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Spring rate????

Discussion in 'Suspension Modifications' started by HISSMAN, Feb 22, 2007.

  1. HISSMAN

    HISSMAN The Great Bearded One Staff Member Super Moderator

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    I have a huge question, and I can't find the answer anywhere, but it is possible that I may have missed it somewhere. Does anyone know what the spring rate is for the Eibach Pro-kit springs? I know that they are progressive, but I am wanting to compare them to the stock coupe springs.



    See Post #2


    -Jeff

    Edited : Thanks Jefe!

    Rate(lb/in) Front Rear Drop(in.)
    '87 Mustang 2.3L 370 160
    '87-93 Mustang 5.0 425-530 200-300
    '93 Mustang Cobra 425-530 160
    '93 Mustang Cobra R 750-850 240-260
    '94-95 Mustang Cobra 400 160
    '95 SVT Cobra R M-5310-R58 700-850
    M-5560-R58 200-260
    '96-98 Mustang Cobra 400-505 165-265
    '99-04 Mustang V6 OEM 400 190
    '99-04 Mustang GT OEM 450 210
    2000 SVT Cobra R (Eibach) M-5310-R00 800
    M-5560-R00 750 (IRS)
    2001 SVT Cobra OE M 500 470 (IRS)
    2001 Bullitt 1R3Z-5310-CA (front) 600
    1R3Z-5560-AA (rear) 250 0.75 0.75 1R3C-5560-AA ?
    2003 Mach 1 3R3Z-5310-AA (front) 600 3R33-5310-CA, 3R33-5310-AA ?
    3R3Z-5560-AA (rear) 250 0.50 0.50 3R33-5560-BB
    2003 SVT Cobra (Conv.) OEM 500 470 (IRS)
    2003 SVT Cobra Coupe OEM 600 600 (IRS)
    BBK Progressive BBK2510 ?? ?? 1 0.8
    Dech Speeddrive 1000-1200 210-280 1.5"
    Eibach Prokit 425-530 200-300 1.50 1.50
    Eibach ProKit Convertible 460-570 170-310 1.5 1.5
    Eibach ProKit Coupe 460-570 200-250 1.50 1.50
    Eibach Racekit 700-850 200-260
    Eibach Sportline 425-630 140-295 2.00 2.00
    Ford Motorsports B M-5300-B 425-530 200-300 1.50 0.75
    Ford Motorsports C M-5300-C 650 200-300 1.50 0.75
    Ford Motorsports F M-5300-F 460-570 200-250 1.50 1.50
    Ford Motorsports G (Conv.) M-5300-G 460-570 170-310 1.50 1.50
    Ford Motorsports R M-5300-R 700-850 200-260
    Global West 800 160 1 1
    Global West Comp 1000 160 1 1
    Global West Drag 680 160 1 1
    H&R Cobra Convertible Race 750-850 770 (IRS)
    H&R Cobra Coupe 700-760 685 (IRS)
    H&R Cobra Vert Super Sport 700-760 685 (IRS)
    H&R Race 750-850 260-280 1.25 1.00
    H&R Sport 490-575 250-285 1.60 1.50
    H&R Super Race 950-1050 260-300 1.25 1.25
    H&R Super Sport Coupe 51652-77 700-760 275-300 1.75 1.60
    H&R Super Sports Vert 51658-77 700-760? 275-300? 2 1.6
    Intrax 2 2
    Jamex 450-550 170-220 1.5 1.5
    Jamex Sportsprings 425-450 180-225 1.50 1.50
    Kenny Brown 650 800 (IRS) 2 1.25
    MAC Progressives 450-520 200-230
    MRT MRT-301 650 200-250 1.25 1.25
    Progress 580 250-300 1.75 1.75
    Saleen (Eibach ProKit?) 460-570 200-250
    Roush Sport SM01-37X0-V8 1.50 0.80
    Steeda Competition 555-8240 750-850 250 1.25 1.25
    Steeda Full Comp [front] 121-4540-001 850-1050 N/A 1.50 N/A
    Steeda Sport 223-9004 650 200-250 1.25 1.25
    Suspension Tech Street 725 230
    Suspension Tech Comp 850 280
     
  2. skratpiece

    skratpiece Active Member Established Member

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  3. HISSMAN

    HISSMAN The Great Bearded One Staff Member Super Moderator

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    Thanks! Good info.

    -Jeff
     
  4. x NOODLES x

    x NOODLES x Big Hitter da LLama! Established Member

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    Damn thats good info.

    Might need to be a sticky????
     
  5. bigmoose

    bigmoose Well-Known Member Established Member

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    that only shows the SRA rates. here is the info direct from an eibach tech for the eibach springs:

    So i bought a set of eibach pro springs off here and was told they were for the 03/04 cobra, well after talking with an eibach tech i found out they are not. here is the good info i got:

    99-02*: kit# 3590.140

    Front spring #3510.301
    Front spring rate: progressive 456-571 in#

    Rear spring #3590.002
    Rear spring rate: Progressive 651-822 in#

    ----------------------------------------

    03/04: kit# 3594.140

    Front spring #?
    Front spring rate: progressive 456-571 in#

    Rear spring #?
    Rear spring rate: Progressive 536-822 in#


    He also noted that the spring lengths are different for each kit. If i installed the 99-02 kit in my 04, the front will sit ~0.5" higher than it should and the rear would sit ~1.25" higher than it should with the proper kit.

    i forgot to ask the actual spring #s for the 03/04 so if someone wants to post them that would be helpful.

