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stock MJ leafs for offroading

J

jjvande

NAXJA Forum User
Location
Albuquerque NM 505 burque
are they up to the beating and flexing, or do they need to be upgraded?

I'm about to swap some on my XJ for more travel/lift, SOA. the front mounts will be modified for the additional length.
 
They are far to light a spring rate for the XJ in stock form. I am going to do this soon and am planning on taking a few Xj leafs and adding them in to help. I that is the plan but I dont have a stock XJ leaf pack to check lengths,arch and such though.
 
well, i got the first front mount done.

wqv4v8.jpg


wqv7nb.jpg


The spring in this pic is not in it's final location. The steel is a 3/16" thick. Plenty strong. Fully welded. BTW< please lift up carpet in the jeep before welding to the floor from the underside!

So, i measured, and these springs give me exatcly the same lift as my old ones. 4.5" rustys, with some other leafs mixed in ~~~5" of lift. with the front mount moved down about an inch (and 3" forward) and 6" boomerang shackles. im just gonna have to finish the other side and go for a drive. i fully expect to have to add/change some leafs to get it how i want it. right now, it looks like i could fit 14" travel shocks on. with the mj springs at static height (spring isnt loaded) there is still room for droop and my 10" shocks are just maxed out.
 
I don't know why the MJ springs would be too light......is this observation from personal experience? You wouldn't want the overload spring used on the XJ, but I've always thought a set of stock MJ leaves might work pretty well. They have a little more arch than the XJ leaves, and are also four leaves in the pack. I like them because they're longer.
 
T&A-XJ said:
They are far to light a spring rate for the XJ in stock form. I am going to do this soon and am planning on taking a few Xj leafs and adding them in to help. I that is the plan but I dont have a stock XJ leaf pack to check lengths,arch and such though.
Click to expand...

I beg to differ. I wish I had hard numbers. I was under the impression that MJs had a higher rate because it was a pic-up to carry stuff. It might be the same as a XJ with a real thick overload to make up for it. The overload is about 1/2". But they are not a lighter spring. I use a MJ pack under my main leaf. I use the bottom 2 XJ leafs under that. I wish I didn't need them, they are just there as spacers. All together the pack is stiffer, but not harsh. Will leave as is to have room for sag, and when I carry everything, they feel better. The MJ leaves are nice and thin. I wanted ones that would be soft and flexy. I got what I wanted. They flex good. I couldn't imagine making a similar pack with stiffer spring. That would be harsh. Since you don't have to use a XJ main leaf, the pack should feel good. I would guess you would get 4.5"-5" from that. I'm sitting at 5.5" over stock w/ mine. (oh ya, that is with a 3/4 shackle). If you need more lift, XJ leafs wouldn't help you out that much. Be more like adding blocks/spacers. You might want to consider more leafs from another SUA pack.
 
some more pictures.....

wryj9z.jpg


wrykoi.jpg


wryn35.jpg



The stock MJ leafs i picked up have three long leafs, then the ~.5" thick overload that isn't arched.
I removed the overload and replaced it with a stock xj bottom leaf...the real short one. this was to get rid of that overload sticking down,
and retain some stiffness in the region around the spring pad.
We'll see if i need to add more. I plan to get to the other side this afternoon.

Next question: what shocks will i want for the rear. I'm runnin some rs9000s in the stock locations.
I'm thinkin about moving the lower mounts up with the axle and goin through the floor with some nicer shocks.
I will figure out the lengths later, but what would a good shock be? I dont want to spend too much...maybe $300 for both.
 
Last edited:
regular MJ leafs have 3 in the pack. Metric Tonne MJ's have 4.
If the pack isn't stif enough go find a metric tonne pair.
I can't see how they wouldn't be up to the task in an XJ, I've carried A LOT of stuff in my MJ. about 1K pounds worth, no problems, springs sagged about two inches under that load.
 
I just put mj springs with the eyes cut off under my stock xj main leaf, nice ride and gave me about 7.5-8 inches over my stock height. Btw, these things are super flexy.... tucked my 33's no problem.
 
Interesting, I pulled my RE leaf pack (4.5") out and set it side by side with the MJ leafs and the difference was big. Maybe the pack I got from the JY is worn but it squated a good 4" with just me standing on it(165lbs) The RE leaf only squated 1-2".

After doing this I thought I would get a few stock XJ leafs to help with the load capacity at static height and not overy stiffen the pack. This wouldnt limit droop and keep it off the bumpstops. This is my theory anyway.

My MJ has the same pack and sagged 2" with just adding a fiberglass canopy, add my tools and such and it is resting on the bottem/overload leaf.

