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Leaf spring rates
https://www.auszookers.com/forum/viewtopic.php?f=5&t=2921		 Page 1 of 1
Author:  Damo [ Thu Sep 11, 2008 2:54 am ]
Post subject:  Leaf spring rates
I've been thinking about what guys have been doing with spring swaps lately and what that is doing to the overall handling of their vehicles both onroad and off. I've always thought that the only way to increase wheel travel is to reduce the rate (stiffness) of the springs, but i'm starting to think that may not necessarily be the case. The stiffness of the spring will definitely play a part, but I don't think it's the be all and end all. So i'd like to do a little more digging and compare the spring rates of different springs and try to get some feedback as to their handling.

On that note I measured a couple of springs I had in the shed. One is a stock rear Sierra spring, the other is a rear (I think) Hilux spring with a leaf or 2 taken out.

Sierra stock rear
Width: 50mm
Main leaf lenght: 1000mm
2nd leaf length: 765mm
3rd leaf length: 640mm
Main leaf thickness: 7.5mm
2nd leaf thickness: 6mm
3rd leaf thickness: 6mm
Arch height: 125mm

Modified Hilux rear
Width: 60mm
Main leaf lenght: 1140mm
2nd leaf length: 1140mm
3rd leaf length: 800mm
4th leaf length: 430mm
Main leaf thickness: 7mm
2nd leaf thickness: 7mm
3rd leaf thickness: 7mm
3rd leaf thickness: 7mm
Arch height: 180mm

There are some calculators on the net, i'm going to grab one of these and calculate the spring rates. If anyone has some other springs handy that they could measure please send the details and i'll add it in here. I'm really interested to see what the stock front springs are rated at.
Author:  royce [ Thu Sep 11, 2008 3:12 am ]
Post subject:  Re: Leaf spring rates
the sierra spring rate info is out there, stock the rears are waaaay lighter than fronts, hence why I always harp on about adding a leaf on RUF's

I always call spring rate a function of travel but not the be all and end all, if you are too soft I dont think it will have any negative affect on travel but too stiff may mean you cant load enough weight on to push the suspension right up to the bumpstop
of course too soft could well mean you stuff a wheel up too soon and not be able to drop a wheel down enough on the other side so you dont flex like you should

and anyone starts on about dropping bumpstops and leverage off em and shit dont bother, think about what you are saying is useful :wink:
Author:  lump_a_charcoal [ Thu Sep 11, 2008 4:22 am ]
Post subject:  Re: Leaf spring rates
My car is without bumpstops, and my springs are new and stiff - Should I be looking at fitting bump stops and removing a few leaves?
Author:  BlueSuzy [ Thu Sep 11, 2008 4:50 am ]
Post subject:  Re: Leaf spring rates
Depends on what new springs they are. If they are 2" springs, Yes, it will make it alot a smoother ride.
Author:  Hybrid [ Thu Sep 11, 2008 12:10 pm ]
Post subject:  Re: Leaf spring rates
I've got some stock fronts at home Damo and some 1 tonne BA falcon rears if your really keen. :) I've actually started thinking my fronts are too soft. its funny when you start out you think soft for articulation is the be all and end all. Now I'm starting to think differently.
Author:  Damo [ Thu Sep 11, 2008 12:34 pm ]
Post subject:  Re: Leaf spring rates
Hybrid wrote:
I've got some stock fronts at home Damo and some 1 tonne BA falcon rears if your really keen. :) I've actually started thinking my fronts are too soft. its funny when you start out you think soft for articulation is the be all and end all. Now I'm starting to think differently.


What have you got in the front of yours? They are OME rears aren't they? No extra leaves, just overloads removed?

I should be in the shed Sunday if you want to drop around!

I think what Royce said in a roundabout way is that you want the spring to be just soft enough to be able to compress it to the bump stop.
Author:  Hybrid [ Thu Sep 11, 2008 5:29 pm ]
Post subject:  Re: Leaf spring rates
Damo wrote:
What have you got in the front of yours? They are OME rears aren't they? No extra leaves, just overloads removed?

I should be in the shed Sunday if you want to drop around!

I think what Royce said in a roundabout way is that you want the spring to be just soft enough to be able to compress it to the bump stop.


Yeah OME rears with just the overload out....I think...its been a while. How many leaves do the standard medium duty 40mm OME rears have? Drivers side has an extra medium length arched leaf for lean correction. I don't think I'd have any more with enough arch to beef them up. I'll have to have a look around home and do some testing.
Author:  Damo [ Thu Sep 11, 2008 6:39 pm ]
Post subject:  Re: Leaf spring rates
Hybrid wrote:
Damo wrote:
What have you got in the front of yours? They are OME rears aren't they? No extra leaves, just overloads removed?

I should be in the shed Sunday if you want to drop around!

I think what Royce said in a roundabout way is that you want the spring to be just soft enough to be able to compress it to the bump stop.


Yeah OME rears with just the overload out....I think...its been a while. How many leaves do the standard medium duty 40mm OME rears have? Drivers side has an extra medium length arched leaf for lean correction. I don't think I'd have any more with enough arch to beef them up. I'll have to have a look around home and do some testing.


Not sure how many leaves the OME rears would have, i'm guessing 3 + overload. I've got a couple of leaves from a lifted rear pack at home, you might be able to try them? We took those out of Ben's rig to soften it up a bit, I think they are about 500mm long.
Author:  Brett [ Thu Sep 11, 2008 8:31 pm ]
Post subject:  Re: Leaf spring rates
ome med rear have 5 leafs
Author:  Hybrid [ Fri Sep 12, 2008 1:32 am ]
Post subject:  Re: Leaf spring rates
Thanks Brett. I'll have to have a look at what I've got in there. I'll prob drop round sunday Damo. I'll bring what packs I've got at home for you to have a bo peep.
Author:  Damo [ Fri Sep 12, 2008 11:23 am ]
Post subject:  Re: Leaf spring rates
Brett wrote:
ome med rear have 5 leafs


I might have to measure these as well if I can. I'm thinking they may be using slightly thinner leaves. Either that or they're pretty stiff!
Author:  Hybrid [ Fri Sep 12, 2008 1:10 pm ]
Post subject:  Re: Leaf spring rates
Damo wrote:
Brett wrote:
ome med rear have 5 leafs


I might have to measure these as well if I can. I'm thinking they may be using slightly thinner leaves. Either that or they're pretty stiff!


On my way down to rover park with a load of camping gear in my OMEs were bottoming out in the rear. They definately aren't that stiff. You can measure them on the car on sunday. I don't much feel like pulling them out hehe.
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