Rockjock spring heights

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cmitcham

TJ Enthusiast
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southern indiana
2005 ljr. bought new 35" tires and decided to replace ome 2.5" plus spacers with real 4" springs/shocks. went with ce9131rh3/rs55256 in rear, ce9132fp/rs55255 in front. installed the rears and they seem way too tall. i have at most a quarter inch available downtravel before the shock is extended :) sure hope i've overlooked something stupid, and these will work as i expected. does anyone see something off?

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cmitcham said:
2005 ljr. bought new 35" tires and decided to replace ome 2.5" plus spacers with real 4" springs/shocks. went with ce9131rh3/rs55256 in rear, ce9132fp/rs55255 in front. installed the rears and they seem way too tall. i have at most a quarter inch available downtravel before the shock is extended :) sure hope i've overlooked something stupid, and these will work as i expected. does anyone see something off?

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You missed in their item description, those springs are 4" of lift PER SPRING, so 8" total! 🤔

Lots of companies like to throw heavier rear springs at an LJ even though the longer wheelbase shifts the weight distribution to the front. I guess they assume people only buy LJs so they can carry 800lbs of gear everywhere they go. Is there a return policy? You might be better served by the RH2 or even the RH1.

This is precisely why I'm still running my unknown brand rear springs with Rockjock fronts, because I see posts like this fairly regularly. My rears are too short but they're close enough to be better than what you're dealing with.
 
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the rear shock in the pic is fully extended at 24.67" (per rancho website, i didn't measure before install)

are the stock spring heights of 12" front 8"rear for a tj the same for lj???

thanks all!
 
cmitcham said:
the rear shock in the pic is fully extended at 24.67" (per rancho website, i didn't measure before install)

are the stock spring heights of 12" front 8"rear for a tj the same for lj???

thanks all!
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Yes, spring heights are the same.

I have same shocks front and rear and they are close to half extended at ride height at both axles.
 
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Mike_H said:
I would guess something is bound up and not letting the rear of the jeep settle. Do you have factory control arms or any other arm with a bonded bushing?
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Good thing to check. Anything with a clevite type bushing where the inner and outer sleeves are bonded to the rubber needs to be left loose until on the ground. I also roll the Jeep back and forth a few feet and bounce my weight on the bumper a few times first.
 
cmitcham said:
2005 ljr. bought new 35" tires and decided to replace ome 2.5" plus spacers with real 4" springs/shocks. went with ce9131rh3/rs55256 in rear, ce9132fp/rs55255 in front. installed the rears and they seem way too tall. i have at most a quarter inch available downtravel before the shock is extended :) sure hope i've overlooked something stupid, and these will work as i expected. does anyone see something off?

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First, I can’t tell much from how you measured the spring length because you put the tape measure inside the spring. Measure the outside from top to bottom.

Second, you only installed the rear. Now the nose is down and that allows the rear shocks to extend longer than normal under load. Finish by installing the front.
 
freedom_in_4low said:
Lots of companies like to throw heavier rear springs at an LJ even though the longer wheelbase shifts the weight distribution to the front.
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I'm the first to admit that I'm easily confused by complex engineering answers so I need some help on that one.

If everything between the same year and equipment level TJ and TJ Unlimited is the same from the rear of the belly skid forward, how does adding weight from there back behind center shift the bias to the front?
 
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mrblaine said:
I'm the first to admit that I'm easily confused by complex engineering answers so I need some help on that one.

If everything between the same year and equipment level TJ and TJ Unlimited is the same from the rear of the belly skid forward, how does adding weight from there back behind center shift the bias to the front?
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As I'm sure you know because of the TJ6 stuff you've done, the weight added to the rear isn't much...15" of frame, tub, roll bar and 10" of driveshaft (which only counts half for this discussion since its half unsprung)... Not much compared to the rig as a whole so the center of gravity moves back a little but not 10" or even 5", so the rear axle moves farther from the sprung COG. So if you think of the front axle as a fulcrum/pivot point and the rear as the other end of a pry bar, you're lifting a <5% larger weight with a ~10% longer lever.

I haven't run the numbers to tell the magnitude, but at worst it's exactly the same F/R as a TJ and more likely a little more F, and probably comes out pretty close to the same rear sprung weight.

I hadn't ever thought about it until I took the springs out of my TJ and put them under the LJ and lost over half an inch of FRONT ride height.
 
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freedom_in_4low said:
As I'm sure you know because of the TJ6 stuff you've done, the weight added to the rear isn't much...15" of frame, tub, roll bar and 10" of driveshaft (which only counts half for this discussion since its half unsprung)... Not much compared to the rig as a whole so the center of gravity moves back a little but not 10" or even 5", so the rear axle moves farther from the sprung COG. So if you think of the front axle as a fulcrum/pivot point and the rear as the other end of a pry bar, you're lifting a <5% larger weight with a ~10% longer lever.

I haven't run the numbers to tell the magnitude, but at worst it's exactly the same F/R as a TJ and more likely a little more F, and probably comes out pretty close to the same rear sprung weight.

