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View Full Version : Rear flex...help...and stuff...


FJBen
04-05-2007, 03:17 PM
Ok, so I know the basics for getting more flex from leaf springs...but I'm just gonna bug everyone to see if I'm missing something.

Currently SOA, stock springs, stock shackles...

Shocks are mounted on top the axle, but thats going to change, I don't think thats the limiting factor, although it's not helping.

Shackles/bushings are poo...So I'm going to change that and make some longer shackles as the rear is sitting lower than the front ~1" The slightly longer shackle should help with the flex/swing.

Opening up the "tab" or spring keepers...this should also help a little...

I don't want to mess too much with the springs, as I will be carrying people/stuff in the back, so I don't want her to squat badly from really soft springs.

You can see how the front is doing all the work, I would just like the back to do something. It's really more evident when going fowards...it lifts the rear tire VERY quickly. Backing up, forces the front to do the work.

Short of 4 linking, any other ideas?

Uncle Ben
04-05-2007, 03:30 PM
Ahhhh....buy an 80? :rolleyes: :hill:

FJBen
04-05-2007, 03:46 PM
Ahhhh....buy an 80? :rolleyes: :hill:


:lmao: Other than it had the opposite issues :D So I need to put the rear setup from the 80 on my 40...anyone know where I can find a donor 80? :D

corsair23
04-05-2007, 03:48 PM
No ideas but when did you move to CA? :)

Uncle Ben
04-05-2007, 04:00 PM
:lmao: Other than it had the opposite issues :D So I need to put the rear setup from the 80 on my 40...anyone know where I can find a donor 80? :D


Robbies is right up the street and he's gone..... shhhhh

FJBen
04-05-2007, 04:35 PM
sweeeeet! He's got the good stuff! :D

FJBen
04-05-2007, 04:35 PM
No ideas but when did you move to CA? :)


yeah...need to plate that....sooon! :D

wesintl
04-05-2007, 04:45 PM
looks about right for a stock soa.

4 link yo... http://proffittscruisers.com/suspension/coils.html

nakman
04-05-2007, 04:48 PM
Take the shocks off and test again. At least to rule them out as limiters..

farnhamstj
04-05-2007, 08:11 PM
You could take out the shortest leaf if you never load up with too much weight. I don't think it would change the ride height except for thickness of the leaf. While you got it appart. repaint and grease between all the leaves. I think what your seeing is mostly a weight issue. 2f in front, nada in rear. Put 300 lbs of crap in the bad and take another picture. Or buy a 100.

SROR/AKA 2BAD
04-05-2007, 11:26 PM
swap out to 60 rear springs and reweld the rear shackle hanger.

FJBen
04-06-2007, 08:59 AM
You could take out the shortest leaf if you never load up with too much weight. I don't think it would change the ride height except for thickness of the leaf. While you got it appart. repaint and grease between all the leaves. I think what your seeing is mostly a weight issue. 2f in front, nada in rear. Put 300 lbs of crap in the bad and take another picture. Or buy a 100.


I've got a 350 under the hood, so a little less weight :D I'm going to pull those craptastic shock as they are crappy gabrielle/knockoffs that are blown and leaking...see if that with a better shackle will help any.....

well when I buy a 100 then my front won't flex :D

MDH33
04-06-2007, 10:20 AM
I've got a 350 under the hood, so a little less weight :D I'm going to pull those craptastic shock as they are crappy gabrielle/knockoffs that are blown and leaking...see if that with a better shackle will help any.....

well when I buy a 100 then my front won't flex :D


What about longer shocks and some cantilever shackles?

http://mdhuber.smugmug.com/photos/59569712-S.jpg

Red_Chili
04-06-2007, 10:32 AM
If the thought of flopping doesn't disturb you, gopher it! They can be exciting when they unload. It does beg the question, what is the hanging down wheel actually doing for you if it bears no weight?

I've got nifty pix of a SOA CJ5, nicely built, with cantilever shackles, as it is unweighting on Spring Creek.... and suddenly rolling. Flopsiedoodle. The unweighting allows the truck to develop inertia, then when it fully extends, the truck carries the tire with the greatest of ease- right up in the air. At least an extending leaf has a gradual unweighting to it.

Generally to get more flex out of springs that can still hold up the truck, you would be talking going longer. Obviously you can't go longer behind the axle. You could install a spring hanger further forward. Alcan can fab up springs to your specification and they stand behind their products.

You can remove a leaf, but do so with care. You will stress the main leaf a bit more, and can be more likely to S-bend the leaf (evil). Obviously it can be done successfully however.

Or go 3-link... or 4-link... A little welding, a couple coils, how hard could it be??

Yeah, the lardbutt 80 is gonna flex the rear more...:lmao:

farnhamstj
04-06-2007, 10:33 AM
Hey, you wanted rear flex help, you said nothing about the front.:)

FJBen
04-06-2007, 10:58 AM
Yeah I'm not going with any wacky shackles, don't like the unloading thought :D

It appears that the 4link/3 link would be the best setup...I've heard that running Jeep TJ coils works good as they are the better suited to the weight....

I'm just to worried about the angles/geometry...love the ride/flex of coils tho. Hmmm...I could just scrap up some parts from an FJ80 :thumb:

good point farmhan!

