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Longarms (not what you're thinking)

D

Drunk tank

NAXJA Forum User
Location
San Clemente, CA
Well with everyone going to long arms of one form or another....

One thing I havnt seen discussed is the pro's and cons of each system. essentually there looks to be two style to go with; Radius arms and long 4 links.

My question is what are the pros and cons of each system.... or what makes one system better than the other?

The main benifit I can see in the longer 4 link is that as the axle travels....the caster would remain relativly the same throughout the range of motion. Where as with the radius srms it would change.

That just one of my observations... sure someone here knows alot more about suspension setups than i do and can clear this up for me.
 
You are right. There are two basic types of long-arms, radius arm and 3 or 4 link.

IMHO what it boils down to is simplicity in manufacturing and packaging. A radius arm set-up like RE, TNT, Rustys, Clayton's, Fabtech, ect...only has one pivot point somewhere near the crossmember and two connections at the axle. This is a very strong and simple setup that is very effective if wheel travel is limited as the caster wont change too dramatically. The problem arises when you try to force articulation as the axle tube will want twist like a torsion bar. This puts tremendous stress on all four of the mounting points, prematurely wearing all the bushings.

There are two others though that are trying to make a better product, albiet using different schools of thought.
Full-Traction has a true 4-link, long-arm that will ride alot like a stock Jeep, as its still the same design, just longer ( and alot beefier) than stock. This design will still bind (twist) the axle tubes, but not to such an extent.
Rock Krawler on the other hand uses a 3-link design that uses two lowers and one upper arm. There is NO BIND in this configuration. Take a look at many competion crawlers and they running similar designs. Even a few enterprising groups have taken this design and improved it like URF (Goatman, Crash, Kd4lyf...) for better ground clearance.
The 3,4-link systems are more complex and more expensive but they have far better handling more predicable behaviour off-road. Find someone with each style and ask for a ride to see for youself.
 
Unless you're doing desert prerunning, you're not going to have enough on-road suspension travel for the caster change with radius arms to be an issue, unless you run a rediculously soft suspension.
 
jpnjason said:
You are right. There are two basic types of long-arms, radius arm and 3 or 4 link.

IMHO what it boils down to is simplicity in manufacturing and packaging. A radius arm set-up like RE, TNT, Rustys, Clayton's, Fabtech, ect...only has one pivot point somewhere near the crossmember and two connections at the axle. This is a very strong and simple setup that is very effective if wheel travel is limited as the caster wont change too dramatically. The problem arises when you try to force articulation as the axle tube will want twist like a torsion bar. This puts tremendous stress on all four of the mounting points, prematurely wearing all the bushings.

There are two others though that are trying to make a better product, albiet using different schools of thought.
Full-Traction has a true 4-link, long-arm that will ride alot like a stock Jeep, as its still the same design, just longer ( and alot beefier) than stock. This design will still bind (twist) the axle tubes, but not to such an extent.
Rock Krawler on the other hand uses a 3-link design that uses two lowers and one upper arm. There is NO BIND in this configuration. Take a look at many competion crawlers and they running similar designs. Even a few enterprising groups have taken this design and improved it like URF (Goatman, Crash, Kd4lyf...) for better ground clearance.
The 3,4-link systems are more complex and more expensive but they have far better handling more predicable behaviour off-road. Find someone with each style and ask for a ride to see for youself.
Click to expand...

Ah... forgot about the triangulated 3link. One main issue Ive seen with that is the triangulated upper link carrying the lateral loads (essentually acting as a panhard)

When it becomes time to go to long arms... thatll be my route. haha... anyone know about trussing a D30 and making a center mount for a three link?
 
Drunk tank said:
Ah... forgot about the triangulated 3link. One main issue Ive seen with that is the triangulated upper link carrying the lateral loads (essentually acting as a panhard)

When it becomes time to go to long arms... thatll be my route. haha... anyone know about trussing a D30 and making a center mount for a three link?
Click to expand...


Also budget for full hydro steer if you are doing a triangulated 3 link. You can't expect a standard linkage steering to follow the perfectly vertical axle travel dictated by the triangulated linkage.

A steering linkage that parralels the upper arm would work, however.

CRASH
 
The reason The triangulated 3-link was not mentioned was because only company make one...Teraflex.

