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Technical De-arching Leaf Spring Question

Discussion in 'The Hokey Ass Message Board' started by rockable, Jan 17, 2019.

  1. rockable
    Joined: Dec 21, 2009
    Posts: 2,897


    If you dearch a set of rear springs by 3", will it lower the car 3"? I have 3" lowering blocks on mt 41 Plymouth and would like to get it to ride height without them, so I need to figure,out how much to de-arch them

  2. lostone
    Joined: Oct 13, 2013
    Posts: 1,199

    from kansas

    No, they move according to how you set them and how much lead you put between each leaf.

    To "fit" springs properly is an art form. Been doing it for 40 yrs. and sadly only seen 2 sets in that time that was done properly outside of our shop.

    If done properly, the ride will be smooth and the height will be "set" for along time.

    See if you have an old school shop around and have them do it. A year from now you'll be glad you did.
    Hnstray and rockable like this.
  3. Nova Thug
    Joined: Jun 9, 2012
    Posts: 179

    Nova Thug
    from SG Vizzle

    C6DB9BB4-5596-4795-B87B-15D793D1D0E2.png I had the mono leafs de-arched 2” on my ‘64 Nova. Been about a year and a half with no issues. I put all new bushings, isolaters, and stock height shackles.. The car came with some home made longer shackles that didn’t have the right size bolts for the holes drilled into them. Also had air shocks that were too long when compressed. So I swapped in a set of KYB Gas charged units. Works good..
  4. Ya know I feel the same way about engines. Hell my dad was an automotive machinist and started building in the 30s and never built a motor as right as I did. :rolleyes:

    Good advice on finding someone who knows what they are doing though. ;)
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  5. clem
    Joined: Dec 20, 2006
    Posts: 2,851


    But if the original poster got springs with the same load ratings, same eye to eye centres, etc, but with a 3”” less arch, surely he would be able to remove his lowering blocks to give the same ride height ?
    This may be an easier alternative to finding a spring shop that is capable of doing the de-arching etc.
  6. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284


    Yes, as long as the load on them is the same.
  7. lostone
    Joined: Oct 13, 2013
    Posts: 1,199

    from kansas

    Yes, if you could find a vehicle similar to the same weight and length that has less arch.

    No, 3" doesn't equal 3". Again it comes back to number of leaves and lead put into each leaf. Example an average Chevy p.U. rear leaf takes 2-1/2" of arch to raise it less than 2", a jeep that same 2-1/2" will get you almost 2-1/4". It's the number, size and width of the spring too.

    Take the springs out and work them until you get where you want to go, now this is where the experience comes in as on yours I would have to take into account where yours sits now, how beat down they are, and how much lead is in each spring.

    If it's a say 4 spring pack I would put 3/4" lead between main and second spring, 5/8", 9/16" between next two and so on.

    Here is a pic of a set I did a couple months ago that I turned into quarter elliptical springs for my model A.

    Notice the lead and shape of the springs in the first pic, second pic is what I started with, as you can see they were broke down and actually rode like crap.

    Attached Files:

    brEad likes this.

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