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?