I don't know about you but I've NEVER seen one being driven. Not to mention the fact that I've never heard a good thing said about it, the problem, steering. Like Crash said, you can not make a typical steering work, there for this is an undesirable setup.






If you want travel, durability, and good ride......go with 3 individual links.
 
Tera's LCG system (for TJ's) uses a triangulated 4-link front and rear. They intend for their high-steer D30 knuckle (or some other high-steer setup) to be used with it, so that the draglink is perfectly flat at static height to reduce bumpsteer on the road.
 
Jeepin Jason said:
Tera's LCG system (for TJ's) uses a triangulated 4-link front and rear. They intend for their high-steer D30 knuckle (or some other high-steer setup) to be used with it, so that the draglink is perfectly flat at static height to reduce bumpsteer on the road.
Click to expand...

That doesn't really help at 70 mph through the desert, though, does it?

CRASH
 
CRASH said:
That doesn't really help at 70 mph through the desert, though, does it?

CRASH
Click to expand...

I rarely go 70mph on PAVEMENT. You think I care aboot desert prerunning? :gag: :D

Tera didn't design that kit for prerunning, they designed it for crawling. It's a TJ kit anyway. I think you'd be pretty nuts to go 70mph through the desert in a SWB TJ.
 
i didn't see it mentioned, maybe i missed it, but one of the main advantages of a non-triangulated 3 or 4 link is control over anti-dive. though a radius arm is easy to design and fabricate, it will typically have tons of anti-dive and have a strong tendency to unload on climbs, though this can be rememdied to a degree by limiting straps.

if you have time and inginuity build a non-triangulated 3 or 4 link, if you want something that is simple and proven though not the absolute best, do radius arms, or leafs for that matter :laugh3:
 
Unloading was the thing I hated about my old radius arm set up. Tons of anti-dive.

CRASH

BrettM said:
i didn't see it mentioned, maybe i missed it, but one of the main advantages of a non-triangulated 3 or 4 link is control over anti-dive. though a radius arm is easy to design and fabricate, it will typically have tons of anti-dive and have a strong tendency to unload on climbs, though this can be rememdied to a degree by limiting straps.

if you have time and inginuity build a non-triangulated 3 or 4 link, if you want something that is simple and proven though not the absolute best, do radius arms, or leafs for that matter :laugh3:
Click to expand...
 
jpnjason said:
The reason The triangulated 3-link was not mentioned was because only company make one...Teraflex.

I don't know about you but I've NEVER seen one being driven. Not to mention the fact that I've never heard a good thing said about it, the problem, steering. Like Crash said, you can not make a typical steering work, there for this is an undesirable setup.

If you want travel, durability, and good ride......go with 3 individual links.
Click to expand...

Hmmmm, mine hit 80MPH on the way home from work this morning. Just because it isn't on a shelf in a shop doesn't make it impossible. I have all the travel I need, it's been pounded on for over a year, and it rides better than stock. Don't be afraid to think outside the XJ box.

-Jon
 
so after reading jpnjason's post and others on this board, it seems that Full-Traction and Rock Krawler make the best kits... what are the drawbacks for those kits?

I understand the drawbacks for a fully triangulated 3link and for normal radius bars that most "long arm" kits really are.

I'm looking for that perfect setup for a jeep that sees 30% daily driver, 30% rock/trail, and 30% desert medium speed.
 
Drunk tank said:
Well with everyone going to long arms of one form or another....
Click to expand...

Who said everyone's going to long arms?

Many are going to long arms, but not even most. It is a good idea, however, to discuss the pros and cons of the various types.

I'm not a fan of radius arm style long arms, though they can be pretty simple to make. When the mounts are tucked up tight inside the frame rails to achieve acceptable ground clearance, then the arm angle is increased which slightly decreases the benefit of the longer arms. Also, the RE style (lack of a better term) long arms are very hard on upper axle mounts, so care needs to be taken when making mounts and choosing bushings or joints.

