Wire wheel 6 rigid spokes began to appear in the Olympic Games and professional racing: these have advantages in specialized applications, such as time trials, but wire-spoked wheels are used for most purposes. The reaction to a radial load of a well-tensioned wire spoked wheel, such as by a rider sitting on a bicycle, is that the wheel flattens slightly near the ground contact area. The rest of the wheel remains approximately circular. The tension of all the spokes does not increase significantly. Instead, only the spokes directly under the hub decrease their tension. The issue of how best to describe this
Reaction wheel temporary changes in its speed result in small changes in angle. The wheels therefore permit very precise changes in a spacecraft's attitude. For this reason, reaction wheels are often used to aim spacecraft carrying cameras or telescopes. Over time, reaction wheels may build up enough stored momentum to exceed the maximum speed of the wheel, called saturation, which will need to be cancelled. Designers therefore supplement reaction wheel systems with other attitude control mechanisms. In the presence of a magnetic field (as in low Earth orbit), a spacecraft can employ magnetorquers (better known as torque rods) to transfer angular momentum