EXPERIENCE IS THE REASON
Experience is exactly the reason why DT Swiss has chosen not to use wheel building machines. Currently wheel building machines are simply not able to build a wheel of the same quality and in the same amount of time as by hand. This is because many factors come into play while truing a wheel which can vary from wheel to wheel. People learn these differences over the years and can differentiate and act as needed. Flexibility is another advantage of hand building. DT Swiss wheels are de-stressed several times per side during the wheel building process, until the changes in lateral and vertical deviations and spoke tension are within the desired tolerances. In machine production, these steps in between would lead to retooling effort during construction, which again cancels out the advantage of machine production. These steps are therefore often omitted in machine production but crucial for the quality.
SPOKE TENSION: THE HIDDEN FORCE
An essential factor that ensures the quality of a wheel is the spoke tension. It is this hidden force that makes a wheel durable, provides precise steering and gives the ability to accelerate. The art of wheel building is to set the spoke tension as close as possible to the given maximum, while keeping the deviation of the tensions between them as low as possible. Illustration 1 shows the spoke tensions of a rear wheel with 28 spokes. The black circle shows the tensions of the spokes on the right side (drive side) and the red curve shows the tension of the left side (non-drive side). Here it can be seen that individual tensions per side differ only minimally from one other.
Illustration 2 shows the tension of a wheel statically loaded with the weight of a rider. If the wheel is well and equally preloaded, the load is distributed to almost all spokes in the upper half of the wheel. The tension of the individual spokes increases there, while the tensions of a few spokes decreases slightly in the area of the contact patch. This means that during a wheel rotation, each spoke is maximally loaded and unloaded once. On a 29-inch wheel, This happens about 430 times on a one-kilometer-long track. If the preload is too low overall, this can lead to spokes being completely unloaded. As a result, the spokes can loosen further and are charged heavier. The wheel is more unstable overall and the material tires prematurely. On the other hand, if the tensions were too high at peak loads, e.g. In a landing after a jump, the force on the spoke would be too high and the spoke would plastically deform. This over-stretching of the spokes reduces the tensions, and the wheel loses stability.