As most people know, overall I'm not a fan of long arms unless good ground clearance can be maintained. In many cases the benefits don't end up outweighing the downsides. However, some of the folks around here have come up with very good long arm designs, though it's not easy to do. The URF style 3 link long arm is excellent, and has none of the potentially negative qualities that are inherent in many long arm set ups. The mounts are tucked up inside the frame rails, the arms angles are very good, and the 3 link eliminates any potential binding. Eliminating the binding allows the use of harder joints which then minimizes any tendancy for front axle wrap.
 
Last edited:
Ok, but most agree that with short arms, if you have over 4.5" lift, then you probably want drop brackets... but back to the long arm type discussion?
 
kristoffers said:
Ok, but most agree that with short arms, if you have over 4.5" lift, then you probably want drop brackets... but back to the long arm type discussion?
Click to expand...
One of the things I've seen bantered about with the lifted short arm kits on TJs is that when applying power with the wheels turned it is easy to lift a front tire - maybe even a rear tire because of the jacking that occurs with arm angles relative to the ground. These are kits that don't use DBs.

Has anyone seen this occur on a lifted XJ? I'd expect so since the front is more or less identical to a TJ. Any one have first hand experience with this? If you did, did adding DBs mitigate this?

A true 3 or 4 link could potentially reduce this, right?

Just curious.

r@m
 
Root Moose said:
One of the things I've seen bantered about with the lifted short arm kits on TJs is that when applying power with the wheels turned it is easy to lift a front tire - maybe even a rear tire because of the jacking that occurs with arm angles relative to the ground. These are kits that don't use DBs.

Has anyone seen this occur on a lifted XJ? I'd expect so since the front is more or less identical to a TJ. Any one have first hand experience with this? If you did, did adding DBs mitigate this?

A true 3 or 4 link could potentially reduce this, right?

Just curious.

r@m
Click to expand...

I've never seen or heard of anyone experincing this in an XJ...someone needs to speak up if they have. There is a big difference between the handling of a front coil/rear leaf suspension and the front/rear coil suspension of a TJ.

Just for the record, an XJ or TJ front suspension is a true 4 link, don't know what you mean by the "true 3 or 4 link" comment.

Regarding drop brackets, to me they are easily as good an option to gain better control arm angles than all or nearly all bolt on long arm kits. At least the loss of ground clearance is closer to the tire so the breakover angle isn't compromised as much as it is with bolt on long arm kits. Sort of a toss up between the two, IMHO........but drop brackets aren't as cool. :)
 
Root Moose said:
One of the things I've seen bantered about with the lifted short arm kits on TJs is that when applying power with the wheels turned it is easy to lift a front tire - maybe even a rear tire because of the jacking that occurs with arm angles relative to the ground. These are kits that don't use DBs.

Has anyone seen this occur on a lifted XJ? I'd expect so since the front is more or less identical to a TJ. Any one have first hand experience with this? If you did, did adding DBs mitigate this?
Click to expand...

I have, personally, real life, regular basis, lifted the driver's front tire off the ground on flat city streets. I never did get around to taking a picture of this activity, but an XJ WILL lift tires on the street, running short arms, stock location, big lift.

I have not yet added DBs to this Jeep, but I'm planning on it. FWIW, I haven't tried lifting the tire since I swapped out the spool for a Detroit.
 
kristoffers said:
I'm looking for that perfect setup for a jeep that sees 30% daily driver, 30% rock/trail, and 30% desert medium speed.
Click to expand...

That depends on how much fab work you're willing and able to do, or if you need to buy bolt on. It also depends on which elements are the most important to you. If you're talking fabbing, I can talk about a couple of ways to get you what you want. If it's bolt on, I don't have any personal experience with any of them. I do know that I like the Full Traction stuff, it's well thought out and designed with plenty of strength, and should handle very well. It's drawback is the same as every other bolt on long arm kit, the lower control arm frame mounts are located underneath the frame rail significantly reducing ground clearance. So, for the street and for desert speed it will work very well, for rocks it should perform well other than the increased risk of getting hung up on the mounts....and in rocks, getting hung up stops you more often than a lack of traction.
 
I agree that short arm with drop brackets may be better than some long arm kits is certain ways... however I do think the new kit from TNT is the best radius arm type long arm setup out there right now.

I still want to hear more about pros/cons of a 3 link setup like that from RockKrawler? I know, I should do some searching on the rest of the net... but the pros on NAXJA always seem to be able to distill it down so well for us common folk!
 
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