I hadn't ever thought about it until I took the springs out of my TJ and put them under the LJ and lost over half an inch of FRONT ride height.
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I don't know what else you had going on but we've done many TJ Unlimited Currie spring installs as part of a full Savvy or Currie suspension install. We always use the same TJ front spring and if we try the TJ rear springs in the rear, they sag too much for them to work. We always have to use the the taller TJ Unlimited springs.
 
ok guys, maybe i panicked too early. i installed the front tires with the old springs and the extended shock picture shows about 2 inches gained there. i expect the new front springs to give slightly more front height, and the hard top and heavy spare will drop the back a little more.

jks control arms so yes rubber on the frame ends... all loose for now.

it's cold and i'm a winter wimp, so it might be spring before i get this finished. eventually i'll post a completed picture :)

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cmitcham said:
ok guys, maybe i panicked too early. i installed the front tires with the old springs and the extended shock picture shows about 2 inches gained there. i expect the new front springs to give slightly more front height, and the hard top and heavy spare will drop the back a little more.

jks control arms so yes rubber on the frame ends... all loose for now.

it's cold and i'm a winter wimp, so it might be spring before i get this finished. eventually i'll post a completed picture :)

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If you are getting 8" of lift out of those springs you need something else. 2" of downtravel isn't ok.Toss a couple tires in the back if you want to replicate a spare and fuel
 
cmitcham said:
ok guys, maybe i panicked too early. i installed the front tires with the old springs and the extended shock picture shows about 2 inches gained there. i expect the new front springs to give slightly more front height, and the hard top and heavy spare will drop the back a little more.

jks control arms so yes rubber on the frame ends... all loose for now.

it's cold and i'm a winter wimp, so it might be spring before i get this finished. eventually i'll post a completed picture :)

View attachment 482110
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Wait...was the front on jack stands when you panicked?
 
cmitcham said:
yes but lower than new ride height.

not sure i'm out of the woods yet, so i welcome any experience with these 4" LJ rockjock springs :)
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You can't make any judgement about ride height until the entire vehicle is sitting on its own weight on the tires. Put the front springs in and set it back down...then make your measurements.
 
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mrblaine said:
I don't know what else you had going on but we've done many TJ Unlimited Currie spring installs as part of a full Savvy or Currie suspension install. We always use the same TJ front spring and if we try the TJ rear springs in the rear, they sag too much for them to work. We always have to use the the taller TJ Unlimited springs.
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I don't see them listed as being for TJ or LJ, they're all just listed for both with differing lift height. 9131RH1 (TJ/LJ 3.5/3), H2 (4/3.5), and H3 (4.5/4). Which ones do you use? I have the 9132F front springs which is listed at 4" for both TJ and LJ and is what I would assume you're using in front.

Certainly differences in a build would return different results. What I know is what happened when I took a TJ off of it's springs, shocks, axles, and all 10 links and put an LJ on top of it, with the same bumpers and winch, and without any rocker guards so if the weight was all added to the rear would have worked in favor of the LJ. Yet my shock bias and uptravel went to crap and I went and bought taller springs to get it back. No change was necessary in the rear.

I don't know of anyone else that did what I did but there are examples of people getting ~1" more lift than wanted/expected when using Currie/RJ LJ springs, which is still more lift even than advertised for a TJ.
Here's an example of the H2 4/3.5 springs providing 4.5" of lift on an LJ with a hard top.
https://wranglertjforum.com/threads/currie-rear-3-inch-springs-seem-tall.71643/post-1355575

Here's one where he got 4" out of the H1 3.5/3 springs.
https://wranglertjforum.com/threads/currie-rear-3-inch-springs-seem-tall.71643/post-1356704

To go back and address the mechanics, the rear would need about 400lbs added to the rear to keep the same F/R distribution as the TJ. From what I can find the curb weight of the LJ is more than the TJ by 182lbs, so add another 218lbs in spare tire, tire carrier and bumper, corner armor and roll cage and you can probably get to where you need a taller spring, But for people like me who don't add that much weight back there, the longer spring probably isn't the right choice. For us it's more akin to an unloaded pickup truck.
 
freedom_in_4low said:
I don't see them listed as being for TJ or LJ, they're all just listed for both with differing lift height. 9131RH1 (TJ/LJ 3.5/3), H2 (4/3.5), and H3 (4.5/4). Which ones do you use? I have the 9132F front springs which is listed at 4" for both TJ and LJ and is what I would assume you're using in front.

Certainly differences in a build would return different results. What I know is what happened when I took a TJ off of it's springs, shocks, axles, and all 10 links and put an LJ on top of it, with the same bumpers and winch, and without any rocker guards so if the weight was all added to the rear would have worked in favor of the LJ. Yet my shock bias and uptravel went to crap and I went and bought taller springs to get it back. No change was necessary in the rear.

I don't know of anyone else that did what I did but there are examples of people getting ~1" more lift than wanted/expected when using Currie/RJ LJ springs, which is still more lift even than advertised for a TJ.
Here's an example of the H2 4/3.5 springs providing 4.5" of lift on an LJ with a hard top.
https://wranglertjforum.com/threads/currie-rear-3-inch-springs-seem-tall.71643/post-1355575

Here's one where he got 4" out of the H1 3.5/3 springs.
https://wranglertjforum.com/threads/currie-rear-3-inch-springs-seem-tall.71643/post-1356704

To go back and address the mechanics, the rear would need about 400lbs added to the rear to keep the same F/R distribution as the TJ. From what I can find the curb weight of the LJ is more than the TJ by 182lbs, so add another 218lbs in spare tire, tire carrier and bumper, corner armor and roll cage and you can probably get to where you need a taller spring, But for people like me who don't add that much weight back there, the longer spring probably isn't the right choice. For us it's more akin to an unloaded pickup truck.
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You're right, we don't know what we are doing.
 
mrblaine said:
You're right, we don't know what we are doing.
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dont know where you read that into what I said, but if you're not interested in having a dialog about it or acknowledging that there are multiple people having these results then I can't make you.
 
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