SOA leaf spring problem

[Rosey]

Hi Guys,

Just doing the rear of the truck for SOA. I've hit a problem, I've just put the rear leafs on the truck with new shackles and the shackles are inverting. Not sure how this is possible, it never use to happen, this is what I have changed;
I have removed leafs (3) from the pack
Welded new shackle mounts directly below the factory ones so the new mounts are not incorporated in the chasis
Replaced my old custom shackles with standard size factory shackles

I have to jack the leaf pack to get the spring eye near the shackle, and the shackle is extended forwards as far as possible. Once shackle is bolted up and I jack any further the shackle instantly continues to invert towards the front of the truck.
I can grind off the new mount and move it forward further but I'm not really sure why I have to do this and what it will do to drive shaft length and wheel base. How far am I best to move them? would I go until the shackle is vertical? remembering the vehicle is currently on blocks with no rear axle weight on the springs.

Can anyone please help. I have some pics but not sure how to upload them... Does outerlimits have web space available or do you have to link to your own web space?

thanks Guys
I've gotta get this finished in the next day and tonight!

[Rosey]

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[Wendle]

the problem lies with that empty stubbie sitting in the pic. you need to drink victorian beer to build suspensions.

removing the leaves has just free'd the pack up and let it droop a lot more than it could before. i'd move the hanger forward. this won't effect your wheelbase at all as the front half of the spring stays the same. it'll give you a better ride, but it is also probably gonna have a lot of body roll being sprung so soft. you'll want a track bar of some sort too.

[Rosey]

don't know about the VB but your comment about the mount sounds right. Would you suggest I move them forward to the point where the shackle is vertical or some other point? Thanks Wendle

cheers
Ryan

[Wendle]

VB is cat piss. melbourne or carlton.

i wuld tack the hanger on so it sit's vertical as it is, then bolt up the axle, put wheels on it, lower the whole thing to the ground and see how it sits. then cycle the suspension and see how it is. if it's all good, weld it up. you can use this setup time to set your pinion angle before welding the perches on too.

[Rosey]

sounds like a plan Wendle, hey on the topic of pinion angle, can you brefly explain what you ideally want to achieve with uni angle. Is it right that you need some offset so your drive shaft don't shake itself to pieces? I don't really understand how i should be setting this angle.

cheers
Ryan

[grimbo]

I think you need to put the diffs back on and cycle it as Wendle said. Just having the sprinh hanging like that is not giving a good indication of how they will behave with the vehicle weight and all the components hooked up

[Screwy]

im running a similar rear spring setup to that, i am still using the standard rear chassis mounts ( through the chassis ), but intend to to as u have.

I was going to weld the new mount so that the hole for the shackle bolt is about an inch further forward then where it sits on the chassis so there is far more for the shackle to travel so as more flex can be achieved.

screwy

[Rosey]

Hey Screwy,

how did you come up with the plan of 1 inch further forward? Any plan to that idea or just a stab in the dark? I think i'll do as Wendle suggested and tack it, test it and weld it properly.

Finished the front of the truck today, its bloody massive, I'm a little worried, I didn't want to attract to much attention with the local cops... the bonnet lines up with my shoulders

[Rosey]

moved the spring mount forward about 1.5" this morning. Spring sits much better ie. doesn't invert the shackle. However my next problem is the springs are to soft. They are sitting horizontal and the shackles are maxed out with the weight of the vehicle on it. I'm in the process of adding another leaf to the pack atm. See how that goes.

cheers

[DR Frankenstine]

There is a correct measurement to use so you get the best flex.
1. Measure the spring length flattened (centre of eye to centre of eye)
2. Measure the shackle (pin to pin)
3. deduct shackle length from spring length and deduct 15mm more
4. Thats the distance you should have between your spring mounts on the chassis(centre to centre)

[Screwy]

Hey Screwy,

how did you come up with the plan of 1 inch further forward? Any plan to that idea or just a stab in the dark? I think i'll do as Wendle suggested and tack it, test it and weld it properly.

Finished the front of the truck today, its bloody massive, I'm a little worried, I didn't want to attract to much attention with the local cops... the bonnet lines up with my shoulders

I used a similar measuring technique to what DOC FRANK has said above, and it cam out to be appox that much.

The idea of spring flex is that u want the shackle to be doing most of the flexing rather than it all being in the spring.
If your shackle is on a nice big angle with the bottom of it heading towards rear of car ( rear ) then the shackle has to travel a large distance before the spring starts to flex.

I run 2 leaves and one smal flat one in the rear of mine and because i picked out a specific leave my rear springs arch up a little and my 2 inch longer shackles sit farely well now, i still have to modify my mounts as u have done above ( are currently still through the chassis ) to get that extra bit of shackle angle so that the shackle travels without the spring to maximise flex.

My rig will be finished ( minus some bist and peices that require money, like trackbar and engineers ) TOMORROW, ill take some flex up pics and post em up.

screwy

[bru21]

the problem lies with that empty stubbie sitting in the pic. you need to drink victorian beer to build suspensions.
.

that is by far the smartest thing anyone has said on this forum EVER

wendle mate you are a GOD

well thats what i would have said if you didn't maket that poor cat piss comment.

now i don't know what to think.

rosey i thought you were an extra dry man (till you met her anyway)