Can you have too flat a shackle angle?

[TWISTY]

I'm currently running some custom 4" lift leaf springs with 2" extended shackles on my 40 which came with the truck when I bought it. I'm about to order a new set of custom springs which I will be specifing the length of each leaf etc. based on my current springs.

My main goal is to get more travel, better shackle angle, and extend the wheelbase. I've also sold my 35's and looking into 36 or 37" play tyres, so up travel will stay limited to about 4" as it is now, but tube fenders up front and trimming in the rear will get what ever clearance needed.

So, with not running much up travel, can you run a flatter shackle angle then the usual 45 degrees and maximise the droop? What would be the flattest you would go?

And does a really flat shackle angle cause any handling issues? I still need to drive the 40 around during the week on 33s.

Was thinking of having them around the same angle the rears on Guts's hilux on both the front and the rear of the 40......heres a pic of his.

[CanberraMav]

They look like they would invert.

I suppose if you bumpstop accordingly they cant though.

Actually come to think of it if you hit a big enough bump they still could.

[shorty_f0rty]

when i did my rear hanger flip and put on std shackles, on compression the rear would be flat against the remaining chassis. after driving out of that position the rear end that was compressed flat remained like that on flat ground.. i could get out and push the rear end up and unhook the shackle but i wouldn't like that to happen after hitting a bump at speed.. again if you sort your bump stops so that doesnt happen you should be right...

i guess the thing you want to watch is the up travel on a near flat shackle.. so if its flat at static height and you have a bump stops to stop it flattening out you have a higher chance of hitting your bumpstops at speed over bigger bumps.

this is just my 2c based on my experience and opinions tho.

hows that for flat?

[hulsty]

On my middy upfront I run LONG springs with LOTS of shackle angle, The shackles do not invert if you use anti inversion shackles, as the spring compresses the spring comes up against the inversion bars and stops it rotating further. Approach angle is about the same as when I had 2'' lifted springs with stock shackles that were virtually straight up and down.

With this much shackle angle the spring rate is very low since it does not take much to flatten the spring/shackle completely. I'm running 8 leaves upfront to hold the car up, 3F, steel bar and winch. Though they are all 2nd hand leaves that have been worked, in total I have I reckon 2'' spring lift on a good day, and probably about 3'' of bump stop clearance. I find the front a little too soft, it bottoms out easily. Though if your using new springs that havent done years in the rear of a 60 series then into a middy you'd be right and probably only need 5-6 leaves. The steering on my car has improved from the original setup of stock shackles and 2'' leaves, though it still needs castor correction, no plates at all.

Onto the important stuff, flex, its awesome!! I reckon for a SPUA unit I can get some pretty good results. The following photos show my car with the swaybar still attached on one side, i'm not sure what is limiting it, the bushes or the swaybar or something else. I know i'm going to have problems with the front driveshaft on the cross member. At the shock absorber mounts i've got 10'' of travel, so at the wheel its probably around 14'' or so. My front guards have been majorly chopped and the inners raised, and even with my 33'' I can have them rub at the top of the guard. Lots of pics so not really dial up friendly!!

Cheers

Shackle at ride height









Open Leaf


Compressed leaf


Flatten shackle

[rockcrawler31]

i always thought you should try to match the length of the main and wrap so that at full compression your bumpstops stop the travel just before your springs go completely flat. You don't really want your springs to arch in the opposite direction to what they are set at normally.

Due to the effect of leverage you will get a more compliant ride (read - more comfortable over bumps) the more shackle angle you have, and with all other things being equal, the more shackle angle you have the lower your spring rate will be for a given set on a set of springs. You will need to consult with your spring manufacturer to let them know what you are planning and what your average axle weight will be when wheeling.

so flex up your car and work out how much longer your springs will need to be on the compression side to make the shackle sit flat without inverting the arch on the spring.

However from experience with setting up my leaf sprung troopy i found the following

1. your shackles will need to have a bar welded across the middle of them to stop them turning into a parallellogram when the car is on a side slope or at max flex.

2. At max flex, angularity between the springs and the shackles/chassis will stop flex long before the shocks or shackle length does.

3. that same angularity will flog out bushes (rubber ones particularly) faster than you can replace them. this increases the strain on the shackles to remain straight, and compromises on road handling.

