Since our main focus is towards their use in an ATV, this article deals with the pros and cons of both the joints in an ATV. For those who have no idea about these two joints, the pictures below shall feed their brains.
Ball joints are strong up and down but have limited angular movement. The ball and socket joint in human body that connects our leg bone to your hipbone, so goes the ball and socket joint that holds the front suspension of your vehicle together. Your leg can move up and down, and side to side, the automotive ball joint enables the wheel and suspension to move together in the same manner. If you try to increase the angular movement, it may result it in weakening the joints to pull-out force since the cup doesn’t cover the ball’s neck area much. These require very less maintenance. They last longer and are cheaper than their counterpart. Most often well sealed Tie rod ends are used as ball joints. They have high serviceability but the Z-axis force is still less. These may also have springs under the cup to take up wear. This makes them good to use for tie rod ends but poor for ball joints.
Heim joints are known to be a little weaker, but with the correct offset spacers, they can reach much farther angles than ball joint. Camber/caster adjustments are relatively easier. Using it may be a boon/ curse as it depends on the accuracy of the suspension design. But perpendicular to the shafts (Z axis) they are comparatively weak. With boots, Heim are reliable. But without it, grits get into them and wears out easily.
To summarize, the heim joints shall be used where end to end use, serviceability is preferred and the
Ball joints shall be used where strength, low maintenance and life is given the first preference.