All bicycle spokes have two distinct ends, one is hooked and the other threaded. The hooked end attaches to the wheel's hub and the threaded end is fitted to a small nut that holds the spoke to the wheel's rim. When building a wheel, spokes must have adequate tension to hold everything in place. To achieve that tension and keep it there, you must also consider spoke torque.
Torque
The only part of a wheel that should have torque applied to it is the spoke nut, which screws onto the spoke from inside the rim. The spokes themselves should ideally have no torque applied to them, also known as torsion. If a spoke has torsion when the wheel is built, it causes problems. As the spoke untwists while you ride, the wheel becomes untrue. An untrue wheel is one in which the hub is not perfectly centered in the middle of the rim.
Tension
Although spokes should never have a torque force, all spokes have tension. Tension is the amount of force on the spoke when holding the wheel to the hub. Each wheel manufacturer specifies an ideal spoke tension which is dependent on the size and material of the wheel, as well as the size and material of the spokes. The goal is to have all spokes at the same tension.
Truing
Truing is the practice of centering a hub in a wheel's rim by altering the tension of the spokes. By applying torque to the spoke nuts with a spoke wrench, you can increase the tension in the spoke and align the wheel better. Since truing is most accurately guided by the tension of the spoke, rather than the torque force used to tighten them, manufacturers do not specify a torque force. As such, no specific amount of torque should be applied to any spoke.
Considerations
Spoke torsion can be avoided tow ways when applying torque to the spoke's nut and increasing tension. Your first option is to counteract the buildup of spoke torsion by torquing the spoke nut slightly tighter than necessary and then releasing the torque by untwisting it. This practice of twisting and untwisting should help prevent spoke torsion. You may also consider a spoke grip tool that holds the spoke in place while you tighten it, preventing spoke torsion.
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