long arm vs. short arm

[hadAjeep]

I've been reading about long arm kit's and short arm kits but haven't really found why one is needed over the other. Or what the advantage is. Anyone out there care to explain the difference.

 

[xj92]

Longer arms have a wider arc, making the up-down movement of the axle more straight up and down than with a smaller arc. Because the arc is wider, you'll get more downward movement with long-arms on a stock D30 axle because of the LCA bracket design. You can compensate for this with short arms by modifying the bracket (chop chop) or putting a bend in the LCA's to compensate for it.

The angle of long-arms will be flatter vs. short arms with the same amount of lift, unless you're using drop brackets on short arms, and this is what provides the better ride. Long arms hang down lower and further back typically, so you lose a slight amount of clearance. Long arms have a tendency to unload on steep climbs, which you can counteract with a center limiting strap.

That'll start the discussion, then we can talk about long 4-link vs. long radius arms .

 

[Ramsey]

can someone explain to me why they unload, and if they always do it

 

[PapaPump]

long arms are radius arms that force the axle to follow an arc (except for full traction's). with short arms you can get the axle to follow a straight up and down line. long arms should increase travel, especially compared with an uncut lca bracket, like was said before, becase the relative angles are decreased. radius arms will probably increase bump steer because they do get rid of the inherent advantage of the 4 link setup. it does seem weird to me to change to long arms for travel only to limit it with straps. IMO drop brackets with 4 link retained is the way to go, unless you have money to spare. with enough money you can have longer arms, longer shocks, good geometry and all that stuff. on my budget you cut the fenders and get some body damage.

 

[xj92]

with short arms you can get the axle to follow a straight up and down line.

The pinion may move straight up and down (at least if the arms were of the same length), but the axle still moves back as both arms cycle downward.

it does seem weird to me to change to long arms for travel only to limit it with straps.

The limiting strap goes in the middle of the axle to prevent unloading past a certain point, the ends are still open for increased articulation.

 

[CW]

Dear God not again! Watch out for Goatman.
Seriously search. They just end up as ****ing matches though..
Heres a good one. It should cover anything you can think of, as far design.
http://www.naxja.org/forum/showthread.php?t=15764&highlight=long+arm+short
This will make your head hurt but you should be able to it figure out eventualy (maybe)
http://www.pirate4x4.com/forum/showthread.php?t=168577&highlight=suspension

 

[Starboard M]

"When trolling for Goatman, mention long arms"
From what Ive learned, long arms are suposed to handle a lot better on the street. The also are suposed to have greater flex, but I havnt seen that proven. To me, short arms work really well, and I never plan on changing. Having the la hang down so much and cost just turn me away from them, so Im sticking with my shortys

 

[hadAjeep]

So are most suspension kits short arm then? I've seen some advertised as long arm. So long arm kits probably involve some cutting and welding while short arm kits just bolt on? All I really need to know is, can I stuff 33's or 35's with a lift kit that isn't a long arm kit. Thanks.

 

[OT]

So are most suspension kits short arm then? I've seen some advertised as long arm. So long arm kits probably involve some cutting and welding while short arm kits just bolt on? All I really need to know is, can I stuff 33's or 35's with a lift kit that isn't a long arm kit. Thanks.

Whether you have a LA or SA system, you can mount whatever size tire your crazy ol' mind can fit. The tire size issue is one you'll have to take up with you fenders.

 

[old_man]

I'm talking from experience, not just theory. I have built and run both. The "long" arm setup rides much smoother on the street and the trail. It's a matter of geometry, cosine exactly. What makes a short arm ride harsh has to do with the downward angle. If the tire is forced upwards, because of the angle of the arm, the body is forced backwards and when the tire goes down the body is forced forward. That is why you get the "harsh" ride. A longer arm lessens the angle the arm has to traverse to get the same tire movement, thus the less the forward and backward accelleration of the body on a bump, yielding smoother ride.

A properly set up long arm setup has more travel capability in theory, but most flex is limited by the shocks on most vehicles anyway. That is why you see people running shock hoops, it allows a longer shock and a longer shock equals longer travel.