4. your springs will only droop as far as their unladen set arch. you will need to get your springs set with a taller arch than you need but with a softer spring rate. I.E. if you want a 4 inch lift, get springs with a 5 or 6 inch lift arch, and softer spring rate so that it sags down to 4 inch when you put the car on them. This way they will droop properly when unladen (flexing)

hope this helps

MILO

[shorty_f0rty]

i always thought you should try to match the length of the main and wrap so that at full compression your bumpstops stop the travel just before your springs go completely flat. You don't really want your springs to arch in the opposite direction to what they are set at normally.

So this is bad?

[rockcrawler31]

i can only go on what some metallurgy guys have told me, but there is a point in spring steel where if you bend it too far, it will spring back but not as far, and with a lessened spring rate. I think it's called the plastic limit or something like that. It's the same principle where you can take a small coil spring made out of thin wire and lengthen it by pulling it out too far and then it stays slightly longer than it's original position. Do it to many times and it will eventually break or lose its tension.

It's probably better to talk to a spring manufacturer to find out exactly where this point is in a leaf spring, but bear in mind that once a leaf spring goes past completely flat it will try to get shorter again, but this time it's pulling against the shackle in line and it starts getting ugly. Other than benefiting your upwards compression measurement i can't see it being any good on any components.

[rockcrawler31]

i always thought you should try to match the length of the main and wrap so that at full compression your bumpstops stop the travel just before your springs go completely flat. You don't really want your springs to arch in the opposite direction to what they are set at normally.

So this is bad?

i note that since you have gone past completely flat, the only way for your spring to get shorter is for you shackle to come back down slightly, and making the reverse bend even worse.

[lay80n]

i can only go on what some metallurgy guys have told me, but there is a point in spring steel where if you bend it too far, it will spring back but not as far, and with a lessened spring rate. I think it's called the plastic limit or something like that. It's the same principle where you can take a small coil spring made out of thin wire and lengthen it by pulling it out too far and then it stays slightly longer than it's original position. Do it to many times and it will eventually break or lose its tension.

It's probably better to talk to a spring manufacturer to find out exactly where this point is in a leaf spring, but bear in mind that once a leaf spring goes past completely flat it will try to get shorter again, but this time it's pulling against the shackle in line and it starts getting ugly. Other than benefiting your upwards compression measurement i can't see it being any good on any components.

Search for stress Vs Strain graph on the net. Basically a metal will deform so far and return to its previous shape till it reaches its limit or proportionality, after this it will continue to deform, but will not quite return to its origional shape. If force is continued to be applied, it will reach its yeild point, and any more deformation after this is permenant. Usually once the yield point is reached the force required to continue to continue to deform the material will drop off. Eventually it will fail. Metals are usually considerd to have failed once they breach the yeild point and gone beyond their yeild point.

Layto....

Edit cause my spelling sucks today

[rockcrawler31]

thanks layto

pretty much was i was trying to say, but i've been having a bit of an extended brain fart of late after a post wedding bender.

[shorty_f0rty]

thanks guys.. not to get too far off topic.. the dude at carrolls springs reckoned my spring packs were great when they were in there to get them reset an inch or so..

i'll keep all the comments in mind.. but back on topic..

if your spring is long, and your shackle is long too, dont you increase the possibility of this happening (particularly in Twisty's application). The long spring is soft with a large arch to provide the required lift at rest and still move through the best cycle of articulation?

The higher the spring rate (harder) the less plyable and flexy the springs, the softer they are the more droop (and possibly compression) you will get.. IF your bumpstops are not setup right to reduce the amount of compression.

[rockcrawler31]

thanks guys.. not to get too far off topic.. the dude at carrolls springs reckoned my spring packs were great when they were in there to get them reset an inch or so..

i'll keep all the comments in mind.. but back on topic..

if your spring is long, and your shackle is long too, dont you increase the possibility of this happening (particularly in Twisty's application). The long spring is soft with a large arch to provide the required lift at rest and still move through the best cycle of articulation?

The higher the spring rate (harder) the less plyable and flexy the springs, the softer they are the more droop (and possibly compression) you will get.. IF your bumpstops are not setup right to reduce the amount of compression.

i think it would still come down to matching the length of the spring to the shackle. It's pretty hard to comment without seeing twisty's truck in the flesh, but i would surmise that with his extended bumpstops, and with that much arch in the spring that he will find it difficult to get his springs completely flat. with enough arch for a 4 inch lift the actual length of the spring would be a fair bit longer already and at compression to (longer than standard) bumpstops will probably still have some arch left in them.