    I just installed the 99/01 kit in my '04 and i think it sits perfect. the front dropped about 1/2 inch(all stock isos) and the rear about an inch(top isos out). the car sits nice and level now.
     
  6. SCT2003

    SCT2003 2012 3.7 & 1986 NOTCH Established Member

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    Anybody have the correct spring #'s(which is stamped on the springs) for the 03-04 Coupe Eibach kit? I bought some used Eibach springs because the seller said they were 03-04 Coupe springs. After installing them, the front dropped only a 1/4" while the rear only 3/4"??? If I'm not mistaken, the Pro Kit is good for a 1 to 1 1/2 inch drop???

    The spring number #'s that are stamped on my springs are:

    Front: 3510.301

    Rear: 3590.002

    They are black springs BTW...not red!!!

    :beer:


    Later...Dave
     
  7. HISSMAN

    HISSMAN The Great Bearded One Staff Member Super Moderator

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    The early Eibach springs were screwed up by eibach. They were not set up properly for the 03/04 cobra. This is a reason why I won't buy Eibachs again. I ended up tossing them because they were useless and since the back end of mine only dropped a 1/4 inch after a month I was not going to resell them due to them being almost pointless. Not sure what the new number is.

    -Jeff
     
  8. SCT2003

    SCT2003 2012 3.7 & 1986 NOTCH Established Member

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    So the spring rates for both part numbers are basically the same...the only difference is the ride height huh??? If you put the 99-02 kit(# 3590.140) on a 03-04 Cobra...it'll sit higher than the correct kit(# 3594.140)???

    My new driveway is kinda steep...if the performance is the same... maybe I'll keep the 99-02 springs???

    :shrug:

    Later...Dave
     
  9. BloodSoup

    BloodSoup New Member Established Member

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    .
     
  10. skratpiece

    skratpiece Active Member Established Member

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    Why do so many "performance springs" have such low rear spring rates? The HR Super Sports are (F) 700-760 and (R) 275-300 ???
     
  11. Ralo

    Ralo Active Member Established Member

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    To help transfer for traction?
     
  12. desert_gypsy

    desert_gypsy Headbutting the horizon Established Member

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    That's absolutely correct. The lower spring rate in the back allows more weight to transfer to the drive wheels during acceleration. Combining the low rear spring rate with easy down shocks in the rear and easy up shocks in the front will drastically improve rearward weight transfer during acceleration. Another reason for the low spring rate in the rear, could be due to a significantly higher wheel rate in the rear. Wheel rate is simply a force multiplication factor which is determined by how close to the contact patch centerline the spring acts on the control arm. Anyone who can offer any clarification on this would be greatly appreciated :)
     
  13. MrSwa

    MrSwa Member Established Member

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    I just read this same discussion over on ls1gto (per a friends request) and it might be an interesting discussion here.

    [ame=http://www.ls1gto.com/forums/showthread.php?t=350293]LS1GTO.com Forums - Maybe I'm wrong, but why do you want everything so stiff?[/ame]
     
  14. bat-stang

    bat-stang The REAL Dark Knight Established Member

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    That sounds correct to me. Wheel rate has to do with actual force exerted by the spring measured at the contact patch. On the front of our cars, with the spring in the stock location, the wheel rate is 25% of the spring rate; with a coilover setup, that wheel rate is 90% of the spring rate because the spring acts on the wheel spindle as opposed to the spring perch. This allows for a more comfortable ride due to a softer spring, but a higher wheel rate because of location. IE: wheel rate of a 350# coilover spring is like 300#; to get a 300# wheel rate out of a spring in the factory location, it would have to be a 1200# spring--with a very rough ride. I forget all of the mumbo-jumbo on the irs; new to it actually. However if I were to guess, I would say that with coilovers in the rear, the wheel rate will probably be close to that of a stock located spring due to the fact that the stock spring and the coilover shock mount are very similarly located on the lower control arm. :coolman:
     
    Last edited: Apr 10, 2010
  15. KCRN12

    KCRN12 Member Established Member

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    It's also because they don't have to support the weight of the engine. Spring rates are not in inch pounds as some people type them. It's actually pounds per inch. So if a front spring rate is 700, that means it takes 700lbs to compress the spring 1 inch. So the reduced weight of not having the engine, plus weight transfer for traction, as others have stated, are the reasons.
     
  16. Jefe

    Jefe Well-Known Member Established Member

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    You might want to edit the first post and put this in there

     
  17. HISSMAN

    HISSMAN The Great Bearded One Staff Member Super Moderator

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    Done
     
  18. jrgoffin

    jrgoffin Been around... Established Member

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    Should have added this a while ago too, makes the search for IRS springs simple:

    IRS Spring Rates:
    • 2000 Cobra R F: 800 R: 750
    • 2003/2004 Coupe F: 600 R: 600
    • 2003/2004 Vert F: 500 R: 470
    • Steeda Cobra F: 720-780 R: 650-790
    • H&R Race F: 760-850 R: 770
    • H&R Sport F: 700-760 R: 685
    • Eibach Pro-Kit F: 450-570 R: 650-820
    • Kenny Brown F: 725 R: 825
     
  19. starnsey

    starnsey Active Member Established Member

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    Was told this should be added to the list. Its nowhere else on the entire internet but got it today.

    Vogtland Cobra w/ IRS Spring Rates

    Front (variable spring rate)
    Initial - 400
    Final 742

    Rear (variable spring rate)
    Initial - 274
    Final - 713
     
  20. 99 KOBRA

    99 KOBRA Speed Racer Established Member

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    My coil over spring rates are 450/575
     

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