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JKS J spec or Rancho lift

 
Old 03-19-2019, 09:10 AM
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Default JKS J spec or Rancho lift

Just looking for opinions from people who have run either or both lifts. Iím looking at doing the JKS 3.5 inch J Spec lift or the Rancho Crawler 4 inch lift. Both are right in my price range and with Rachoís rebate right now the 4 inch lift is looking good.
This is going on a 2007 JK 2 door with auto trans with D44 and 4:11 gears. Iím looking to run 35ís comfortably off road with no rubbing. I have ready you can do the same thing on a 2.5 inch lift but for the same money why not just go up the extra 1 to 1.5 inches.
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Old 03-19-2019, 09:18 AM
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So I'll start with the standard response you're likely to see.

1. Please be sure to read this thread as it'll be helpful - https://www.jk-forum.com/forums/modified-jk-tech-2/my-thoughts-lifts-288269/

2. The difference between a 2.5 inch lift and a 3.5-4 inch lift is quite a bit. (see thread above for reference). When you get past 3" of lift, more of the suspension and steering geometry is affected. This will require more than what either of those kits are going to address.

Lifts that are in the 3.5 and above range need to address the drag link and track bar being out of parallel. Also need to address the caster being too low now (either adjustable control arms or control arm drop brackets).

What, specifically, is your goal with you rig? Light trails? High speed driving off road? Rock crawling? Mudding? That should lead you to the tire size... the tire size should lead you to the lift size.
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Old 03-19-2019, 09:33 AM
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I am bias...
But jedg brings up some good points.
We got your control arms and we address steering too.
Good luck
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Old 03-19-2019, 09:49 AM
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Originally Posted by jedg View Post
So I'll start with the standard response you're likely to see.

1. Please be sure to read this thread as it'll be helpful - https://www.jk-forum.com/forums/modified-jk-tech-2/my-thoughts-lifts-288269/

2. The difference between a 2.5 inch lift and a 3.5-4 inch lift is quite a bit. (see thread above for reference). When you get past 3" of lift, more of the suspension and steering geometry is affected. This will require more than what either of those kits are going to address.

Lifts that are in the 3.5 and above range need to address the drag link and track bar being out of parallel. Also need to address the caster being too low now (either adjustable control arms or control arm drop brackets).

What, specifically, is your goal with you rig? Light trails? High speed driving off road? Rock crawling? Mudding? That should lead you to the tire size... the tire size should lead you to the lift size.
This is going to be my sons first Jeep so I would say light off-roading just teach him.
I have owned a lot of Jeeps in my life (31 to be exact) ranging from an MB,CJís an LJ Rubicon, even an M715. This is my first JK and Iím kind of shocked that the JK needs so much more to lift it past 2.5 inches than a TJ/LJ. Iíve done a lot of reading and Iím willing run the lift and deal with the driveshaft issues later. The Rancho lift comes with adjustable arms and that was the main reason I wanted to run it, besides Rachoís reputation for quality products (they make great springs for a SOA lift on a CJ).

With the Rancho lift and a set of JKS sway bar discos what else would I need? Iíd love to just do a 3.5 Rancho lift with the arms but they seem to only offer the 4 inch Crawler.
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Old 03-19-2019, 09:55 AM
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Originally Posted by pghjeeper View Post
I have read you can do the same thing on a 2.5 inch lift but for the same money why not just go up the extra 1 to 1.5 inches.
To reinforce what jedg said, taller does NOT mean better.
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Old 03-19-2019, 09:58 AM
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So what some do (and I don't know the cost break down)
Is run our 3" SPORT, a front geo correction bracket and rear arms.
That would also be a nice setup

Rancho Control Arm Correction Brackets - RS6250B
RS66157B (rear upper)
RS66158B (rear lower)
And we still sale a TON of leaf packs too, usually RS440044



Originally Posted by pghjeeper View Post


This is going to be my sons first Jeep so I would say light off-roading just teach him.
I have owned a lot of Jeeps in my life (31 to be exact) ranging from an MB,CJís an LJ Rubicon, even an M715. This is my first JK and Iím kind of shocked that the JK needs so much more to lift it past 2.5 inches than a TJ/LJ. Iíve done a lot of reading and Iím willing run the lift and deal with the driveshaft issues later. The Rancho lift comes with adjustable arms and that was the main reason I wanted to run it, besides Rachoís reputation for quality products (they make great springs for a SOA lift on a CJ).

