Parabolic leaf springs

**isuzurover** · 4th April 2008, 01:05 PM

Originally Posted by Ruski73

I suspect the front is untouched. It is as stiff as a board. Can I remove leafs from front? I need new shockers too. What sort should I go for ... ??

If the front is stiff as a board I suspect you may have aftermarket springs. SWB fronts are generally not too bad unless rusty.

What shocks you go for depends on what setup you end up with. With the stock 9/10/11 leaf springs, you have lots of interleaf friction, so you will barely notice whether you have shocks fitted or not - believe me - I drove 400 km home (and 2 days of 4x4ing beforehand) with the front right shock removed (snapped the eye off offroad). Didn't notice the difference. But with fewer leaves (thick semi-elliptics, parabolics, etc) your shocks need to do much more work.

Shocks on a leafer generally only work in extension, not compression (I think they are called 2-way shocks?). Shocks for a coiller usually work in both directions (I think they are called 4-way).

I still have the original military shocks on the front (old-school monroe - when they were good!) which I had reconditioned by WW shocks in Brisbane.
On the rear I have OME Range Rover rear shocks - these are 4-way shocks. You can only fit these if you have a military chassis, otherwise they will be too long. I am not too fussed with OME quality (got them because they were very cheap), but they have done the job fine so far (on started weeping oil fairly early on).

Even when you only have a few leaves, you still have a fair bit of interleaf friction, so ANY reasonable quality shock of the CORRECT LENGTH will do the job (but if you have 1-6 leaves in each pack I would go for a coiller shock in preference).

Originally Posted by stirlsilver

This does indeed look really good!!! What forums are all about!!! isuzurover... that is fantastic information you are sharing there and I am seriously considering doing the tapering of the leaves as you suggested. They are aftermarket leaves though... I might see if I can borrow that leaf spring design manual from somewhere as I have an engineering background and see what I can come up with!

Stirling - thanks - glad people are finding this useful. I posted a long reply but the website crashed on me !!! will type it up again later when I have time.

**stirlsilver** · 5th April 2008, 04:15 PM

After reading your posts here and on outerlimits4x4 I decided that I had too many leafs in my rear packs (7mm x 8) when my car is a cab chassis with an alloy tray! Waaay oversprung. So at 9pm last night I got underneath and pulled out the 3rd leaf... took me a couple of hours to do both sides. I should have taken out the second leaf to maintain the even stepping of the individual leafs but it had the military wraps and I didn't want to pull out the bolts in the bushes.

I'm gonna have to take a good look at my suspension, pull out some leaves from the front and get them all reset a little higher and tempered and see how that all goes.

So in the current config it isn't ideal but oh my god did it soften the rear a lot, I can now compress the rear by pushing down with my weight! And I did originally want to take out two leaves but found that my centering bolt was too long!

Anyway I took a look at that Leaf spring design manual by SAE in the library, pretty comprehensive and pretty much tells you how to design the packs from the ground up! It was interesting to note that having leaves with blunt ends is the worst configuration. Chamfering is next best and then there was two other cofigurations that looked like the tips of a flat bladed screwdriver.

Anyway I'm heading out to do some offroad work tomorrow with some of the other guys on the forum, it will be interesting to see how it goes now as before it was the rear which was sorta letting me down in the articulation deparment.

Also, on the rear I have these two big rubber bump stops about 150mm long, are these after market or original items? Does anyone know? Was tempted to pull them out also but I figure I better check how close the tyre comes to making contact with the bottom of the tray (running 33" tyres) and If my shocks can compress all that way also.

**Ruski73** · 10th April 2008, 07:19 PM

The official count is 7 in each side front and 8 in each rear.

**isuzurover** · 10th April 2008, 07:37 PM

Originally Posted by Ruski73

The official count is 7 in each side front and 8 in each rear.

Which model landie?

Stirlsilver, there should be a couple of big rubber bump stops in there front and rear - would have to see a pic of yours to see if they are factory or not.

Glad youa re happy. I would never remove the 2nd leaf, it is a great safety factor in case the main leaf dies.

**stirlsilver** · 10th April 2008, 08:03 PM

I'm now actually eyeing off parabolics... $1,600, geez they are expensive... hmm maybe in a couple of months... It's always hard to justify purchase for the car that is the same or greater value than the car!

**Ruski73** · 10th April 2008, 08:41 PM

Originally Posted by isuzurover

Which model landie?

Bog standard Series 3 88"

**isuzurover** · 11th April 2008, 12:55 AM

Originally Posted by Ruski73

Bog standard Series 3 88"

Not quite. See the page from the SIII manual on p3. 9 leaf front and 11 leaf rear is factory.

Stirlsilver NOOOOOOOOOOOOOOOOOOOOO Don't do it - not now you have started with custom springs. Paras may be (a bit) more comfortable, but with custom semi elliptics you can get exactly what you want.

**JDNSW** · 11th April 2008, 05:36 AM

Originally Posted by stirlsilver

....... I should have taken out the second leaf to maintain the even stepping of the individual leafs but it had the military wraps and I didn't want to pull out the bolts in the bushes.

...........

Not quite sure why you call them military wraps - as far as I know they are standard on all leaf spring Landrovers.

John

**101 Ron** · 11th April 2008, 06:48 AM

The 101 landy has a parabolic set up from the factory and they are set up for carrying a payload.
The interesting thing is these springs work best at small defections like corrigations because of the little interleaf friction,but they dont have the off road flex of normal springs.
I personally would rework the leaf pack and reset the original leafs if they are in good nick.
If you have a ex army 2a one of the best things you can do is take a few leafs out (experiment) to reduce the spring rate as the miltiary always set the springs up for over load.
I found some landys like the stage one V8 wagons are very good from the factory.

**isuzurover** · 14th April 2008, 11:32 AM

Originally Posted by JDNSW

Not quite sure why you call them military wraps - as far as I know they are standard on all leaf spring Landrovers.

John

That is the common term for the double-wrap - because apart from LRs, that style of 2nd leaf is usually only used on military vehicles.

But you are right - all landies have them - one of the great ideas that LR had.

Ron - agree 100%

EDIT - btw - for anyone who is interested (and has a basic maths/engineering background), a simplified leaf spring rate equation is:

r = (w.n/12) * (t.1x10^3/L^3) * SF

Where:
r = spring rate (lb/in)
w = width of leaves = 2.5" for all SII/IIA/SIII
n = number of leaves
t = thickness of leaves (when spring packs have different thicknesses - need to calculate a few times for each group of leaves of the same thickness)
L = length of MAIN LEAF - eye to eye, with the main leaf completely flat (See SIII manual a page or two back for those values)
SF = stiffness factor (basically a fudge factor to get the equation to fit real results) - for square cut leaf ends SF = 1.1 - 1.3

If anyone is interested I could put this up into an XLS spread sheet/macro, so people can use it to design their own springs.

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