I don't know bugger all about suspension so I can't really add anything to the technical side. All I do know is that all but the main leaf are reversed in the wagon (it sits real low in the arse) and the engineer said they would need to be reset the correct way. So while it may be beneficial in race applications it may not be deemed fit for road use.

I've been looking in to having the leaves reset professionally and it doesn't seem that expensive. Plus it will pass an engineers inspection no drama's.

Could also put it down to personal preference as I hate super stiff suspension. My ute has 2.5" lowering blocks and it's bone jarring. I've almost broken teeth going over speed bumps.

Harry

Thanks for your response, at least you can provide a reasoned one without becoming near hysterical.

You are of course correct about the main leaf support as you describe it, but i am alluding to situations where the main leaf is at the bottom of the stack as a result of rearrangement & the greatest point of stress would be at the axle, or at the end of a short support leaf when only a short leaf is used under it, & of course the poor old main leaf has a much greater bending moment at the ends of these substantially shorter leaves.

Keeping in mind that many of these springs are now about 35 years old, & a great number are worn where the inter leaf pads have worn completely away & are also rusted, leaving a myriad of potential stress crack starting points, then it isn't hard to see that some home grown spring mods are potentially a disaster waiting to happen.

In stock trim, the main leaf is supported by the shorter leaves below, out to a point near the eyes & the loads borne by the unsupported section are well within the main leafs ability to do so in normal, even severe, service so 'military wrap' support does not really come into the picture here at all.

Anytime we increase the distance between the spring eye & the end of the leaf below it we increase the potential for main leaf failure at or near this point & I have seen one or two jobs that had no second leaf below it at all. In a main leaf that is designed to work like this [mono leaf] it's just fine, but our Datsuns aren't, & it's not.

This is the type of unsafe practise I have alluded to.

As to the practise of reversing a stock spring leaf, well, yes, I do understand how it works & what you say is not incorrect, however it is regarded as normal practise when designing or redesigning a leaf spring stack to have each leaf in the stack work in concert with the others, not fighting against them.

Reversing a stock spring leaf, for example the second one, is not as dramatic as the example under discussion since it is long & thin & will flex along it's whole length, but from memory the overload leaf in a Ute is short thick & quite stiff, or at least it was in my 1200 ute the way I remember it. If I am correct then this effectively locks up the relatively short portion of the spring that it covers forcing the uncovered end portions of the spring to do most of the work, particularly in rebound. Depending on the degree of arch in this leaf it could be possible to deflect this overload leaf to its neutral [at rest] shape during substantial upward movement of the axle. This naturally depends on the amount of available travel & the shape & length of the overload leaf.
If this occurs then the rebound of the spring can so easily be rapid at first [pushing the body upwards] but be arrested in this motion very quickly. If this happens, keeping in mind that the spring has suddenly changed its spring rate dramatically in the rebound direction, then I can see a situation where the wheel is pulled upwards by the inertia of the rising body causing a momentary reduction in the tractive effort of that tyre. Under adverse conditions this can be more than a little disconcerting.


The desirable situation would be either a linear spring rate or a progressive one over the full travel of the spring, not one where the spring rate is severely increased across only a portion of the spring in mid stroke.

What concerns me most in the overall big picture is a situation where some car owners, unable to afford proper maintenance or modification will be running with old & worn shocks & or tyres & combined with less than well thought out home mods, this becomes an undesirable situation, particularly when the adrenalin kicks in & the driver's prowess is demonstrated to his mates.

As for the reversed leaves in racers, well I won't argue with you as my track time doesn't begin to approach yours but I can only say that I am not personally aware of any successful racers with this upturned leaf mod & the very nature of racing would dictate other suspension mods, like very firm shocks, severely limited suspension travel & a racing surface that does not often duplicate some of the roads that we encounter all too often. These conditions would severely limit or negate any undesirable features that are much more evident in a road car.
The fact that the race car is circulating in the same direction as other track users with other [presumably] skilled drivers also minimises the risk should something go awry.

This luxury is not afforded regular road users so I put it to you that the responsibility to get it right is substantially higher for road cars remembering that other innocent road users can be the ones paying the price should it all go horribly wrong.