With the Rancho lift and a set of JKS sway bar discos what else would I need? Iíd love to just do a 3.5 Rancho lift with the arms but they seem to only offer the 4 inch Crawler.
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Old 03-19-2019, 10:05 AM
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Actually, my bad. The kit from Rancho that pulled up for me the first time didn't have the adjustable CAs. You'll still need to take a look at your steering geometry once the lift is actually on. Specifically, compare the drag link and the track bar. If these are not parallel, you'll end up with some flighty steering. Stay away from dropped pitman arms. You may need to consider a drag link flip.

The higher you go, the steeper your steering angles get. The steeper they get, the more susceptible you are to bump steer and the more shock is transmitted to your steering box. More bump force is sent down the length of the drag link and not lost thru rotation of the TRE. There are two ways to correct. A drop frame TB bracket and drop pitman arm is one way, but it lowers your roll center of the jeep, decreasing handling in corners. So it is advised against. Flipping the DL and raising the axle TB mount is the better method. It raises the roll center increasing handling. The key to either setup is the track bar and the draglink have to remain both parallel to each other, and in the same plane. You can not run a DL flip with drop frame TB mount, and you cannot run a drop pitman arm with raised axle TB mount. The ideal setup is both links perfectly parallel to the ground, raised, in the same plane. This is close to how it comes from the factory (slight angle) and to achieve this at higher lifts you may have to increase bump stops or notch frame.
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Old 03-19-2019, 10:53 AM
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Originally Posted by jedg View Post
Actually, my bad. The kit from Rancho that pulled up for me the first time didn't have the adjustable CAs. You'll still need to take a look at your steering geometry once the lift is actually on. Specifically, compare the drag link and the track bar. If these are not parallel, you'll end up with some flighty steering. Stay away from dropped pitman arms. You may need to consider a drag link flip.

The higher you go, the steeper your steering angles get. The steeper they get, the more susceptible you are to bump steer and the more shock is transmitted to your steering box. More bump force is sent down the length of the drag link and not lost thru rotation of the TRE. There are two ways to correct. A drop frame TB bracket and drop pitman arm is one way, but it lowers your roll center of the jeep, decreasing handling in corners. So it is advised against. Flipping the DL and raising the axle TB mount is the better method. It raises the roll center increasing handling. The key to either setup is the track bar and the draglink have to remain both parallel to each other, and in the same plane. You can not run a DL flip with drop frame TB mount, and you cannot run a drop pitman arm with raised axle TB mount. The ideal setup is both links perfectly parallel to the ground, raised, in the same plane. This is close to how it comes from the factory (slight angle) and to achieve this at higher lifts you may have to increase bump stops or notch frame.
Well sounds like the JKS kit is out if I go 3.5 due to the lack of adjustable arms or correction brackets.

So so could I get the Rancho 4 inch Crawler put it on and then add on as I go?
Is the bump steer any worse in a lifted JK vs a Lifted TJ?
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Old 03-19-2019, 10:53 AM
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Originally Posted by Rancho View Post
So what some do (and I don't know the cost break down)
Is run our 3" SPORT, a front geo correction bracket and rear arms.
That would also be a nice setup

Rancho Control Arm Correction Brackets - RS6250B
RS66157B (rear upper)
RS66158B (rear lower)
And we still sale a TON of leaf packs too, usually RS440044

At that point Iíd just do the 2.5 inch lift
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Old 03-19-2019, 11:32 AM
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Originally Posted by pghjeeper View Post
Well sounds like the JKS kit is out if I go 3.5 due to the lack of adjustable arms or correction brackets.
So so could I get the Rancho 4 inch Crawler put it on and then add on as I go?



Think about those two sentences. Lift 1 is out because it doesn't come with a component, but then you ask if you can add components to lift 2? You can add components to ANY lift. At ANY time.

This is my first JK and I’m kind of shocked that the JK needs so much more to lift it past 2.5 inches than a TJ/LJ.
Take what you are reading as suggestions, not mandatory fact. If you want to slap 4" spacers on top of the coils and absolutely no other components, go for it. It'll drive. Just don't expect to be happy with the results. What you are reading are experiences from people who have built these JK's and experienced many of the negatives associated with lifting. Listen to the advice, research the issues, then form your own opinions about what is right for you.

At that point I’d just do the 2.5 inch lift
Are you staying with stock flares? Or are you willing to move to flats or trim the stock fenders? 2.5" with trimmed/flats is plenty for 35's. One other thing to keep in mind when researching the various lifts is that you can expect different 'actual measured' lift heights from various coils, regardless of what is printed on the side of the box. 3-3.5" from 2.5" coils is not unheard of. I am sitting in the 4.5-5" range on my 3.5" MetalCloak coils. Even with stock uncut fenders, there is a bunch of space for my 37" tires.

Last edited by nthinuf; 03-19-2019 at 11:36 AM.
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