pp springs. I thought it was about as stiff as the stock ones or may be tad bit little less stiff.. Handling defintely improved
     
  9. Niz55

    Niz55 Well-Known Member

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    Change out the bmr handling to 1.6 -1.7 drop on the front. 1.2 is not accurate at all.
     
  10. BmacIL

    BmacIL Enginerd

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    #145 BmacIL, Dec 15, 2016
    Last edited: Dec 27, 2019
    Ride Frequency Sheet

    Updated 12/27/19

    I've compiled a list of all the linear spring options and combinations that I could see being used together (based on if they're sold in pairs or not) and uploaded it to google. Please put this one on the first page [MENTION=13598]Gibbo205[/MENTION]!

    Wheel Rate:
    Wheel rate is the effective spring rate the tire sees, based on the spring and the suspension's motion ratio. The motion ratio is the ratio of spring travel to wheel travel. On the Mustang, the front is ~1 because it's a strut, and the rear is 0.492, meaning for every 1" the tire moves up/down, the spring is compressed/released by approximately 0.5".

    Wheel Rate = Spring Rate * (MR)^2

    Ride Frequency:
    The ride frequency is the natural frequency of the body, with no damping considered. Higher = Stiffer.
    Empirically tested values by application are as follows:

    RF = 1/(2*pi) * sqrt(K/Msprung)

    0.5 - 1.2 Hz - Street-only/Passenger Cars
    1.2 - 1.7 Hz - Sporty Cars, Lower end of track-focused street cars
    1.7 - 2.2 Hz - Track-focused street cars to Low-downforce racecars
    2.3+ Hz - Racecars, HPDE/Auto-X-only street cars

    There's no cutoff of where you should be, but for the enthusiast who daily drives and occasionally tracks, 1.4-1.6 Hz is a good ballpark.

    One important aspect about ride frequency is the relative frequencies between the front and the rear. General rule of thumb is to achieve the best ride response, you want your rear ride frequency to be ~10% higher than your front. This is dependent on weight distribution, of course, and the more front-heavy, the closer to 1:1 you want. A 50/50 car would want 10% for optimum results. For our cars anywhere from 1-10% will achieve good ride response characteristics. The way to think of it is this: when you hit a bump, the body of the car hasn't settled fully before the rear hits it, so you need an appropriately high rate to manage that well.

    Ride is far from the only concern, so you may give up some of the ideal response characteristics for improved response/handling. See GT350R, for example. You will see that most of the true motorsports coilover options, track cars and autocross cars are running significantly higher front ride frequencies. This is because they are trying to achieve two things: A) quick turn-in, rapid transitional response and the geometric control from a stiff front, and B) keeping the ability to put power down on corner exit. Dampers will be used to keep the ride in check over track undulations and bumps, rather than flat ride balance.

    The reason I put all this up is that in going about deciding on spring selection, there are a few important variables to consider: Rates relative to chosen dampers, ride height drop front and rear, and relative rates if choosing something other than a set of 4 springs.

    Assumptions:
    Mass of car: 3736 lb (from what things weigh thread)
    Sprung mass: 3188 lb (from what things weigh thread)
    Weight Dist. 53% F/47% R

    https://docs.google.com/spreadsheets/d/1qExrjc7BqL7y8j1XQGotlHd9L3hT41aTpKySDTfhvCE/edit?usp=sharing Screenshot_20191227-085403_Sheets.jpg
     
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  11. DivineStrike

    DivineStrike Doomsday

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    Does ride frequency change in relation to damper setting as well?
     
  12. Rebellion

    Rebellion Well-Known Member

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    From the little I know of...no, at least not at this level of analysis. This analysis relates to the first order oscillations, dampers related to the second order.

    On a first order, I'm not really clear on the implications of the actual ratio of front/rear frequencies, just don't let it be exactly equal or 1/1 (which is pretty much impossible in real life).

    On a second order, as ride frequencies increase, it becomes less important to be super precise on the dampening being critical. Of course, you'll want it to be as close to critical as possible, but the reaction times are so short that, let's say, an 10% difference in dampening on a high ride frequency will be much less noticeable that at a low ride frequency.
     
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  13. BmacIL

    BmacIL Enginerd

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    No, it is completely independent. Damper settings need to be matched to ride frequency, though.
     
  14. Bahndvr

    Bahndvr Roushcharged

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    I didn't see it, does anyone know the spring rates(progressive or linear) of the Ford 2015-2017 Mustang Track Handling Pack?
     
  15. Niz55

    Niz55 Well-Known Member

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    looks like progressive to me. But FRPP will not release the info on the rate.
     
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