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Improving rear suspension ride quality

AZ XJ

NAXJA Forum User
Location
AZ
My 96 XJ is my DD and it's time to address the poor ride quality I'm experiencing from the rear. It's got a 4.5" lift that started as a Rusty's kit, and has been slowly modified to replace the junk that came with the kit. The only existing pieces are the springs and shocks. After correcting the geometry in the front suspension with drop brackets and a TNT track bar system, the front ride has improved immensely. The rear however, is terrible. It is extremely stiff, and bouncy on the street even with the overload leaf removed. The rear also sits about 1-1.5" higher than the front and I HATE that look. The only time it has ridden well since I lifted it has been when I've towed a friends Rhino a couple of times. I'm not sure what I need to do, to most effectively solve these issues. I'm still running the crap Rusty's shocks. Would upgrading to a quality shock like a 5150 or OME be enough? I'm also considering replacing the 4.5" lift leaf pack with a RE 3.5" pack and adding a longer shackle to get a flatter spring and better angles. Are these good ideas? Am I missing anything? I really never tow anything, I don't haul anything around in the back. Being my DD, ride quality is of high priority.
 
Shocks, Shocks, Shocks.... This is how you improve ride quality.....
How long have the rear springs been in?
Where are the spring clamps mounted? Closer to the center equals more flex.
A longer shackle will give more flex, but wont really reduce stiffness. And if you are looking to drop the rear by 1-1.5" and get a shackle you are going to need to find a 2-2.5" spring pack suggest OME.
 
The springs have been in for over 2 years now, so I've given up hope on them becoming any softer. The spring clamps are midway between the axle centerline and the shackle. My biggest concern right now is getting the ride to a comfortable point. If that requires replacing the rear springs then I'll address the issue of it sitting uneven by adjusting the rear lift height. If not, then I suppose I can toss in some spacers to bring the front up.
 
The Rustys shocks are Crap, upgrading might solve most of your ride issues. OME shocks are said to be about the best out there for a DD that sees light to moderate trail use.

Not sure how much changing spring will help. As I remember it Rustys are among the softest available.
 
I've read here also that Rusty's springs are some of the softest springs out there, which is what led me to believe that most of my problems with the ride are related to the shocks. What throws me off though is how incredibly stiff the rear is compared to the front. I would compare it to, when you see a fullsize truck driving down the road with springs that have way too much arch in them and it's bouncing all over the place. The rear just seems to have very little give on the street. In the dirt, it works decent at speed because of the stiffness, and flexes okay, but on dirt roads it's bone jarring.
 
My RE 3.5" springs are ridiculously stiff. I have no flex from the rear and it's fairly rough. However it seems to decent at speed in the dirt.
 
Shocks will reduce the harshness, also. What size tires are you running and what air pressure?

Tires are 32" BFG Muds, I run them at about 30psi. They are getting worn out though and I'll be stepping up to 33's when I replace them.

Shackle relocation brackets will give you a much better ride.

This was an option that I had not considered. Thanks for the info, I'll look into them.

My RE 3.5" springs are ridiculously stiff. I have no flex from the rear and it's fairly rough. However it seems to decent at speed in the dirt.

WOW. thats good to know. I suppose I assumed that they would be softer riding because of the decreased arch when compared to a 4.5" spring.
 
my xj rode stiff with kRustys 4.5" springs and stock shackles. i put mj shackles on and the ride improved drastically. with the stock shackles, the leaf spring eye would hit the back of the shackle box with a loud thunk. the longer shackles kept that from happening.

i would recommend either longer shackles, and/or shackle relocation (further back)
 
What is your shackle angle at? If its at 90* its gonna ride like crap with what ever setup you got. I have some RE 4.5 springs, I had rustys $30. shocks on their. I changed the shocks and it did help, but my shackle angle was around 90*. I did the shackle relocation bracket, It helped a lot. You can really feel the back end of the jeep articulate now when offroading! I also put 1" lift boomerange shackles on, witch did not help out at all. The shackle angle stayed the same, rode the same. It just added lift. Now the problem is that the RE 4.5 springs alone netted 6.25" of lift (never settled). Then one inch for the shackles and around 3/4" for the shackle box mod. Now my rear is at 8" witch is a lot more hight then I wanted. I put a spacer in the front and its only 6.25. I hate that look as well. They said you can pull leafs out to lower it, but then you have a chance of axle warp. I am going to get rid of this RE crap and bite the bullet and buy some deavers. I want ride height at 6.5
 
Well, I just took a look, and the shackles are sitting at about 85 degrees, so they are basically sitting vertical. Is this the key to the harsh ride? It seems, from what I'm gathering, is that a good set of shocks and the shackle relocation brackets might do the trick.
 
That will make it ride a LOT better. I went with the bilstein 5150s with the 255/70 valving and they seam to ride real nice. If had extra cash I would of gone with the 7100s or the fox shocks tho.
 
I'd say do the shocks and the relocation brackets. I'm pretty sure Rusty's shocks are hydro, which don't ride near as well as nitrogen shocks like OME's. I had a Rusty's 3" lift with AAL and the ride was stiff as hell. Swapped in some OME's and it improved drastically. Got an RE lift now and after 1.5 years, the leafs are finally starting to soften up.

The relocation brackets are probably your best bet though. Improve that shackle angle and you'll get a softer ride and more flex. It will lift you up a bit unfortunately. This is what is stopping me from getting them at the moment.
 
Had the same problem with my DD and Rusty's 6.5" kit. Was always embarrassed when I had to slow down for speed bumps.

While you do need to address the shackle angle (I put on some boomerangs), a quality shock is gonna be worth its weight in gold. Look for Craigslist specials....I found all 4 Fox Reservoirs for $400. My rig is set up for crawling, with the option of going fast, and this was the best investment I ever made. Ride quality is like NIGHT and DAY.
 
Been having internet probs so I haven't been able to check back here. Thanks to everybody for the replies. Seems like shackle relocation brackets and quality shocks are gonna be the way to go. BrianHO13 directed me to H.D. Offroad Engineering for the relocation brackets, but for reference, are there other options out there? Just wanna make sure I'm getting what will be the best setup for my application.
 
Also: 30 pounds in 32s is pretty high pressure for an XJ. I run 30x9.50s at 30 lbs and it's about right... try dropping to 28 or 26. Chalk line it to be sure - maybe BFGs need more air than my coopers - but 30 sounds high to me.
 
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