Another problem i just thought of with longer springs is that the axle to chassis eye portion behaves like leading/trailing arms on a coil setup. Good flex would make it travel through a pretty short radius, pulling one side of the axle backwards as it droops. If you look at factory long leaf setups (i.e. 78 series toyota rear leaves) this is alleviated by having mounts that are further apart as well.

The pros are that the leaves can twist more along their length before transmitting that twist into the bushes and therefore binding up.

If i was designing a leaf spring vehicle from scratch i would have the mounts as far as practical apart, with as long as practical shackles, SOA, with the leaves in a shallow arc at level ride position.

[hulsty]

i think it would still come down to matching the length of the spring to the shackle. It's pretty hard to comment without seeing twisty's truck in the flesh, but i would surmise that with his extended bumpstops, and with that much arch in the spring that he will find it difficult to get his springs completely flat. with enough arch for a 4 inch lift the actual length of the spring would be a fair bit longer already and at compression to (longer than standard) bumpstops will probably still have some arch left in them.

Another problem i just thought of with longer springs is that the axle to chassis eye portion behaves like leading/trailing arms on a coil setup. Good flex would make it travel through a pretty short radius, pulling one side of the axle backwards as it droops. If you look at factory long leaf setups (i.e. 78 series toyota rear leaves) this is alleviated by having mounts that are further apart as well.

The pros are that the leaves can twist more along their length before transmitting that twist into the bushes and therefore binding up.

If i was designing a leaf spring vehicle from scratch i would have the mounts as far as practical apart, with as long as practical shackles, SOA, with the leaves in a shallow arc at level ride position.

I think with a arch of 4'' you would still be able to flatten the spring, mine are arched for 2'' and they very easily flatten out.

With regard to the leading/trailing arm length, I did think about moving my springs mounts for a longer spring upfront to the rear of the diff, but in the end its alot of work and I've already got plenty of flex and the shock only has ~1'' more travel before it tops out.

The rear though I think 75'' leaves and moved mount would be good, or custom leaves to flatten out properly on compression. My rears are waaay to short.

[TWISTY]

Thanks for all the info and pics so far!

After doing some drawings in autocad I think if I run with a normal 45 degree shackle I should get more then enough droop.

Heres a few pics on what I'm planning.

Front - Diff moved forward 4 inches, and spring 3 inches longer than my current ones (total length of new spring 44")


Rear - Rear shackle mount moved back 4 inch, diff moved back 5 inches, and spring 8.5" longer then my current ones. (total length of new spring 53")

[rockcrawler31]

Oh mate.

that's going to be porno!!

[WICKED]

Might need some bigger wheels but I think those blue ones will be a little small

[TWISTY]

Seems I might have jinxed myself with this thread.

Picked up my new springs on the weekend and finished installing the fronts tonight and now I have too much shackle angle.

Not sure what the fix will be yet, dont really wanna move the shackle mounts or spring hangers, so might have to get new mains made (or shorten mine if thats possible??) Will talk to Dobinsons tomo and see what they think.

Couple pics.

Old fronts and new fronts





Shackles are hard up against the bumper.

[hulsty]

Bugger! maybe you could move the rear hanger back if its not to hard? would bring your axel back though.

What buggered up with your spring lengths? they build them different to your spec or a slight mis calc

cheers

[rockcrawler31]

bummer dude

[hulsty]

Also hows your steering go with the diff that far forward? I want to move my diff forward alot but the steering arms will rub I believe.

If you dont mind what it worth for custom springs?

cheers

[Dee]

hey mate,

sucks to hear they dont fit as expected.
I had the exact same thing happen to the rear of my zuk when i was installing longer springs!

have you fully welded your spring perches or just tacked em in place? I'd say best bet would be to move these back if you've only tacked them. Even if its only 1 - 1.5" or so. You can always redrill your perches on the diff and move it foward on the spring (actually i dont know if you can do this on a 40 or not?)

I dont know if those anti-inversion shackles are stock length or extended, of if you wanna run extended shackles or not... But you'd be suprised at how much an extended shackle will change the angle when there at real sharp angles like that.
My stock shackles were hard up against my chassis rail (even with my spring perch redrilled 25mm foward, this is my rear diff btw), when i decided to have a go with "missing-link" style drop-shackles. These brought my shackle angle back to straight.
Not much longer down the track I pulled them off and swapped it for a 2" extended shackle. and this is where they sat.



