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Forums | SWB Technical Forum | Rock Krawler Long Arm 3 Link Thread Closed Send Topic To a Friend
Topic is 3 Pages Long:    1 2 3 
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T&ERun
Ellisville, MO
Online Member
Posted - 16 April 2014 7:3  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Who's running it and how do you like it? Any issues at all? I'm mainly talking about the three link setup as there's many options as far as coils, coil overs, etc. Do you like the 3 link on the street? Thanks
Stalker

In a Jeep
Down by the River, IL
MWJT President
Posted - 16 April 2014 23:30  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
I have their TJ X Factor Plus Long Arm Upgrade kit with the 3 link front and haven't had any problems. I think the ride is good on the road, but I'll know more after I replace the tires and wheels (mine aren't exactly in ideal shape) My springs, shocks and other components are a mix of parts, so it's not their complete kit.

But to answer your question, no problems with the 3 link on the street.

pudggie
Oakville, MO
Club Member
Posted - 19 April 2014 22:35  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Ive got the rock krawler lcg x factor on a lj if youd like to check it out in person before you drop that kind a coin on it.

I love the way it rides

Email me at pudggie at gmail.com

chrispy
, CO
Online Member
Posted - 23 April 2014 10:42  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
only issue with a 3 link on the street/highway is an utter lack of redundancy. if you check all your brackets meticulously, and often for cracks, damage, torque, etc, shouldn't have any problems... but if anything breaks at highway speeds, its not good. with a 4 link, if you have a link break, it will get squirrel and youll hear the 'pop', but, chances are youll be able to get it off the road without serious injury.

im sure they 'drive nice', but, id have a hard time putting highway miles on a 3 link for safety reasons alone.

Mr Moke
St Peters, MO
MWJT Director of Events
Posted - 23 April 2014 11:55  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
I have always held to the same theory as Chrispy just stated.
That being said, however, we only have one track bar, one tie rod, one steering shaft......
T&ERun
Ellisville, MO
Online Member
Posted - 23 April 2014 23:4  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Thanks for the input. I decided on the EVO longarm upgrade. Staying 4 link.
Stalker

In a Jeep
Down by the River, IL
MWJT President
Posted - 24 April 2014 22:30  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
The rock krawler does have a 4 link kit. It's the same as the 3 link, but without the 4th link. So you could have the 4 link on the highway and pull the 4th link to go offroad. Kind of a pita for a short trip, but on a week long trip to Moab maybe. Odds are you'd never put the 4th back in though.
Mr Moke
St Peters, MO
MWJT Director of Events
Posted - 25 April 2014 7:25  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
What is the reasoning behind a 3 link rather than 4?
hack
Glencoe, MO
MWJT Vice President
Posted - 27 April 2014 6:46  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Flex. Less stuff to bind
Stalker

In a Jeep
Down by the River, IL
MWJT President
Posted - 27 April 2014 21:48  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
With a 4 link where the uppers branch off the lowers it's easy to see.

When both sides flex together either upward or downward, everything is fine. No biggie. (Frames 1, 2, and 3)

But when one side goes up and the other goes down it tries to twist the axle from one end of it to the other. (Driver's side to passenger side)

Watch the last frame of this .gif and you can see the triangles each arm makes between the upper and lower axle end links are pointing in different directions.
This means that it's trying to twist the axle which is putting things in a bind.

With a 3 link, you only have the three links, so you're not trying to twist your axle apart.

Now that said, a 'triangulated' 4 link is much better because it puts the two upper links very near each other on the axle end in the center of the axle to minimizing the binding.

In other words, it acts more like a 3-link

hack
Glencoe, MO
MWJT Vice President
Posted - 1 May 2014 16:51  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Aaron, your .giftastic!
chrispy
, CO
Online Member
Posted - 1 May 2014 18:46  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
unfortunately, a link system that puts the uppers off the lowers is not a 4 link.. its a 2 link.(or radius arm suspension) with only 2 frame connections. it offers zero control of the axle side to side, and again, you have to be 100% sure of your frame side connection. another problem with this type of suspension is basic physics.. when you approach an obstacle, the axle will want to push down under it, rather than climb. with a true 4 link, you will have upper and lower frame mounts, and this will typically climb better.

sure, if you want to be a ramp champ, these type of systems do have 'more flex', but do you really need it? is it helping you or beneficial in any way? in most cases, its actually hurting you, and many manufacturers build this type because it is cheaper to produce... not because its better.

additionally, Radius arms really have to be flat to work well. If not they have too much anti squat (or anti dive) when lifted. most jeeps cannot get flat lower arms, you really have to move a lot of metal to make this work right.. but on a buggy with flat arms, it can be made to work well.

look at aarons gif above.. first, his frame mount is a foot or more below the frame.. can you imagine having a mount that low? if you correctly draw the picture above, youll see the angle to be extremely steep. this leads to death wobble, wheelbase changes when it droops, etc etc... generally bad things.

also, with only 2 frame mounts imagine how much stress is on those mounts. doesn't matter if your using heims, bushings, johnny joints or whatever, they are going to wear quite a bit faster than with 4 frame mounts.

a decent 4 link (5 link) works very well with coil overs.. as will a triangulated 4 link, if done properly.

anyway.. lots more on it. i think many people like the 'three link' because they see the buggy guys run it.. folks that typically do three links because it saves room under the rig, saves weight, etc, and they don't have to drive the rigs home..just to the trailer.


Edited by - chrispy on 5/1/2014 6:51:12 PM

xj_zach
waterloo, IL
Online Member
Posted - 2 May 2014 20:40  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
^ Yes to like, everything Chrispy just said. Most importantly noting that radius style set ups are definitely not the same as individual upper/lower link suspensions.
Stalker

In a Jeep
Down by the River, IL
MWJT President
Posted - 2 May 2014 21:25  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
Yeah, I guess the radius arm I illustrated above is usually referred to as "long arm" more often than 4 link.

And I greatly exaggerated the frame height and other proportions so you could more easily see the binding. There's no scale that was used. It was just a quickly mocked together thing.

My bad.

chrispy
, CO
Online Member
Posted - 2 May 2014 21:45  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
"long arm" typically refers to moving the frame mounts farther away from the axle. this can be just about any type of linked suspension and is not associated with any particular style


"radius arm" suspension typically has the upper link attached to the lower link. Ford is most well known for their radius arm suspensions, however, they use a completely different type of joint at the frame.

anyway, i do not recommend radius arm setups on street driven jeeps. several aftermarket companies use radius arm setups, rubicon express for one, TNT for another.. but they do handle quite a bit differently than a 3 or 4 link setup with upper and lower frame mounts... typically quite a bit worse on road as anti squat is difficult to get right, and there very little control of the axle. they do have less binding, which can make them popular on trailerd rigs, or buggies... but on a stock bodied rig, its not to difficult to come up with a very good working 4 link.. and no real reason to run a 3 link or radius arm.

Mr Moke
St Peters, MO
MWJT Director of Events
Posted - 2 May 2014 22:58  Show Profile  Email Poster  Edit or Delete Message  GoTo Member Rides
When my TJ with 'RE long arms (radius arms in front) isn't in need of some maintenance, I'll rank it up there as one of the best road driving Jeeps I have ever driven. Smooth, not at all choppy, never any death wobble, and tracks durn near laser straight.
Right now she needs some tightening up but still no wobble.
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