Sagging stock front springs?

fuse

fuse

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I'm still getting to know my recently purchased 05 Sport, and at the risk of sounding like a total noob, I'm beginning to wonder if the stock front springs might be sagging. I read here that the stock front spring height is 12". I measure my front springs at 11" from the base to top of the spring, but excluding the isolator.

I'm sort of wondering if this might have something to do with the harsh ride I'm getting, even with the RS9000XL shocks that the PO installed.

For what it's worth, the rear springs are sitting at close enough to 8" that any difference is either negligible or measurement error.

Before I jump to conclusions, though, I have some questions.

Am I measuring the springs correctly?

The one and only PO used the Jeep as a DD for 125k miles. Would it be typical to see springs sag after that many miles?

The Jeep is currently not lifted, and although I'm thinking about a moderate lift at some point in the future, that's just not in the cards right now. Assuming it would be worthwhile to replace the front springs, are the Crown, OMIX-ADA and/or Moog springs acceptable replacements for stock springs?

Also, assuming I'm replacing springs, is there any other maintenance (not upgrades!) I should do while I have the wheels off and the front axle dropped? New isolators? Leveling spacers (ok maybe one upgrade) — or are those just for show?

Anything else in that area that I should double-check for repair/replacement at 125k miles while I'm in there?
 
What stiffness setting (1-9) are your RS9000XL shocks set to, what size tires are you running, and exactly what air pressure is in those tires?
 
You measure the coil, not including isolator, flat ground and unloaded. Yes, they are probably sagging. Too bad you aren't closer, I have a set of Moogs that I used for about 2k miles I'd give you. Or if you wanna road trip to Sac :D
 
Rob5589 said:
You measure the coil, not including isolator, flat ground and unloaded. Yes, they are probably sagging. Too bad you aren't closer, I have a set of Moogs that I used for about 2k miles I'd give you. Or if you wanna road trip to Sac :D
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Drat! I was just in Sacramento for work this week.
 
Jerry Bransford said:
What stiffness setting (1-9) are your RS9000XL shocks set to, what size tires are you running, and exactly what air pressure is in those tires?
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As a mountain biker, I have some appreciation of tire selection, tire pressure and suspension setup.

So I'm on 31x10.5R15 Falken Wildpeak A/T Tires — the old models, not the newer AT/3Ws. Load range C. Set at 29psi all around. Can't say that's dialed yet, but I'll keep playing with the pressure.

And the shocks are at three clicks in from soft. I did a bracketing test on a local dirt road to get there. I have to say I was unimpressed with the range of compression adjustment and the lack of separate high/low speed compression and rebound adjustments, but the Ranchos do cost a lot less than a good mountain bike shock.
 
fuse said:
As a mountain biker, I have some appreciation of tire selection, tire pressure and suspension setup.

So I'm on 31x10.5R15 Falken Wildpeak A/T Tires — the old models, not the newer AT/3Ws. Load range C. Set at 29psi all around. Can't say that's dialed yet, but I'll keep playing with the pressure.

And the shocks are at three clicks in from soft. I did a bracketing test on a local dirt road to get there. I have to say I was unimpressed with the range of compression adjustment and the lack of separate high/low speed compression and rebound adjustments, but the Ranchos do cost a lot less than a good mountain bike shock.
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That all sounds good, I was hoping for something simple to fix like 45 psi of tire pressure and/or your shocks set to 8-9.
 
Jerry Bransford said:
That all sounds good, I was hoping for something simple to fix like 45 psi of tire pressure and/or your shocks set to 8-9.
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I was hoping for the same thing. Tires were at 35psi when I bought the Jeep, and that's the first thing I changed. Shocks were all at full soft, but you want at least some damping to control rebound.

Replacements for stock springs aren't expensive, and the swap looks like it's something I could manage. Maybe it's worth trying to see if it helps?
 
KCsTJ said:
Can you post a pic of the sagging spring?
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Here's a pic of the front spring with the measuring tape roughly in place.
IMAG0624.jpg

It was tough to get a good shot of the whole spring and still show an accurate measurement, so here's a pic of the bottom of the spring, while I was holding the top of the measuring tape against the top end of the spring.
IMAG0625.jpg

Just for the record, the only mod on the Jeep that adds some weight is a rear receiver. Stock bumpers, no armor etc.
 
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Are the shocks the right size? The little bit that I researched 9000s, it seemed like they were a long shock compared to similar options.

With the Jeep on flat ground, how much shock shaft is showing; and how much room is there between the axle pad and the steel bump stop cup?

Ignore the soft bump stop jounces and you may need to cut away the red shock boot. The boot isn't really needed.
 
