perpetual

So I've been driving my 96 most of the winter now. I've got new 31x10.5 Goodyear Duratracs on it, as well as a ~3" lift with new Pro-Comp leafs and Pro-Comp coils up front. For shocks I have Skyjacker Hydro 7000s on all the corners.

I'm not expecting this thing to ride like a Lexus, but holy cow there's stretches of road around here that I drive on daily that almost shake my teeth loose. When the road is smooth, it rides really nice. There's an offramp that I use to get to work that is frequented by a lot of cement trucks, so it's really rough. The Jeep just pounds through that stretch and it's really uncomfortable. When it's REALLY cold out it's worse (like below zero) which I expect to a point because the shocks probably just don't move as quick.

Here's my question. Is it the coils/leafs that's causing most of the jarring, or are the shocks more responsible. I assume it's a combination between the two, but changing out the shocks is a far easier option than the other parts. I was hoping that perhaps since the XJs are so light that the Skyjackers are just too much shock for them.

Any suggestions?

caged

bilsteins.

but it's possible your bushings are shot. check your control arm bushings including the upper control arm axle bushings.

perpetual

I will check the bushings if it ever gets warm enough out to crawl around under the thing. Doesn't seem to be any clunking around, just bouncing like a shopping cart.

Tsaani97xj

I have been chasing this as well. After a lot of reading, thinking and driving I am pretty sure I get it. I have always been interested in suspensions since a couple decades ago and it started with rc cars. I remember my first one with a basic spring suspension with no shocks and it handled horribly. Then progressing in the hobby and experiencing more advanced cars that you could drop from several feet in the air and they would land almost like a pillow. You can also see this tech in off-road race trucks/buggies and now modern monster trucks for an example.

What it comes down to is the suspension's ability to compress under load or force and it's ability to control and regulate this. Our XJs come with coils with a spring rate of about 140-150 lbs/in meaning it takes that amount of force to compress them one inch. I am not aware of a rating or measurement for shocks. A lot of lift springs (talking front springs) are over 200 lbs/in and even as high as 240 such as BDS and Zone (same springs maybe?). Now if you don't add weight to the vehicle like a winch, armor, recovery points etc there isn't enough force to effectively compress and cycle the suspension under normal road and driving conditions. Now add stiff fast reacting shocks, like cheap nitro charged shocks, and you increase the amount of force needed to compress and cycle the suspension. So it is a combination of both spring rate and shock dampening that will affect how your vehicle handles different terrain. Keep in mind if your spring rate is too high for the weight of the vehicle no shock is going to fix this.

The higher spring rate coils will however handle much harsher bumps and weight without bottoming out (fully compressing) then lower ones.

You can also factor in the geometry of your suspension such as control arm angles, shackle angle etc as these are what the suspension uses to apply force in a specific direction. This is why long arms perform much better than short arms because they will usually have a better angle and add a greater leverage factor to the suspension. The same springs used in a long arm suspension will perform much differently than if used in a short arm. Control arm drop brackets help by allowing force to more accurately be applied to the springs and shocks but due to the shorter length of the control arms there is only about the same leverage as a stock suspension.

Bushings factor into this a little as well since they absorb some of the energy or transfer it based on their composition/material they are made of.

I don't, unfortunately, have a formula or the math to calculate what a given spring rate should be but if you are at stock weight and want close to stock handling it only makes sense you want close to stock rates. I am sure there isn't a complete perfect setup for all applications but as with everything it is all about balancing your needs.

Tire composition, size and air pressure plays into all this as well.

I am really posting this for myself as well as the OP. It is my current understanding of all this and I have been wanting to get this out of my head. I hope it helps someone. My apologies if this went too far out of the OPs intent and for the length.

perpetual

No need to apologize as it's all useful information.

I have a gut feeling that the coils and the leafs are my main culprit. The leafs had more arch than the stock ones, which was too be expected for the lift. The front springs on the other hand were the same length as the stock ones, but they were beefier. I was actually a little surprised by that and it led me to believe that they were going to take more force to compress which probably leads to a rougher ride.

One experiment that I contemplated doing was taking the shocks out and dtiving it around my neighborhood just to see if the coils/leafs were the culprit.

Here's a picture that I took when I was installing stuff of the old and new springs/leafs

cruiser54

What tire pressure are you running?

Over 30 and they ride harsh as all get-out.

perpetual

The last time I checked they were around 30, perhaps I'll drop them down a couple pounds and see how it is. I think when I was reading a nice user-review of the Duratracs he was running them around 26/28 but it wasn't on an XJ, I think it was a Tundra. Might just take some experimentation to dial it in. I wonder what pressure is too low and would impact tire life?

cruiser54

Stock little tires were recommended to be set at 30. Try 28. Can't hurt.

95Cherokee

I notice mine rides better when I have 4 people inside, compresses the suspension easier I guess.

Probably the only way an XJ is going to ride good is to put thin side walled car tires on it and run them at low pressure, I'm not doing that though.

Tsaani97xj

So this post and the nice weather here motivated me to go out and mess with my heep. I have read quite a few people ditch their sway bar and seem to be satisfied with how it handles. I figured it wasn't much to remove so why not give it a shot. I already know my springs are way to stiff for my application so it seemed reasonable.

***DISCLAIMER***

Not having a sway bar can make your vehicle unsafe. Do this at your own risk.

*** DISCLAIMER***

Well after removing it and driving for 25-30 miles on the highway all I can say is what a difference in ride quality. For the better. I had not considered how this part played into how the suspension feels. It feels different now but not unsafe. I could imagine in a higher speed maneuver there could be issues but I am confident I am safe for now. I intend to get some soft springs and put it back on and I am betting it will be a much better combo then having it off. You can add it to the list of contributing factors in making your ride stiff. I also tried some flexing and as I guessed my front end is way to stiff and didn't compress very much at all. Also found out my rear leaf bushings are shot but that is another story.

Goodluck to all out there chasing a softer ride.

black label

It most certainly can hurt.

Remember the explorer/Firestone rollover controversy? Many believe Half the problem was fords recommendation of 26 psi that led the the tread separation.

Lowering tire pressures for low speed off roading is one thing, doing it to improve ride comfort on road is dangerous.

cruiser54

Different animal altogether. Apples to oranges. ****ty Firestone tires, undersized AND under inflated.

black label

Any tire that is under inflated causes the sidewall to come into contact with the road. The sidewall is the thinnest part of the tire and isn't designed to be driven on. By driving on it at speed you will heat up the sidewall and wear through it, then comes re blow out, then comes the roll over.

Driving on under inflated tires is bad advice for on road driving.

cruiser54

A 31" tire at 28 PSI isn't under inflated. My wife's 88 has that set-up. A chalk test verifies this much more than a frickin drama queen crying wolf, especially one who obviously has very little real-life automotive experience. Knock it off.

salad

Sidewall touching the road? You're going to pop a bead long before sidewalls touch. Maybe if they're made of paper and you deflate to 3 PSI. +/- 10 PSI isn't going to make a difference aside from ride quality and fuel economy. Have you ever worked with tires before?

The Firestone/Exploder thing was a unique combination of fail. 31s like Duratrac on an XJ are going to take a lot of effort to break. My crappy CHINA brand tires I got for free (probably retail for $40 each) will happily run at 25 PSI, loaded up with junk. Only thing that is affected is my wallet.