Sorry if this is a bit long but hey, what's a bloke to do?

now every one see that last post, yes thats exactly how you show that you do know something, thankyou L18_B110

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good thing you actually let us know that coz to be honest i wouldnt have guessed that in all my life....i would have more thought you had been hanging around a mechanic and reading many books so that you can appear to know what your on about

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my summary would have gone more like:
just coz you write long posts doesnt make you smart
just coz you didnt pay someone else to do it doesnt mean its dodgy
as long as you know what your doing to your car or are being advised by someone who knows what they are doing (ie not you mr dodge) then yes you should be fine as long as you are confident in your ability to do it right
and lastly, see i was right about performance cars using this method you knob

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the only thing holding the rear axle in the car is the main leaf, whether its "supported" by the other leafs or not. moving the leaves around does not "leave it unsupported", its already is unsupported. The only way to build in any sort of failsafe for main leaf breakage is called a "military wrap" where the 2nd leaf also wraps around the front eye. I've only ever seen or heard of them being used in very heavy duty 4WD applications.

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you don't understand the properties of a leaf spring - they will resist bending in either direction from its static location and will exert force to return to that static position. When they are combined into a pack (assuming they are all in contact) they act as one spring and will exert a force to return to its static position, so you won't get the problem you imagine, any more than you would by fiting a heavier coil in the front suspension.

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pretty much every race car with leaf springs will have a reversed leaf in their spring pack, whether its done by a professional or at home, the principle is the same.

So let me see if I understand, a long post is "dangerous'? Now I'm sure that this makes a lot of sense to, ... well, you.

You are right of course, the action of puting a load leaf upside down on the top of the spring stack will lower it two ways. As you say, by forcefully deforming the spring sownwards & by acting as a thin lowering block, but the action of the spring is now severely compromised, & the rebound action is now severely & forcefully limited.
In my view, this is potentially unsafe, but what would I know, I've just been a mechanic all my adult life & been playing with modified cars since I was 14.

Ever wonder why this method of lowering is not widely used in the performance car industry by those that actually know what they're doing? It doesn't take Einstein to understand it.

Just clarify this for me will you.
You are saying that poverty [or at least limited funds] is an acceptable reason to adopt unsafe practices & that safety in vehicle modification is only for those who can afford it? That's how it reads to me & I reject that concept out of hand.

If you cant afford to modify a primary safety element of the car correctly, properly, & safely, then don't do it at all untill you can afford to do it. Hell, that's what I have to do.
In a ridiculously extreme example it could be seen that your policy would accept the use of water in brake systems when brake fluid proves to be too expensive. [this is an 'illustration of a point', so don't get excited]

So lets summarise
I'm 'dangerous' because I write long posts.
Unsafe modifiactions to primary safety components in a vehicle is acceptable to you as long as you cant afford to do it properly.
Dodgy un-engineered home grown conversions on your car are just fine as long as the inspector is not clever enough to see them as being crook. [assuming that they are crook]

I know who'se 'dangerous' around here.

im pretty sure posting a few paragraphs that could easily be summed up in a few sentences is a DANGEROUS waste of the time of anyone reading it

did i secure the load leaf with some form of clip, yeah the same one they use in stock applications....which seems to be non existant
flatter than a stock spring pack and pushing down on it? yes the load leaf is big and straight, doesnt bend easy...makes for a good flattener
yes its inverted....other wise it wouldnt do a good job of lowering the car
im sure if you look through my photo album you will catch a glimpse of it in one of 2 pictures

a ute load leaf should be too hard for demo to find...as he has a ute

you may think that pushing one spring down with another is counterproductive....well yeah im countering one spring with another to make the first spring push up less, hence the lower ride height
it also preloads the spring and makes it stiffer

you wonder why this practice is not widley adopted, maybe its because not every one has ute load leafs lying around as you said
and im sure many budget racers use a similar method to what i have done, but im also sure that many racers would also like a bit more tuneability than a big leaf pushing on some not so big leaves, hence the paying to tune the suspention to what they need

maybe i should take my car to get a roady just to see what they say, my bet is on them not saying anything as they would have no idea that its not supposed to be there....also anyone doing a raody on my car would have far more exciting things to look at like the "dodgy" home made engine conversion diff conversion brake conversion and any other modified part of my car
someone who actually knows would say something like "anything not stock should be engineered"

im sure many people would go to a shop and be happy to hand over money, but just coz you cant do something doesnt mean every one else is the same

after typing that i really dont see how you can actually churn out all these long posts
edit: and oh my god its not even as long as your last post

Quote:Now now, don't be a cranky bum.
In what way, specifically, do you think am I dangerous &/or unsafe?

