short arms and long arms!
01-16-2011, 05:23 AM
#3
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Factory is short arm. A long arm kit uses longer control arms which give you less caster and pinion angle fluctuation while flexing. It is most beneficial for high speed applications. That is why prerunners always use long arms. Long arms are a must for Baja and desert racing. For rock crawling, long arms allow for more flex and articulation. That is the short explanation, someone else can expand on it.
and one more thing, what is the difference between the front lower arm And the upper arm??
01-16-2011, 10:27 AM
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One set is lower than the other? (or above the other, depending on which way you are looking at them?) 
Uppers attach from the frame to the top of the axle. Lowers attach from the frame to the bottom of the axle. When you get adjustable arms, they are used to 'tilt' the axle to improve caster and pinion angles. Either set will do the job, but front lowers and rear uppers are the better choices if you only get one set per axle.
Front uppers:
Lengthen to lower caster
Shorten to increase caster
Front lowers:
Shorten to lower caster
Lengthen to increase caster
Uppers attach from the frame to the top of the axle. Lowers attach from the frame to the bottom of the axle. When you get adjustable arms, they are used to 'tilt' the axle to improve caster and pinion angles. Either set will do the job, but front lowers and rear uppers are the better choices if you only get one set per axle.
Front uppers:
Lengthen to lower caster
Shorten to increase caster
Front lowers:
Shorten to lower caster
Lengthen to increase caster
Last edited by nthinuf; 01-16-2011 at 10:30 AM.
01-16-2011, 10:32 AM
#6
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Originally Posted by nthinuf
One set is lower than the other? (or above the other, depending on which way you are looking at them?)
Uppers attach from the frame to the top of the axle. Lowers attach from the frame to the bottom of the axle. When you get adjustable arms, they are used to 'tilt' the axle to improve caster and pinion angles. Either set will do the job, but front lowers and rear uppers are the better choices if you only get one set per axle.
Uppers attach from the frame to the top of the axle. Lowers attach from the frame to the bottom of the axle. When you get adjustable arms, they are used to 'tilt' the axle to improve caster and pinion angles. Either set will do the job, but front lowers and rear uppers are the better choices if you only get one set per axle.
01-16-2011, 11:25 AM
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Long arms are going to put your control arms at a more optimal angle for better bump absorption. Whenever you lift a vehicle, the wheels will move towards the center of the vehicle. On the rear, this is not a big issue if you leave pinion angle out of the equation. Since it is a trailing arm, a would be bump contact the wheel and lifts it upwards. As long as the rear angle was not 100% vertical, the control arm just swings upward. Provided you are going forward.
On the front it is a different story, As the wheels move towards the rear of the vehicle when you lift it, the control arm angle becomes steeper. When the front tire contacts a bump, it meets a bit of some force as the control arm is pointing down. The more level the control arm is with the frame of the vehicle, the less force it takes to move the wheel upwards to overcome a bump it the road.
The bracket that comes with long arms is designed in such a fashion that it puts your control arms at the original or close to original angle your stock control arms were at to begin with before you lifted it. Ideally, it should be close to parallel with the ground.
Since the control arm is now placed closer to parallel, it will also provide more articulation as the control arm is not already moved to the end of its travel limits.
Depending on how you drive your rig, you may or may not really need these but they are always better to have over the short arms.
On the front it is a different story, As the wheels move towards the rear of the vehicle when you lift it, the control arm angle becomes steeper. When the front tire contacts a bump, it meets a bit of some force as the control arm is pointing down. The more level the control arm is with the frame of the vehicle, the less force it takes to move the wheel upwards to overcome a bump it the road.
The bracket that comes with long arms is designed in such a fashion that it puts your control arms at the original or close to original angle your stock control arms were at to begin with before you lifted it. Ideally, it should be close to parallel with the ground.
Since the control arm is now placed closer to parallel, it will also provide more articulation as the control arm is not already moved to the end of its travel limits.
