Wheelbuilding

Wheelbuilding is the process of assembling wire wheels (generally a bicycle wheel, but including wheelchairs, and some cars). The components of a wire wheel are the rim, spokes, nipples, and hub.

The wheelwright must ensure that the wheel is true in two ways: lateral (sideways wobble) and radial (roundness/hop). The wheel also needs to be properly dished if applicable (the left and right sides of the rear wheel differ, the drive-side spokes requiring higher tension). Spokes should have no residual twist (windup) from tightening the nipples. The spokes may be "stress relieved", i.e. subjected to a greater tension during building than they are ever likely to encounter in use - usually by squeezing pairs of spokes together very hard. This 'yields' the spokes (and/or the hub) into a permanent shape where they bend around the hub flanges and each other.

Spoking patterns may be or semi-tangential. For a normal wheel size and spoke count, only the latter is suitable for a wheel that has to transmit torque from the hub to the rim, as with rear wheels or hub brakes. This rule is occasionally broken where a very large number of spokes is used or the wheel is unusually small in diameter, either of which reduces the amount of increased tensile stress on each radial spoke to an acceptable degree; some BMX bicycles and low-riders use radial spoking for both wheels. Rear wheels may also incorporate radial spoking on the non-drive side and semi-tangential spoking on the drive side. At least one example, the Mavic Ksyrium, has radial spoking on the drive side of the rear wheel.

The most common spoking pattern is "three-cross" where each spoke crosses three others on the same flange of the hub before meeting the rim. The last cross is normally "interlaced" by wrapping the spoke around the one from the other side of the flange. Radial-spoked wheels, where the spokes do not cross each other, saves roughly the weight of two spokes (because the spokes are shorter) compared to a three-cross wheel but run an increased risk of cracking at the hub flange, unless the hub is specifically designed for this pattern. Two-cross is sometimes used for hubs with large-diameter flanges (such as generator/dynamo hubs or large flange hubs), as it gives a more perpendicular spoke/rim angle, and four-cross is standard for spoke counts of 40 and above.

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Wikipedia