I think my lardbutt 80 flexxed pretty good in the rear :D :thumb: (TJ's little sister modeling)

bustanutley
04-10-2007, 11:36 AM
longer springs...

http://www.imagestation.com/picture/sraid215/p275ede3a26f3e123382192372ac4baaf/ecebed16.jpg
http://home.comcast.net/~utleyz/blackonblack.JPG

FJBen
04-10-2007, 01:57 PM
longer springs...

http://www.imagestation.com/picture/sraid215/p275ede3a26f3e123382192372ac4baaf/ecebed16.jpg
http://home.comcast.net/~utleyz/blackonblack.JPG

Nice flex!


I put longer rear shackles on, slightly longer, as the factory ones don't have much swing, opened up the retainers.

On a highlift, I verified that is wasn't the shock limiting, unhooked the shock and still had like 3.5" of droop...they are pretty angled...and shot...

I'll try to do a test flex again and see where i'm at...if any better :D

i guess 4 link would be the "easy" answer....but it's not exactly cheap...


I was looking into picking up components from the 80 series rear...just triangulate the uppers...OR use 80 lowers upper and lower, triangulate the top and ditch the panhard....thoughts???

Red_Chili
04-11-2007, 08:46 AM
4link would not be nearly as easy as those nice-flexing longer leafs...
Triangling the top and going 3-link would be mighty spiffy though.

bustanutley
04-11-2007, 10:23 AM
I'm not overly impressed with most linked suspensions people just piece together. You really have to do your research and get all the geometry perfect to end up with something that works right. Most the time getting that link geometry right involves building the chassis around your suspension. I have wheeled with a lot of people that don't have their roll center high enough and there junk flops way too easy off camber. I have also wheeled with a lot of people that don't have their squat values even close to dialed and their pile hops like crazy, while my leafed rear end with proper setup on the wrap bar hooks with no hopping involved. One particular person had the proffits kit and the thing just didn't work, which is why i'm not a fan of prefabricated link geometry. Not trying to steer anyone away from getting their kit all the brackets and stuff is great but make the geometry work with your particular truck, COG wheelbase, that sort of stuff.

I would not use 80 parts all those links are way too short to start with, your roll center and anti-squat would suckÖ

FJBen
04-11-2007, 03:30 PM
I'm not overly impressed with most linked suspensions people just piece together. You really have to do your research and get all the geometry perfect to end up with something that works right. Most the time getting that link geometry right involves building the chassis around your suspension. I have wheeled with a lot of people that don't have their roll center high enough and there junk flops way too easy off camber. I have also wheeled with a lot of people that don't have their squat values even close to dialed and their pile hops like crazy, while my leafed rear end with proper setup on the wrap bar hooks with no hopping involved. One particular person had the proffits kit and the thing just didn't work, which is why i'm not a fan of prefabricated link geometry. Not trying to steer anyone away from getting their kit all the brackets and stuff is great but make the geometry work with your particular truck, COG wheelbase, that sort of stuff.

I would not use 80 parts all those links are way too short to start with, your roll center and anti-squat would suckÖ

thats the part Im' afraid of with the links. I'll get the number wrong and it will flop and wheel like crap...But in all honesty...it can't be *that* hard...I suppose if you model it "similar" to a heep rear, it should work well.

You really think the 80 rear would be all wrong??? There's a page that someone swapped the full suspenion (i wouldn't do the front) and it seems to be working real well on a 40.

I know the springs wouldn't work..but it's all basically geometry...plug it into the calculator and go correct? The lower links have to be close to 34" or in that range. if you used them top/bottom and did the geometry on the 4 link calcs....

I know the longer leaf springs would probably be the easiest. maybe using stock XJ rear springs, or dakota rears? But I don't really want to mess with flipping the rear/doing rear d-shafts right now...so that might screw me over.

Because even with the longer shackles...it still doesn't really flex for poo at the rear.

bustanutley
04-12-2007, 05:32 PM
Building a 4link is a huge can of worms. I had a system designed and ready to rock for my 40, took me months of reading to understand all the terms, know how everything worked a gather what the true general consensus was for the type of numbers you should end up with for it to work with the type of terrain you intend to wheel on and just how you want your pile to work. The hardest and most important variable you need to have before you start is the COG of your truck in the z-axis. Lots of people use the location of the top bolt on the bellhousing, but that is just a guess and to do things right there is a procedure to quantify that number. Last year I went to Moab first time since my SOA; a place full of ledges and climbs where link suspensions are supposed to be king, and my rear end worked so well I can no longer justify changing it, at least for now. I just need to pony up for shocks, right now Iím running treeroot junk yard specials, every single one mismatched. My front however gets some wrap and I need to address that.

As far as the 80 parts, Iím sure you could make it work, but I guarantee it would work better with new parts that you arenít stuck with certain parameters.

The problem you are occurring is a simple one: the springs front to rear are not the same distance from the centerline of the truck, while the springs are virtually identical (same length, same spring +/- a few leafs).
My suggestion to simply make the rear flex without changing anything is move the rear shackle mounts forward until you end up with a 45deg angle on your shackle, I guarantee that will make it work mo better.