Depending on how you drive your rig, you may or may not really need these but they are always better to have over the short arms.
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01-16-2011, 12:15 PM
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Up front:
After the lift, your caster is low and will cause flightier handling. To raise caster, (lower the pinion), you need to tilt the top of the axle back (shorten the uppers), or tilt the bottom of the axle forward (lengthen the lowers). A lot (most) of the adj uppers may not adjust short enough to get the caster where you want it.
In back:
With the stock driveshaft and a lower lift height, you may not need to adjust, but with an aftermarket driveshaft you will want to tilt the pinion up. Uppers will be lengthened, lowers would be shortened. And while minimal, shortening the lowers will also shorten the wheelbase a bit more and bring those rear tires closer to the pinch seam...
01-18-2011, 06:20 AM
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One set of adj arms per axle will let you set the caster/pinion. The second set of arms will let you fine tune, and also lets you move the entire axle forward/backward in the wheel well. (as you lift higher, the axles move. Front goes toward the rear, rear axle moves forward. This shortens the wheelbase, and can cause issues with the rear tires rubbing the rails/pinch seam, etc.)
Up front:
After the lift, your caster is low and will cause flightier handling. To raise caster, (lower the pinion), you need to tilt the top of the axle back (shorten the uppers), or tilt the bottom of the axle forward (lengthen the lowers). A lot (most) of the adj uppers may not adjust short enough to get the caster where you want it.
In back:
With the stock driveshaft and a lower lift height, you may not need to adjust, but with an aftermarket driveshaft you will want to tilt the pinion up. Uppers will be lengthened, lowers would be shortened. And while minimal, shortening the lowers will also shorten the wheelbase a bit more and bring those rear tires closer to the pinch seam...
Up front:
After the lift, your caster is low and will cause flightier handling. To raise caster, (lower the pinion), you need to tilt the top of the axle back (shorten the uppers), or tilt the bottom of the axle forward (lengthen the lowers). A lot (most) of the adj uppers may not adjust short enough to get the caster where you want it.
In back:
With the stock driveshaft and a lower lift height, you may not need to adjust, but with an aftermarket driveshaft you will want to tilt the pinion up. Uppers will be lengthened, lowers would be shortened. And while minimal, shortening the lowers will also shorten the wheelbase a bit more and bring those rear tires closer to the pinch seam...
I am looking to lift my JK in the next 3 weeks and am considering adjustable lower front arms, to start. I think, for my budget and driving style and what we use our JK for, the short arms are going to get the nod. Maybe someday I can go all out..... oh I can still dream! Thanks guys
01-18-2011, 07:22 AM
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I love mine. My friend had a 4" Full Traction SA. I rode and drove his prior to getting mine. Big difference. My ride on the road is far superior. I had not thought about the way the bumps affected front and rear axles differently, so I just learned something. Here in Alabama, the roads get kindof ruddy in the summer because they build such crappy roads. Some of this is in turns, so I can see how more compliant suspension is benificial on the roads. I can't say that the extra money paid is worth the little bit of articulation you gain. After having a LA kit, I would never want to go back to a SA, but cash would definitly play a huge roll in that decision. My LA is actually a huge reason I won't trade my 2 dr for a 4.
About $1200 - $2000
Bragging Rights!
The JK already has long arms compared to the TJ.
Those who have long arms will say the ride is better. I rode and drove a long arm before I bought my TERAFLEX lift, and to be honest, I can't tell a difference in ride quality.
With the cutting off factory parts and welding on new mounts and longer arms to drag over obstacles, I couldn't see getting long arms. Mine rides great!
Bragging Rights!
The JK already has long arms compared to the TJ.
Those who have long arms will say the ride is better. I rode and drove a long arm before I bought my TERAFLEX lift, and to be honest, I can't tell a difference in ride quality.
With the cutting off factory parts and welding on new mounts and longer arms to drag over obstacles, I couldn't see getting long arms. Mine rides great!