What's the difference between long arms and short arms?

 

Length.

I'm sorry, had to.

I'm pretty sure it's to adjust the position of the axle when lifting. If you lift with stock arms, the axle will pull inwards towards the centre of the vehicle. By increasing the arm length you can push the axle back into the centre of the wheel arch.

 

Short arms mount in the factory location. A long arm kit has its own brackets that mount further back, and the upper and lower control arms are attached at the same point.

 

yes but what's the benefit of a longer arm? Like you would think a shorter arm would have more strength

 

More suspension travel and a better ride if you have a big lift.

 

They keep the angle of the arms similar to factory when you've added a tall lift. If you have short arms and a big lift, the control arms come down from the body at a steeper angle and this makes for a harsher ride. Imagine hitting a bump when driving forwards and the direction of the force is almost straight along the arm to the mount - it's going to be harsh. As the arm moves more parallel to the ground, the force is hitting at a greater angle to the arm which pushes the arm up and then the force is absorbed by the spring and shock instead of the LCA mount and the unibody.

 

Perfect explanation thanks

 

They hang up on rocks better too. Offroad TJ guys avoid them at all costs.
p.s. My XJ on short arms rides better than stock,

 

I'm no expert, but I don't think that's true about avoiding longarms. Unless it's something specific with TJs.