Did you secure the Ute load leaf to the spring pack with some form of clip to prevent it from twisting out of alignment or does it just sit there?
I'm presuming that it is flatter than the stock spring pack & is pushing down on it, forcing the original spring pack to flatten out. This of course dramatically increases the spring rate in the opposite direction, i.e. it prevents or severely restricts the body from rising above a certain height after the spring has compressed when passing over a bump in the road.
I imagine this would result in a very harsh ride with the rebound coming to a sudden stop half way through the normal suspension travel, meaning that under 'sporting' conditions the inertia of the rising body will momentarily tend to lift the wheels from the road.
In reality the result would most likely be a momentary reduction of tyre pressure on the road surface as it tries to lift. Now that'll be something to look forward to on a wet night when punting it hard round a tight right hander, particularly with a locker diff.

This doesn't sound to me like the action of a suspension that is safe, but perhaps there are some here who are truly knowledgable that can reassure me that it is.
Did you install the Ute load leaf right way up or inverted.
Any pictures?

A great many on this forum seem to want to simply remove spring leaves or invert one or more, or invert one & place it on top. All of these practices fall under what I termed "Quick & easy" however spare Ute load spring leaves are not commonly seen & sourcing some is not 'easy' for most people most of the time. You were fortunate to have access to some.

None the less, forcing one spring leaf [or stack] down with another one strikes me as being entirely counterproductive & I wonder why it is a practice that is not widely adopted by racers or suspension specialists as the economic benefits are plainly there for all to see. I also wonder how many successfull racers use this method.

I have no idea whether it would pass muster at rego time either. Perhaps someone who actually knows might enlighten us.

Sometimes it's necessary to utilise the services of professionals to achieve the right result, ... for example, very few will bore out their own engine with makeshift tools, it's really a job for a professional with the right equipment. As for me, ... well I'm not in a position to readily source Ute spring leaves or to do my own spring resetting, hot or cold, so I'm left with few alternatives.
I would venture to say that the vast majority of forumites are in the same position.

Now, tell me again, ... specifically, why am I dangerous or unsafe? I'm sure we would all like to know.

quick and easy and seems to be doing fine in the back of my sedan:
stock leaf pack with a ute load leaf on top, results in being a fairly decent height rear guard about half way up the tyre on a 195 50 15 and is a fair whack stiffer than stock
so in summary i put one leaf in and it got the rear end exactly how i wanted it to be

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dodgeman, your unsafe and down right dangerous....im guessing doing it the right way always involves paying someone else to do it

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There is nothing hard about lowering a Datsun, the problems all revolve around Australias obsession with "quick & easy" which usually translates to "cheap & nasty"

We are dealing with one of one of the most important elements of vehicle safety & many just want to mess with something that they obviously have no understanding of whatsoever.

You, on the other hand are to be commended as you are obviously doing your homework & learning as you go & that's something I can admire.

Simply put, for mild lowering in vehicles that are not going to see 'severe duty' then modest lowering blocks can be used but are not really the solution. My personal limit in a small Datsun would be 1-1/2" as this is something like 30 to 40% of the original suspension travel in a 1200 passenger model.

For those who want to get serious, resetting combined with an increase in spring rate is the right way to do it, everything else is unsafe & may be downright dangerous.
Once this fact is accepted, it's a simple matter to make a plan & get it done.

I'd be suprised if you had any difficult finding somebody there to reset leaves. I had this done on my B120 not long ago and most spring specialists i called could do it but the price varied a lot. In the end I went with a very long established company as I figured they would have the experience and get it right, plus they had on of the cheapest prices around. They do them cold and charged me the equivelent of about $120AU to do a pair. I know it's not directly helpful as I'm in another country but I figure of most spring places here can do it, I doubt it'll be any different there.

FWIW I have tried various methods of flipping leaves etc and the outcome has always been a dreadful ride so I wouldn't try that. Good luck with it anyway.

-Ed