I like long arms and I am running a set I built on my XJ. I am currently building a full width high pinion Dana 44 for the front and I will be using radius arms. They are a lot like long arms but have other interesting properties. The main reason I am doing the radius arms is that they came with the axle and are cheap.

 

[Immortal]

I built my own long arms which in turn moved my front axle forward 3" to better center my wheels in the wheel wells with 9" of lift with 35's......much much much smoother ride and handling on and off road.......quick question my set up is a 3link with the 3rd link goin from the top of the pinion to a point on the lca of the drivers side.........is it really necessary to do this to the passenger side?

 

[wannabe]

I built my own long arms which in turn moved my front axle forward 3" to better center my wheels in the wheel wells with 9" of lift with 35's......much much much smoother ride and handling on and off road.......quick question my set up is a 3link with the 3rd link goin from the top of the pinion to a point on the lca of the drivers side.........is it really necessary to do this to the passenger side?

Nope

 

[Goatman]

"When trolling for Goatman, mention long arms"

Yep.........sounds like a Goatman troll to me



The issue is control arm angles, and improving the arc that the axle travels in when the suspension cycles. There are a number of ways to improve control arm angles, with "long arms" being one of them. Changing the mounting position of the arms also helps, like using drop brackets or fabbing up something with a little more clearance. Making the arms a little longer and also moving the mounting locations is the best solution in my opinion, which is a mid arm, but no one makes a kit for it. The Currie J arms are the closest thing, and they work.

If you have to buy something, your choice is drop brackets or low hanging long arms, and both decrease ground clearance. If you're going to fab something up, I just can't see fabbing up a long arm on an XJ unless you do something like CRASH just did, but that takes a lot of skill and a commitment to not get a ration of crap from me.

 

[hadAjeep]

Ok, I don't even have an XJ yet but the kit I'm looking at is the RE 6130 so I can run 33's. It doesn't say long arm so I'm guessing it's not. My friends MJ has a 2-3 inch skyjacker lift with new springs in the front and new control arms. It rides rougher on the trails than my 3/4 ton Ram. Granted he uses the skyjacker cheapo shocks and I've got a T-REX suspension. So the harsh ride is the short arms huh? Would better shocks help? Man did I open a can o worms here. Thanks for the info so far.

 

[Loose_Nuts_Enterprises]

On my set up, I raised the LCA attachments so that the bottom of the arms are even with the bottom of the axle tube. Then I lowered the frame attachment of the UCAs to get the better geometry back to emilinate the crazy brake dive I had before re-doing the uppers. The angles of the CAs are real close to what a long arm kit would afford, without the loss of ground clearance. The ride is much better on and off road, and I'm not getting hung up on the arms any more either. I still have plenty of articulation. Once the coils are unseated, the only traction you're getting is from unsprung weight on that dropped out tire, which isn't much anyway.


Dan

 

[Goatman]

Ok, I don't even have an XJ yet but the kit I'm looking at is the RE 6130 so I can run 33's. It doesn't say long arm so I'm guessing it's not. My friends MJ has a 2-3 inch skyjacker lift with new springs in the front and new control arms. It rides rougher on the trails than my 3/4 ton Ram. Granted he uses the skyjacker cheapo shocks and I've got a T-REX suspension. So the harsh ride is the short arms huh? Would better shocks help? Man did I open a can o worms here. Thanks for the info so far.

A harsh ride can come from any number of things. Some people even look at the tire pressure on the side of a tire (which is used for that tire's weight rating) and fill them to that pressure.......which is usually way to much and will give a harsh ride. Some shocks are just too stiff, or are poor quality, and give a harsh ride all by themselves. Also, many rear spring packs are just too stiff, with too stiff a spring rate or add-a-leafs or too much friction between the individual leaves.

On a tall lift, starting probably between 3-4", the control arm angles are getting steep enough to effect the ride, and it gets worse as the lift increases. Because the control arms are pointed down so much the axle/tire must move forward as well as upwards when hitting a bump, and this increases the harshness. Flatening out the arm angles, regardless of how it's accomplished, will improve the ride.

