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Leafspring calculator

There appears to be some useful information in their tech section too. Thanks ...

Les
 
quite interesting. i feel like a newb reading that stuff :D
 
Decent article, although a bit lacking in technical details. I disagree on the comment about tapered ends. If they make any difference at all, it is very, very slight.

I'm running Netscape 7.2 -- the calculator doesn't work for me. Does it work for you guys? If so, what browser?
 
Eagle said:
Decent article, although a bit lacking in technical details. I disagree on the comment about tapered ends. If they make any difference at all, it is very, very slight.

I'm running Netscape 7.2 -- the calculator doesn't work for me. Does it work for you guys? If so, what browser?
Click to expand...
The calculator worked for me just fine ... IE6.0

BTW, I calculated my spring rate using 52" eye to eye, .25" thick main leaf, (4) leafs, and 2.5" width ... calculated at <80 lbs/in. spring rate. I know I'm running a soft spring, but I was surprised it was that low.

Les
 
LBEXJ said:
The calculator worked for me just fine ... IE6.0

BTW, I calculated my spring rate using 52" eye to eye, .25" thick main leaf, (4) leafs, and 2.5" width ... calculated at <80 lbs/in. spring rate. I know I'm running a soft spring, but I was surprised it was that low.

Les
Click to expand...
Maybe I should be happy it doesn't work. Stock spring rate should be somewhere around 180 pounds/inch for the rears.

The formula I got from one of the magazines a few years ago comes very close, so I think it is accurate. I'd post it, but the spreadsheet I put it in is on another computer.
 
Eagle said:
Maybe I should be happy it doesn't work. Stock spring rate should be somewhere around 180 pounds/inch for the rears.

The formula I got from one of the magazines a few years ago comes very close, so I think it is accurate. I'd post it, but the spreadsheet I put it in is on another computer.
Click to expand...
I went back to the calculator ... I entered 5 leafs (omitted the main leaf the first time) and it calculated it @ 101.66 lbs/in.

I'm a bit skeptical about it because it does not take into consideration the thickness' and length/spacing of the other leafs.

Post up your chart Eagle ... I'm interested ...

Les
 
I haven't looked at the calculator but can tell you that 87 rear springs were 200 lbs (standard suspension) and the pair of springs that came on a lite duty towing package were 240 lbs. The spring rate is stamped in the bottom of the shortest leaf at its outer end behind the axle. Best seen on a lift using a wire brush!!! Being a jeep this may vary somewhat - but around 200 is probably the stock #
 
(Leaf Width in Inches x Number of Leaves)/72 x (1820 x Leaf Thickness)/Spring Length

For a 4-leaf spring 53" long and using .250 as the thickness, this formula returns a spring rate of 172 pounds per inch. Add a fifth leaf and it'll return 215 pounds per inch.
 
I didn't look closely enough at the on line calculator, but I suspect they use the same spring formula as below... This one also includes the formula for calc'ing coils springs too...

SpringCalcs.jpg
 
So how do these numbers apply to the weight of the rig, to get the correct rates. In other words, if One was to weigh the back of their rig, how do you know what rates to shoot for??
 
Calculator doesn't work for me, it gives no results. I got my results from the formula in the other post.

If around 200 lb/in is stock, I'm looking at maybe 220 lb/in with tools,gear, fullsize spare on swing out rack, etc. Does that sound about right to you guys? I'm currently at around 170 with RE 6.5 in springs. With the cantilevered weight of a 36 inch tire on the rack, it feels a little on the mushy side.
 
I guess if 180 - 200 lbs/in is stock, 220 would be a bit firmer. It should improve your ride if you think your current springs are too "mushy".

Then again, I really don't know diddly. What is worse, I cannot get Eagles formula to calculate anything near what the Spring rate is supposed to be ... I come up with 1.519 lbs/in. :dunno: Ivans posted formula results in a 115 lbs/in spring rate and, as posted earlier, the calculator resulted in 102 lbs/in.

I guess I'm better off not paying any attention to numbers, and sticking with my "butt". I started my leaf pack with a stock XJ main with thicker Dakota leafs at the top. The rear was over powering the front springs too much IMO, so I have since cut the Dakota leafs down and placed them lower in the pack ... basically it is now working more like a progressive leaf pack. Personally, I like the springs to absorb more at the top, but have enough spring rate to prevent them but bottoming out too easily.

Les
 
they look like they work pretty good too. a lot better than my aal shackle combo...my kidneys hurt
 
LBEXJ said:
Then again, I really don't know diddly. What is worse, I cannot get Eagles formula to calculate anything near what the Spring rate is supposed to be ... I come up with 1.519 lbs/in. :dunno: Ivans posted formula results in a 115 lbs/in spring rate and, as posted earlier, the calculator resulted in 102 lbs/in.
Click to expand...
I think I left out an exponential factor of 3. My formula should be the same one as Ivan's because it looks like he scanned the page from the same magazine where I saw the formula. Unfortunately, my time limit expired long since and I can't go back in to edit the formula.

Yeah -- I just checked. That whole second half of the formula I posted should be followed by a ^3 indicating to the third power.

It's much easier to read the forumla on the page Ivan scanned.
 
All I can tell you is my experience doing the Rock Lizard AAL using an extra XJ main leaf on each side. (Of course, I did it more than a year before Mr. Lizard, but he did a nice write-up so he deserves some credit for that.) I'm in Connecticut and after I finished the refurbishing of the Jeep I drove it to Montana. The ride was VERY comfortable. The ex-GF who now owns it was visiting a mutual friend here in CT this weekend and we talked about her XJ when I saw her. She is still happy with it, and has zero complaints about the ride quality. In her words, it's "just perfect."
 
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