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LEAF SPRING RATES

Discussion in 'The Garage' started by TONYP, Aug 13, 2003.

  1. TONYP

    TONYP 1/2 ton status

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    Just got off the phone with Macsprings comp. and got the info on my new leaf springs...
    stock springs (72) 540lbs. 3 springs no lift...
    new springs 800lbs. 7 springs 6"inch lift...
    right now I have 4" lift and not sure if its the stock leaf just flipped and a 2" block to get to 4" inch, so not sure what the lbs. is but it is a little stiff up front. the mac guy told me if I remove the 2nd leaf it will drop the lbs to 610 lbs...what are you guys running on lbs.? /forums/images/graemlins/thumb.gif
     
  2. DesertDueler

    DesertDueler 1/2 ton status

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    Make and Model
    Suspension Manufacturer
    Spring Rate (Lbs/In)
    Number of Leaves
    Free Arch

    73-91 Blazer/Jimmy
    Pro Comp (11411) 520 5 3.72
    Rancho Suspension (RS86206) 520 5 3.72
    Rough Country (8002) 604 5 3.48
    Skyjacker (C140S) 490 5 5.00
    Superlift "H.D." (01-234) 605 6 4.125
    Superlift "Superride" (01-234-6) 560 5 4.375
    Tuff Country "H.D." (TCI-C4HD) 395 4 4.75
    Tuff Country "EZ-Ride" (TCI-C4M) 295 3 5.75
    Warn "standard" (721013) 672 5 4.75
    Warn "E-Z Ride" (721014) 490 2 5.00
     
  3. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    about 1/3rd of that. ouch.
     
  4. TONYP

    TONYP 1/2 ton status

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    Make and Model= <font color="blue"> 72 K5 </font>
    Suspension Manufacturer= <font color="blue"> McCallster Spring(they make the leafs for most major guys...fabtec, Ranco etc.)...</font>

    Spring Rate (Lbs/In)= <font color="blue">800lbs-remove number 2 leaf so there is only 6= 610lbs... </font>
    Number of Leaves= <font color="blue">7 </font>
    Free Arch= <font color="blue">need to check but lift is 6"inch </font>
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    So they make lift springs for Dump trucks? /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif

    I thought my Rancho's were stiff...

    Rene
     
  6. yunit

    yunit 1/2 ton status

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    My Alcan's are 260lbs in the front and 220lbs in the rear.
     
  7. Waxer

    Waxer 1/2 ton status Author

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    Those sound stiff as hell Tony. I'm running the Tuff Country EZ rides with 295 lbs/in spring rate. I like them pretty much, they seem to be nice and soft and somewhat flexy.
     
  8. TONYP

    TONYP 1/2 ton status

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    the stock springs with reversed arch are 540 lbs. remember the first gens are shorter then the second gen leaf pack..so I think most front springs will be rated higher... /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     
  9. TONYP

    TONYP 1/2 ton status

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    just checked Tuff Country...
    72 K5 6" lift 495lbs.
    73 and up 6" lift 495lbs. 4"lift is 325lbs.
     
  10. TONYP

    TONYP 1/2 ton status

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    need more info.... /forums/images/graemlins/thumb.gif
     
  11. Triaged

    Triaged 1/2 ton status

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    The reason that GM made our trucks with stiffer springs is because there was no sway bar up front. I don't know that I would want to drive a truck with sub-300 lb/in springs in the front and now sway-bar.

    My rancho springs in the front are 720 lb/in. My stock rear springs are about 225 lb/in. It makes the truck handle like crap because the back end will move and the front won't.

    From the factory all trucks are built with more roll stiffness in the front than the rear. Because the front springs are more inboard than the rear they would have to be stiffer than the rear to even have the same roll stiffness as the rear. When they put in the sway-bar they also softened up the springs to make it ride better and also handle the turns.

    If I was you I would go the same path the General went. Swap in a sway-bar. Than toss in a spring in the 300-400 lb/in range.
     
  12. TONYP

    TONYP 1/2 ton status

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    thats the answer I was looking for...everywhere I looked the 72 truck leafs were stiffer, and the no sway bar is why...heres a pic of the stiffer leafs and they seem to work...now the back need help and I have 57's ready to go on...

    [​IMG]
     
  13. GreyZuk

    GreyZuk Registered Member

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    sorry if i'm dredging up a dead post, but I have a set of 4" lift, 2.5" wide, 6 leaf, .25" thick main leaf, 48" long springs for the front of my Blazer, They only had a faded "made in Japan" on the springs, but when I run the numbers I get 180lb spring rate springs which sounds way way low than the 300-500 rate that others are posting.... Am I doing something wrong? I weigh 180 and when I stand on them they definitely dont droop noticeably
     
  14. 1977k5

    1977k5 3/4 ton status Vendor

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    How are you calculating the rate?

    Spring rate numbers from lift kit companies are totally random and I wouldn't trust them at all, there is no convention for how (or if) it's measured.

    The first inch of compression from free arch takes less weight than an inch of compression at ride height and less still than it will at full compression, leaf springs have a progressive spring rate so where you measure it matters a lot.
     
  15. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    From a CK5 post back in 2008:

    Some more math..........

    From one of the Excel spreadsheets on Pirate (by Triaged):

    R = ((2+(N'/N))*(E)*N*W*(T^3))/(6*(L/2)^3)

    R = Rate (lbs/in)
    N = number of leaves
    N' = number of full length leaves (usually 1)
    E = Modulus of Elasticity in Tension (about 30,000,000psi for most steels)
    T = Thickness of one leaf
    L = Length of the main leaf

    Using that equation and my 52" spring gives a rate of 234.2 lbs/in

    It looks like the other equation on Pirate boils down to the same thing.



    -G
     
  16. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Here's another one. What a surprise....I created a spreadsheet for something K5 related!!! :D


    [​IMG]



    -G
     
  17. GreyZuk

    GreyZuk Registered Member

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    Greg, my springs fall perfectly on your scale
    .250 main spring
    This could be what is throwing me, I'm eyeballing the springs with a cheap tape measure, not a calibrated micrometer. They could be closer to .300
    2.500" width
    48" long
    6 leafs in pack with tapered end cuts.

    177lb
     
  18. Doppler

    Doppler 1 ton status

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    That's a nice scale...but what about a 3 leaf pack? Aren't a lot of front springs 3 leaf?
     

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