Someone asked about unloading. Unloading is when the front of the rig floats up on steep climbs due to weight transfer, leaving the front with much less traction and putting the rig in an unstable position. One reason long arms tend to increase unloading is that the weight of the front axle/tires/wheels is working (think pulling down) on the rig at a point further back on the frame. Obviously, the further forward weight is distributed the more it will pull down on the front of the vehicle, and more weight forward is better on steep climbs. Since the weight of the front axle assembly is tranfserred to the body through the control arm mounts to the frame, the further back the mounts are the less effect the front axle weight has to work/pull down on the front of the rig. Of course, if the shocks are fully extended the weight will transfer through the shocks, but if you're nose is pointing upward and the shocks are fully extended you are already feeling the effects of unloading. A limiting strap can be used to transfer the weight of the axle assembly to the body at a much more forward location, and limiting straps work well to decrease unloading and to increase steep climbing ability. However, a balance has to be reached in determining the length of the limiting straps between axle articulation, climbing, and flat out runnning through the desert. Ideally, there would be three available limiting strap lengths, short for climbing, longer for articulation, and longest for the most travel when running flat out. Unfortunately, there's no real way to do that, so we have to compromise. Some competition rigs deal with this issue by using limiting straps set for trail work, and then use the winch attached to the front axle to pull down on steep climbs.

BTW, if a lift kit does not say "long arm", it's a short arm kit.

 

[Neil]

long arms are radius arms that force the axle to follow an arc (except for full traction's). with short arms you can get the axle to follow a straight up and down line. long arms should increase travel, especially compared with an uncut lca bracket, like was said before, becase the relative angles are decreased. radius arms will probably increase bump steer because they do get rid of the inherent advantage of the 4 link setup. it does seem weird to me to change to long arms for travel only to limit it with straps. IMO drop brackets with 4 link retained is the way to go, unless you have money to spare. with enough money you can have longer arms, longer shocks, good geometry and all that stuff. on my budget you cut the fenders and get some body damage.

When you get around 6" of lift the front axle will travel backward when it drops with short arms, with radius arms it will travel more of an arc. Radus arms and long arms have nothing to do with bump steer. bump steer is caused by changing angles in your tie rod and drag link.

Neil

 

[PapaPump]

so you are saying that having you steering knuckle axis tilted far from vertical during suspension cycling won't increase bump steer? seems to me it would wreak all kinds of havoc on steering feedback. ford TTB setups are notorious for bumpsteer because of the drastic changes in castor and camber throughout the suspension cycling. of course the steering setup can be very much to blame for this too. many bumpsteer problems can be solved with an idler arm setup in the fords, but not completely.

 

[XJ_ranger]

so you are saying that having you steering knuckle axis tilted far from vertical during suspension cycling won't increase bump steer? seems to me it would wreak all kinds of havoc on steering feedback. ford TTB setups are notorious for bumpsteer because of the drastic changes in castor and camber throughout the suspension cycling. of course the steering setup can be very much to blame for this too. many bumpsteer problems can be solved with an idler arm setup in the fords, but not completely.

the ford ttb set up is refered to as the dual wishbone setup, and is completely different than the XJ. The wheel cycles up and down and the arc is from the SIDE not the back. And it is an IFS setup, so a real tie rod wasnt used, but a tie rod that flexed in the middle. I had one and man it was fun in the mud... Camber changes all the time when TTB setups flex, and so does castor, but Ford suspention is so unrelated to Cherokee suspention, i dont even want to think anymore....

 

[ArcticXJ]

I ran 6" of lift on short arm RE super flex's and drop brackets for a year+. I recently upgraded to a full long arm setup, and currently sit at roughly 11" over stock suspension height, and wonder sometimes how i could even stand the shortams. Granted, when set up correctly (i.e. brake lines, shocks, e-brake cable etc.) short arm/ drop bracket systems can perform exceptionally well up to about 6" of lift. However, in order to appreciate the functionality of a well built longarm system, I had to get out and put one through its' paces myself. It honestly is a night and day difference in the ride, articulation, stability, and suppleness when switching between the two. I am very very pleased with the suspension now, and dont plan on making any further adjustments to it. IMHO, the longarm is the way to go if youre serious about your Cherokee's performance, and plan on running anything more than 35's.