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From the bump stop cup to the axle pad is a little more than 3", maybe 3.25".

The front shock part number is RS999128, which is supposedly for a TJ with 0" lift. I don't understand what you're getting at with shock length, since this shock has about the same extended and compressed length as other shocks for stock height.
 
That 3-3.25" of space ought to be your suspension up up travel. That travel is what allows the suspension to soak up the road. Knowing that your springs are sagging about an inch, your Jeep has lost an inch of being able to soak up the road. Meaning that the Jeep is less comfortable than it could be.

If the shock is bottoming out before the bump stops, then two things are happening. First, you have less than up travel than the 3-3.25" of space between the bump stop cup and pad. Meaning there is even less ability for the suspension to soak up the road. Second, your shocks are acting as the bump stop which means they could be damaged.

There are better ways to measure travels and confirm if the bump stops are correct, but measuring the exposed shock shaft is a quick and easy check for obvious problems. Rancho shock recommendations seem to run long. It is worth double checking.
 
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jjvw said:
That 3-3.25" of space ought to be your suspension up up travel. That travel is what allows the suspension to soak up the road. Knowing that your springs are sagging about an inch, your Jeep has lost an inch of being able to soak up the road. Meaning that the Jeep is less comfortable than it could be.

If the shock is bottoming out before the bump stops, then two things are happening. First, you have less than up travel than the 3-3.25" of space between the bump stop cup and pad. Meaning there is even less ability for the suspension to soak up the road. Second, your shocks are acting as the bump stop which means they could be damaged.

There are better ways to measure travels and confirm if the bump stops are correct, but measuring the exposed shock shaft is a quick and easy check for obvious problems. Rancho shock recommendations seem to run long. It is worth double checking.
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Seems like we'd need to know the stock gap between bump stop cup and pad if we were going to check the shock length. Any idea what the gap ought to be for stock height?
 
fuse said:
Seems like we'd need to know the stock gap between bump stop cup and pad if we were going to check the shock length. Any idea what the gap ought to be for stock height?
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About 4". Stock travel is around 8" and should be split evenly, or close to it. Your shocks should run close to the middle of their travel for best on road ride. If they are too long they will be running in the upper 1/3rd or so of the travel and will likely ride stiff.
 
fuse said:
Seems like we'd need to know the stock gap between bump stop cup and pad if we were going to check the shock length. Any idea what the gap ought to be for stock height?
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Stock is about 4". But it doesn't matter. If the amount of exposed shaft is less that the space between the cup and pad, then that is a problem and it is likely the problem you are describing.

Regardless, that missing inch of up travel isn't helping the ride at all.
 
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Ditch the red boots. All they do is collect debris. Once you have exposed the shock shaft, tie a small zip tie around the shaft and slide it at the base of the shock body, then go for a normal drive thru areas that you would normally drive, then you'll see how much up travel you are getting, and then will know if you're driving around on the jounce bumpers all the time, which doesn't help with ride quality. Knock those tire pressures down to about 26 psi too.
 
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Thanks, guys for all the info so far! I definitely have a much better sense of the stock suspension configuration than I did before. Maybe it will help now, but even if it doesn't, it will be useful when I start thinking about a lift kit.

As the Jeep is sitting right now, the shock is extended to 16.75". The compressed length of the shock is 13.438". That leaves about 3.3" of remaining travel before the shock bottoms out. Full travel is 7.062", so the shock is sitting with just a little less than half its travel left.

In theory, I'd hit the bump stop cup before bottoming out the shock, but it's pretty close and my measurements aren't as precise as the shock spec numbers here.

Anyway, the numbers say pretty clearly that I'm missing an inch or so of spring height.
 
bobthetj03 said:
Ditch the red boots. All they do is collect debris. Once you have exposed the shock shaft, tie a small zip tie around the shaft and slide it at the base of the shock body, then go for a normal drive thru areas that you would normally drive, then you'll see how much up travel you are getting, and then will know if you're driving around on the jounce bumpers all the time, which doesn't help with ride quality. Knock those tire pressures down to about 26 psi too.
Click to expand...

Thanks for the tire PSI suggestion. I'll give that a try. I wasn't sure how low would be too low, so I've been cautious about that.

Zip tie test is a good idea too. We do that all the time with mountain bike suspension. I'll give that a shot when I get a chance. While I'm at it, I may lift up one of the front corners and see what the shock length is like at full extension with the wheel off the ground.

For what it's worth, there is a nice clean spot on the axle pad where the jounce bumper has been hitting. You can see it clearly in the photo I took when I was measuring the gap to the bump stop cup.

IMAG0628.jpg
 
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