Thread: Leaf sprung suspension setup tech.

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.

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.

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).

Have you looked at the longer military shackles? I'm not sure if they will help though with your setup.

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.

Thanks for the link Simon

I’ve only played spring engineer with leaf packs on trailers.
So, the reality is you want soft spring rate and details like “handing” 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 I’ve 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 it’s hard to beat

Steve

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.