Short Arm/Long Arm
JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
I have seen JK's on 4" of lift and 37's performing perfectly on and off the trail. Have any doubts, just check out all that Off Road Evolution has done with their JK Sahara Unlimited.
The whole point behind the long arm kit design on previous Jeeps was to correct suspension geometry after going 4" or taller and make them more comfortable, stable and provide a ride closer to stock. Need I say, I'm not 100% sure what the point of a long arm kit on a JK is yet. In my opinion, I wouldn't be so eager to hack up, drill and or weld things onto your new Jeep unless it is proven to really benefit it. But then, that's just me.
The whole point behind the long arm kit design on previous Jeeps was to correct suspension geometry after going 4" or taller and make them more comfortable, stable and provide a ride closer to stock. Need I say, I'm not 100% sure what the point of a long arm kit on a JK is yet. In my opinion, I wouldn't be so eager to hack up, drill and or weld things onto your new Jeep unless it is proven to really benefit it. But then, that's just me.
JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
If you are going to go 4" and run 37's, you should probably seriously consider a long arm kit like the new one just released by Rubicon Express.
To quickly understand the difference of a short arm vs a long arm, grab a full-length pencil and hold it horizontally between your two hands. While holding one end stationary (simulates frame side of suspension arm), move the other end up and down vertically 1" (axle side of arm). Notice a couple of things. First, the angle of the pencil varies by 10-15 degrees. Second, and perhaps more importantly, when you articulated the end point of the pencil, your two hands didn't become that much closer together.
To exaggerate the differences of short arm vs long arm, repeat the above using a toothpick. Notice the two difference from the pencil. First, the angle of the toothpick has to be much greater to accomodate the up/down motion at one end. Secondly, the horizontal measurement becomes significantly shorter when the toothpick is at its maximum angle. On your Jeep, for the same amount of flex, a long arm will have less tendency to "pull" the axle back on the flex side because of the angle of the locating arms.
Clear as mud? Sorry if the analogy doesn't work for you - it's one of my favorites!
To quickly understand the difference of a short arm vs a long arm, grab a full-length pencil and hold it horizontally between your two hands. While holding one end stationary (simulates frame side of suspension arm), move the other end up and down vertically 1" (axle side of arm). Notice a couple of things. First, the angle of the pencil varies by 10-15 degrees. Second, and perhaps more importantly, when you articulated the end point of the pencil, your two hands didn't become that much closer together.
To exaggerate the differences of short arm vs long arm, repeat the above using a toothpick. Notice the two difference from the pencil. First, the angle of the toothpick has to be much greater to accomodate the up/down motion at one end. Secondly, the horizontal measurement becomes significantly shorter when the toothpick is at its maximum angle. On your Jeep, for the same amount of flex, a long arm will have less tendency to "pull" the axle back on the flex side because of the angle of the locating arms.
Clear as mud? Sorry if the analogy doesn't work for you - it's one of my favorites!
Thread Starter
JK Enthusiast
Joined: Feb 2007
Posts: 146
Likes: 0
Although you are complete correct in your analogy, it should be noted that the control arms on a JK are longer than on a TJ. Also, I would argue that you should really try riding in a 4" lifted JK on short arms (I have) before you make the assumption that it's suspension geometry needs to be fixed. Yes, on paper it makes sense and technically, you might even get a slightly better ride but I'd have to wonder if the significantly higher price of a long arm kit is really worth it at just 4" of lift.
Yeah that is what i am wondering. All those jk's with 4" Superlift arent complaining yet. But is that because they havent been driven enouph to notice the bad ride quality yet?
Thread Starter
JK Enthusiast
Joined: Feb 2007
Posts: 146
Likes: 0
If you are going to go 4" and run 37's, you should probably seriously consider a long arm kit like the new one just released by Rubicon Express.
To quickly understand the difference of a short arm vs a long arm, grab a full-length pencil and hold it horizontally between your two hands. While holding one end stationary (simulates frame side of suspension arm), move the other end up and down vertically 1" (axle side of arm). Notice a couple of things. First, the angle of the pencil varies by 10-15 degrees. Second, and perhaps more importantly, when you articulated the end point of the pencil, your two hands didn't become that much closer together.
To exaggerate the differences of short arm vs long arm, repeat the above using a toothpick. Notice the two difference from the pencil. First, the angle of the toothpick has to be much greater to accomodate the up/down motion at one end. Secondly, the horizontal measurement becomes significantly shorter when the toothpick is at its maximum angle. On your Jeep, for the same amount of flex, a long arm will have less tendency to "pull" the axle back on the flex side because of the angle of the locating arms.
Clear as mud? Sorry if the analogy doesn't work for you - it's one of my favorites!
To quickly understand the difference of a short arm vs a long arm, grab a full-length pencil and hold it horizontally between your two hands. While holding one end stationary (simulates frame side of suspension arm), move the other end up and down vertically 1" (axle side of arm). Notice a couple of things. First, the angle of the pencil varies by 10-15 degrees. Second, and perhaps more importantly, when you articulated the end point of the pencil, your two hands didn't become that much closer together.
To exaggerate the differences of short arm vs long arm, repeat the above using a toothpick. Notice the two difference from the pencil. First, the angle of the toothpick has to be much greater to accomodate the up/down motion at one end. Secondly, the horizontal measurement becomes significantly shorter when the toothpick is at its maximum angle. On your Jeep, for the same amount of flex, a long arm will have less tendency to "pull" the axle back on the flex side because of the angle of the locating arms.
Clear as mud? Sorry if the analogy doesn't work for you - it's one of my favorites!
Great explanation.
Could not be any clearer. What size lift on a jk since the arms are longer would you need to change over to a long arm lift? 4"?5"? 6"?
JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
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JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
I think it'd be hard to say for sure until people start running that tall but I'd be willing to bet you'd need to start thinking long arms at about 6".
JK Freak
Joined: Nov 2006
Posts: 522
Likes: 0
From: Lander, Wyoming
I have seen JK's on 4" of lift and 37's performing perfectly on and off the trail. Have any doubts, just check out all that Off Road Evolution has done with their JK Sahara Unlimited.
The whole point behind the long arm kit design on previous Jeeps was to correct suspension geometry after going 4" or taller and make them more comfortable, stable and provide a ride closer to stock. Need I say, I'm not 100% sure what the point of a long arm kit on a JK is yet. In my opinion, I wouldn't be so eager to hack up, drill and or weld things onto your new Jeep unless it is proven to really benefit it. But then, that's just me.
The whole point behind the long arm kit design on previous Jeeps was to correct suspension geometry after going 4" or taller and make them more comfortable, stable and provide a ride closer to stock. Need I say, I'm not 100% sure what the point of a long arm kit on a JK is yet. In my opinion, I wouldn't be so eager to hack up, drill and or weld things onto your new Jeep unless it is proven to really benefit it. But then, that's just me.
Papabear