I may be completely wrong but isnt spring rate lbs needed to compress 1"?
 
force/unit distance deflection = spring rate

These do seem a little soft. but i'lll never know until i load it up and go for a drive. they do sit at the height i wanted them to... and should droop very far. Can someone post a picture of the metric ton MJ leafs? I want to see where the leafs are situated in the pack.
 
so the install is complete. It took me a while. the brackets were fun to make. I used a 4.5" angle grinder and some thin metal cutting wheels for everything.

The welding to the floor pan was fun. I think i will add a plate above where these mounts are on the inside and tie that into the cage when that happens.

The jeep sits perfect. 5" of lift. and the ride is AMAZING...i mean...i took it around the block and hit some speed bumps...
but i will take it out tomorrow and really give it the go. the ride is smooth and the xj feels so nice.
i am curious to see how it does in the fast stuff with the whoops and large bumps. I think i will be adding another leaf to each side,

an interesting note. the xj springs had 5 leafs....these have 4.... and the packs are the same overall thickness.

wt7vcm.jpg


is that shackle angle too much? i havn't seen what it looks like when stuffed.

wt7xcn.jpg
 
I wasn't happy with the last MJ leaf, and the short XJ overload leaf. I decided to put the second from bottom XJ leaf in. I cut the end off of one end so the leaf was evenly spaced with the othe leaf ends. I drilled all my leafs and put tip certs it. They ride great. Since you are not using the XJ main leaf to bolt to, I recommend you do the same. It isn't going to give you any lift really other than the thickness, but there will be more support for the bottom MJ leaf. No worries about bending breaking at the edge of the short XJ overload.
 
how about some pictures of the whole jeep from the side to show ride hight and see where the tire sits in the wheel well i would like to try this
 
im gonna take it into the mesa today and get some flex shots and test the ride in the bumps.

after garage flexing...the only region that scares me on the springs can be seen in that last pic, is where the main leaf contacts the next leaf...it's actually bending the main up against the retainer. i find it hard to believe this is how they were stock on an MJ, but i guess so.
 
Dirt Surfer said:
I wasn't happy with the last MJ leaf, and the short XJ overload leaf. I decided to put the second from bottom XJ leaf in. I cut the end off of one end so the leaf was evenly spaced with the othe leaf ends. I drilled all my leafs and put tip certs it. They ride great. Since you are not using the XJ main leaf to bolt to, I recommend you do the same. It isn't going to give you any lift really other than the thickness, but there will be more support for the bottom MJ leaf. No worries about bending breaking at the edge of the short XJ overload.
Click to expand...

did you use the MJ main leaf ? im confused
 
jjvande said:
did you use the MJ main leaf ? im confused
Click to expand...

I didn't change my mounts, so I had to use my XJ main leaf. I cut the eyes off the MJ main leaf and put the whole MJ pack, minus the overload leaf (3 pieces), under that. Then used the XJ short overload leaf, and the next longest leaf under all that. Bolted it up. So if you did the same thing, you would not have a XJ main leaf in there.
 
wumsec.jpg




wungar.jpg


the rear at close to full droop. this was as high as my jack stands would allow.
Pic is at 12" of droop from where the BS come in contact.

The springs behaved very nice in the rough.
Perhaps they're a little on the soft side, but with the rs9000s on a higher setting, the travel is very smooth and not bouncy.
the rear now soaks up whoops instead of springing off them.
I think the lower spring rate and increased dampening rate are a perfect combo.
But, time will tell if i need to add more leafs for all the extra stuff in the jeep.

wunhy0.jpg
 
Looks good. So you're about 5" lift with a pretty light load? This using a 6" shackle (1.5" lift) and moving the front mount down an inch (.5" lift) to get a combined 5".

I plan on using the same front mount location as you and a 5" shackle so about .5" less lift. To get mine up to 5" of lift with my weight I am guessing that an XJ main leaf or second to will be needed and possibly the XJ overload. My main concern is the rate as I can build a small block to level it out but cant have it too soft with all the weight I have on the back end.
 
arent the mj packs like 7" longer than the xj but not centered like 4" longer from center pin in the front and 3" to the back your axle looks perfectly centered the boomerangs compensate for the back so how far forward are the new mounts
 
3 inches forward and 1 inch down. I would consider this a minimum. the boomerang shackles are a little angled for my taste and are just almost in contact with the frame when fully stuffed.

Question:

THose of you running 12" to 14" travel shocks on the rear...did you have to get a special driveshaft for that much travel? im running a AA SYE and TW CV shaft. I guess i could jsut go jack it back up and check to see if it's binding. but i dont want to get new shocks until i make sure the shaft can rotate at full droop w/o binding.
 
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