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.

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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.

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

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?

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.

I really like this site, and often drop in to have a read (and a chuckle sometimes!) but I find threads like this pretty frustrating. A little bit of misinformation, followed by a little bit more to back up the original statements, then tweaked & tuned to further justify, just end up being a pointless effort for the poor bloke who was trying to get some simple advice on lowering his little datto.

A few facts to consider:

1.There are many, many club & state level racecars accross this land that use various arrangments of the standard leaves to achieve the desire combination of spring rate & ride height
2. I have never ever seen one of these arrangements fail.
3. The amount of load put through these springs in competion is harsh to state the least. Huge increase in power over stock, much sticker tires, locked diffs, big brakes etc.
4. You can improve the stock assembly when doing this (if you are so inclined) by replacing the centre bolt with a high tensile item, clamping a turned spacer that very accurately locates the diff housing to the spring.
5. This repeated reference to stiffening the spring rate is also misleading. You may find that if the suspension is being reviewed as a whole, soffter rear springs, shorter shocks & a sway bar MIGHT be a better overall solution. Note MIGHT be, I am not going to presume what Demo's driving style is like so I am not going to tell him he needs stiffer springs just because he is lowering his car.
6. There is another possible benefit to lowering the car by rearranging the leaves, this would be to "over-lower" the car, thereby necessitating the extension of the rear shackles to gain back some ride height which will also help get rid of some of the in- built roll understeer in these cars.
7. Lowering blocks of any height are probably last resort. Due to the increased moment they acentuate any axle wind up. Probably OK for mild street car but not ideal.
8. Comments like "everything else is unsafe & may be downright dangerous" are just inflamatory and scaremongering and shoudn't be encouraged on this site.

In my own racecar, I started off with professionally reset spings, reversed eyes etc and actually progressed (if you can call it that) to home made spring packs that let me fiddle and tune to my hearts content.

Hopefully there is not a response that starts with "So let me see if I understand..." Pfft

Quote:Well if an engineer responsible to the government regulations said that, I wouldn't argue with it.

Has anyone ever *actually* seen a leaf spring on a 1200 break? and if so what were the conditions?

Demo, the easy way to lower is lowering blocks. It's not the best way but works fine for street cars with mild lowering. In USA, 100s of thousands of cars have used lowering blocks and I've never heard of any bad reputation about it. I've heard lots of speculation from this forum, but no actual problem reports from those who actually used them. If you want the best handling, then don't use lowering blocks.

Next easiest is to take out the credit card and wave it in front of a spring shoppe. This is not only easy, but might result in the best ride and handling combination, and you can always sue the shoppe if the springs break afterwards.

For a ute, can you just remove two of the five leafs? Coupe/sedan springs are only a 3-leaf pack. I read that in a book so it is not a statement, just a question.

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That setup is pretty stupid and im sure no serious racer would use it. Its easy to see why the engineer feels that way.
If the main leaf was flipped upside down ontop of all the other leaves, it would be a different story.

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On that note, what happens to a humans brain at your age chump?

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Its called Personality Disorder. You may have read dodgy's writings about it in the past.

I'd like to hear Rallytwit's take on the leaf spring thing, since he's had a racing 1200 for a while, and had good luck with the suspension which uses 280zx / wilwood calipers on the front and has leaf springs in the rear.

I think his car has a reversed leaf. ( I don't know how or which one ) I know nothing about these crazy leafsprings.

I've gotten the impression the leafsprings are a better setup than the 4 link in some cases.

Gotta say i totally agree with mattB110 on all his points of view,i've been punting these things in a controlled environment for longer than i care to admit.One thing i have learned along the way and are prepared to share is i have had more sucess with"soft low" rear springs and quality shocks than "hard low" rear springs on the back of any datto,this has nothing to do with ride quality,it's about weight transfer and putting power down on the ground.
Organise getting your Datto on some corner scales before adding extra leaves in the back.

Anyone hazard a guess at rear corner weights of a 1200 ute?