^^With the spring setup this way & a 70mm eye to eye shackle, it rested up hard underneath chassis rail. Same spring setup but now with 120mm shackle. LIke i said though, not sure if your keen on extended shackles or not, so this may not be a viable option.

[shorty_f0rty]

bummer twisty.. looks like no up travel for you! ( have you had a chance to see how much droop you've got with this setup yet? for curiosities sake?

40 spring hangers are riveted to the chassis and a pain in the a$$ to remove.. at the fixed then they also have a greasable pin with a retaining bolt (usually m8 or similar), also (at least on later model 40's) the shackle pin is seated inside the hanger meaning you can't redrill the locating hole like you have done Dee.

Those shackles are extended too.. I'm not sure how you'd go with an even longer shackle.. could you custom make some up cheap to see how you go? might be an easy fix at this point. I know you can't move the front shackle hanger any further forward either on a 40..

maybe something else to try before shortening the main leaves is to add 1-2" of lift to those springs.. the arch should give you a better shackle angle and more height. there doesnt look like many leaves in the pack so you could get away with it..

keep us posted.

[Gwagensteve]

He'd have to lower the bumpstops heavily then to prevent the same thing happening though on compression.

Even longer shackles is a kinda fix, but might look a bit scary.

Steve.

[Dee]

Even longer shackles is a kinda fix, but might look a bit scary.

x2, i wasnt sure if he's current ones are extended and/or if it's something he may want to look into. Guess it comes down to personal preference, handling & approach/departure comprimise.

[RAY185]

Yeah those are already extended shackles from the look of it. Looks like you only have 2 options Dave; revised main spring length or move the rear hanger back (but this isnt desireable as your idea was to push the diff forward).

Hopefully Dobinsons can organise a replacement main spring for you without too much fuss.

[TWISTY]

Bugger! maybe you could move the rear hanger back if its not to hard? would bring your axel back though. What buggered up with your spring lengths? they build them different to your spec or a slight mis calc cheers

Yeah, I think moving the spring hanger back is going to be the easiest fix, and is what Ray at Dobinsons recomended when I spoke to him this morning. Said they can make new mains no dramas, but its at my expense since I supplied the specs (which is fair enough). Had a look this morning at the hanger, and it looks like a piece of cake to move back. Will also help give me more castor too.

As for what buggered up the spring lengths, am buggered if I know. Everything in real life measure up as I had them in autocad, yet when fitted they are too long. Must be something I'm not taking into account, but I'm not sure what.

Also hows your steering go with the diff that far forward? I want to move my diff forward alot but the steering arms will rub I believe.If you dont mind what it worth for custom springs? cheers

Since I've done a 80 series power steering coversion we set the box up to allow the diff to come about 2"-3" forward as thats all I was originally planning. Was just going to redrill and add crush tubes for the new springs, but if I move the fixed hanger back and loose some wheelbase the steering will be fine.

Price, for these $1200.....was told if it was a normal set of 2" lift springs with longer mains it would be a lot cheaper and is what my last set was.

hey mate,

sucks to hear they dont fit as expected.
I had the exact same thing happen to the rear of my zuk when i was installing longer springs!

have you fully welded your spring perches or just tacked em in place? I'd say best bet would be to move these back if you've only tacked them. Even if its only 1 - 1.5" or so. You can always redrill your perches on the diff and move it foward on the spring (actually i dont know if you can do this on a 40 or not?)

I dont know if those anti-inversion shackles are stock length or extended, of if you wanna run extended shackles or not... But you'd be suprised at how much an extended shackle will change the angle when there at real sharp angles like that.
My stock shackles were hard up against my chassis rail (even with my spring perch redrilled 25mm foward, this is my rear diff btw), when i decided to have a go with "missing-link" style drop-shackles. These brought my shackle angle back to straight.
Not much longer down the track I pulled them off and swapped it for a 2" extended shackle. and this is where they sat.

^^With the spring setup this way & a 70mm eye to eye shackle, it rested up hard underneath chassis rail. Same spring setup but now with 120mm shackle. LIke i said though, not sure if your keen on extended shackles or not, so this may not be a viable option.

