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Thread: Leaf sprung suspension setup tech.

  1. #1
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    12,096

    Leaf sprung suspension setup tech.

    Here is some of the most interesting leaf spring tech that I've seen. It really challenges a few ideas that are circulating out there regarding suspension setup with leaf springs.

    It is a technical clip, but if you're into leaf spring mods, you will really want to see this. I loved it.


    Cheers
    Slunnie


    ~ Discovery II "Storm" ~ ~ Series IIa 6cyl ute ~ ~ Series II V8 ute ~

  2. #2
    Join Date
    Jul 2018
    Location
    Northshore, Auckland NZ
    Posts
    10
    I'm thinking the easiest way to tweek shackle angle is to get custom length main and wrap leaves made up, and use them with leaves in your existing spring pack. Obviously this changes your axle location though. In my case this is actually helpful as it will help centre my wheels in the body, though at the price of reducing front propshaft length.

    I'd be interested in knowing if you could offset the centre pin on the main+wrap leaves, and use them with centred hole other leaves. I suppose you could also redrill the holes, or cut the ends to get a symmetrical setup.


    On my front spring packs the main+wrap leaves have the least amount of arch (ie they're flatter than the other leaves). The shortest leaves have the most arch, then in between there's maybe two different arches, but following that trend, ie longer leaves have less arch. I'd be interested to know if there's a reason for this, or if it was just by chance or ease of getting the overall pack arch.

    I think this is one of the reasons why the main+wrap leaves don't try to separate from the rest of the pack at full droop. Would having more free arch only on the main+wrap leaves be a good way to get more droop/down travel, without affecting the ride height too much? On jeeps etc their packs fan out quite a bit when drooping.

  3. #3
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    12,096
    I guess if you were having springs made, you would get the rest of the pack made to suit. Having an offset bolt isn't a problem, although LR didn't do it, a lot of other manufacturers do it. I've done a fair bit of research into running different springs into my Landy, and Toyota ones look like they could be suitable with some work, these having also offset centre bolts.

    Some good points, I suspect you're right that by having free main springs you will increase the droop, and I suspect the camber and retaining on the other springs relates to how they progressively activate or deactivate.
    Cheers
    Slunnie


    ~ Discovery II "Storm" ~ ~ Series IIa 6cyl ute ~ ~ Series II V8 ute ~

  4. #4
    Join Date
    Jul 2018
    Location
    Northshore, Auckland NZ
    Posts
    10
    I was hoping it would be quite cheap to have just main and wrap leaves made, rather than a full pack. Waiting on the end of the lockdown to find out (everywhere shut here in nz). I think leafspring shops make their own leaves to a book spec rather than having off the shelf specific springs, so it should be easy enough to ask for a different length, offset centre, different thickness or different arch.

    I got new springs all round a year or two ago, but have now realised the front springs were way too stiff, and also a poor up/down travel split. I've sorted the stiffness by removing leaves, and diamond cutting the ends of the leaves I've kept, as per an old thread on this forum. Just need to get main/wraps about 70mm longer to sort the shackle angle.

    The last problem will be getting more down travel. How much free arch can you put in the short landy front springs? In that old thread old mate mentions 200mm and 250mm of arch which seems a lot. If I'm 135/160 at the moment that's quite a big increase. The shackles sitting flatter would counter some of the lift (they're verticalat the moment), but probably not enough.

    Modifying the chassis to fit longer springs is meant to be the only way to get good flex up front, but I don't want to go through a cert (inspection).

  5. #5
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    12,096
    Have you looked at the longer military shackles? I'm not sure if they will help though with your setup.
    Cheers
    Slunnie


    ~ Discovery II "Storm" ~ ~ Series IIa 6cyl ute ~ ~ Series II V8 ute ~

  6. #6
    Join Date
    Jul 2018
    Location
    Northshore, Auckland NZ
    Posts
    10
    20200419_151711.jpg
    The truck has been modified a fair bit by previous owners, I'm still sussing out what bits aren't standard 2.5yrs after buying it. The shackles are military length, but appear homemade with a welded brace rather than the extra central bolt on the genuine ones. The spring hangers are also longer, presumably similar length to military chassis but without 2 sets of holes. The shocks are swb rears, which are 100mm longer extended length than stock military fronts. Even after softening the spring packs I still have loads more up travel than down, so im sitting higher than stock military setup I guess.

    The springs were 12leaf, so I replaced them with the same thinking I needed the extra leaf due to the heavier Toyota engine and gearbox. However this was a mistake it seems.
    Once I sort the spring packs I'm going to lower the bump stops as it's almost impossible to contact them at the moment, and also fit slightly longer shocks. With 12leaf packs it wasn't possible to get anywhere near the bumpstops, I've bounced both front tyres off the ground on an aggressive hill climb and still not contacted them.

  7. #7
    Join Date
    Dec 2006
    Location
    Harper Creek
    Posts
    3,370
    Thanks for the link Simon

    Iíve only played spring engineer with leaf packs on trailers.
    So, the reality is you want soft spring rate and details like ďhandingĒ are irrelevant.

    When I first started out I saw that diagram on the interwebs that shows an obtuse shackle angle being softer than an acute... that made no sense to me from a physics point of view so i had a play (not as sexy mockup as YouTube oldmate) but it took all of 5minutes to realise that diagram is arse about.

    Anyways, having played the game a few times
    To make a 1T ish trailer ride as soft as coils or air (yes Iíve done those as well)

    Take a 78/79 series rear pack With leaves removed and running a 45* shackle angle at ride height is a great setup

    You will definitely need dampers. And the packs are looooong so not all trailer chassis can package them
    But for a bullet proof soft setup itís hard to beat

    Steve
    '95 130 dual cab fender (gone to a better universe)
    '10 130 dual cab fender (getting to know it's neurons)

  8. #8
    Join Date
    Jul 2018
    Location
    Northshore, Auckland NZ
    Posts
    10
    I posted a reply, but does it take a while to show up because I attached an image?

    I've got military shackles and extended spring hangers. I'm not trying to pursue crazy flex, but might as well try and make the suspension work as well as it can within reason.

  9. #9
    Join Date
    Jul 2018
    Location
    Northshore, Auckland NZ
    Posts
    10
    Well I got my leaves. The local spring shop didn't want a bar of it, so I used a spring shop from another city who I bought my spring packs from previously. They were pretty adamant that the longer leaves should have less arch so the pack would stay together, but agreed to make the leaves I wanted anyway.

    I cut the welded braces out my shackles, and got main/wraps that just clear the chassis when flat. I went with 190/180mm arch rhs/lhs. This is about 30/50mm more than the previous spring pack arch, but a bit more again than the previous main/wraps. We offset the centre hole on the new leaves so the axle is only moved 20mm back from stock.

    The new leaves seem to work nicely. I get an extra 50mm down travel at the shocks, ride height is roughly the same, perhaps 10mm higher than before, but I think the extra arch added slightly more than this but was balanced out by the flatter shackle angle. The new shackle angle would have to be close to 45deg at rest. The leaves don't pull the shackles in to vertical at full droop, so I probably could have gone with more free arch but this would probably then raise ride height excessively.
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    1975 S3 Ute with Toyota 13bt, H55f + transfer, Holset he221w turbo.

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