The strength of spoke lacing
Spokes made of thin wire are much stronger tension-wise than in compression. The rim, on the other hand, is quite pressure-stable. Tension spokes experience an elastic change in length while in use. That is why the spokes must be pretensioned enough to allow the system to compensate for short-term stretching. The spokes relieved at the lower part must not lift off from the rim base. Such loosening and re-tensioning would cause a notch effect between spoke bend and hub flange – and weaken the spoke at this point. For this reason, the preload must be as high and as uniform as possible. With sufficient pre-tensioning of all spokes, peak loads during sprints, jumps and full braking actions are distributed evenly over all spokes. Nevertheless, try not to go overboard with spoke tension. Carbon fibre rims in particular are somewhat sensitive in this regard during assembly, and are more likely to break than bend. So be sure to follow the manufacturer's instructions for hubs, nipples, spokes and rims, and use a tensiometer if in doubt, but especially if you are lacing carbon rims. Theoretically, the connection between spoke and rim makes the perpendicular wheel stable in itself, so that it can absorb vertical forces. In reality, however, the wheel must also withstand extreme torsional and lateral forces. The absorption of these forces is ensured by at least two hub flanges. The support on both sides results in the angle of the spoke discs, and can absorb high forces – comparable, for example, to the mast of a sail boat, which is held in place laterally by pre-tensioned shrouds. If one spoke breaks, the other spokes are initially able to compensate for the forces that occur. In the long run, however, this can lead to overloading of the neighbouring spokes, which is why the damaged spoke should be replaced as soon as possible.