As shorty_fOrty mentioned, my shackles are 2" longer then std, and definetley dont want to go any longer. With the front I was hoping to get away with using all the stock spring hangers and shackle mounts in the stock locations. So haven't tacked anything in yet as its all factory, but yeah, relocating the rear fixed mount is going to have to be the fix i think.

bummer twisty.. looks like no up travel for you! ( have you had a chance to see how much droop you've got with this setup yet? for curiosities sake?

40 spring hangers are riveted to the chassis and a pain in the a$$ to remove.. at the fixed then they also have a greasable pin with a retaining bolt (usually m8 or similar), also (at least on later model 40's) the shackle pin is seated inside the hanger meaning you can't redrill the locating hole like you have done Dee.

Those shackles are extended too.. I'm not sure how you'd go with an even longer shackle.. could you custom make some up cheap to see how you go? might be an easy fix at this point. I know you can't move the front shackle hanger any further forward either on a 40..

maybe something else to try before shortening the main leaves is to add 1-2" of lift to those springs.. the arch should give you a better shackle angle and more height. there doesnt look like many leaves in the pack so you could get away with it..

keep us posted.

Hehe, droop with this setup is bucketloads! With the chassis on stands at approx ride height I can take the 33s off and the diff will drop down to the ground and the shackle will be about vertical, so would still have some left...

Putting more arch into them would make it too high, and limit my uptravel too much. I dont really want anymore lift then what I used to have, except for maybe an extra inch in the rear.

He'd have to lower the bumpstops heavily then to prevent the same thing happening though on compression.

Even longer shackles is a kinda fix, but might look a bit scary.

Steve.

Yep, agree, dont want longer shackles then what I've got now, droop would be impressive but.



So, plan is to leave the front for now and tackle the rear on saturday. Hopefully they aren't too long too and the shackle mount doesn't end up needing to be past the rear bumper. Will be spewin then as I dont think the front fixed hangers for the rear springs are as easy to move front ones.

If all goes well in the rear, will relocate the fixed hangers back to achieve 45 degree shackle angle and run that. Will see how far they need to go back and what happens with the wheelbase, may redrill the perches to get some of it back.

Jeez i hope this is all worth it.

[MissDrew]

They look like they would invert.

I suppose if you bumpstop accordingly they cant though.

Actually come to think of it if you hit a big enough bump they still could.

Been there since 2002, never had any problems.
Since my springs are dead flat at ride height, the shackel only ever moves forward/down for both compression and droop.

Twisty, before you do anything make up a set of (tempary) longer shackels and see what it does. You`d need about 2 inches longer then what you have. It`ll cost you nothing and you can see how it`ll drive etc without spending anymore dollars.
Personaly Id use this time to do a shackel reversal and use the springs you have. Then just set the shackel mounts where you want/need them.

[TWISTY]

Twisty, before you do anything make up a set of (tempary) longer shackels and see what it does. You`d need about 2 inches longer then what you have. It`ll cost you nothing and you can see how it`ll drive etc without spending anymore dollars.
Personaly Id use this time to do a shackel reversal and use the springs you have. Then just set the shackel mounts where you want/need them.

Yeah Guts, have thought about a shackle reversal a few times, but haven't rear many good things about them on IH8Mud. A lot of people that have done them wish they didn't (but then a lot swear by it too). Main complaint from the people who didn't like it was the diving under brakes?

Shackle reversal would be a nice way to fix the problem but, and get a heap better approach angle. (Probably a good way to swap some 60 series diffs in too). Might do some more research into it.

[rockcrawler31]

Yeah those are already extended shackles from the look of it. Looks like you only have 2 options Dave; revised main spring length or move the rear hanger back (but this isnt desireable as your idea was to push the diff forward).

Hopefully Dobinsons can organise a replacement main spring for you without too much fuss.

i would have thoght that he could move the rear hanger back by two inches or so then move the axle forward on the spring by the equivalent amount. Wouldn't this give a heap better flex anyway due to the effect of having a longer distance to the fixed eye (the same effect as having longer leading arms), and therefore longer area of spring to twist before transmitting twist into the bushes and binding up.

[TWISTY]

Got the rears in over the weekend, they are a little long too. I have only flipped the std. hanger 180 degrees, and can probably move it another inch back, but dont know if that will be enough.

Am thinking the easiest way now will be to pay to have them freighted back up to Dobinsons in Rocky and have all the mains shortened 2" on the shackle side.

New Rears vs Olds


The tyres hitting the panels is stopping the rear dropping all the way down and the shackles going even flatter.


Am happy with the wheelbase but