Tests the horizontal stiffness of the rim when a weight is applied to side of a horizontal rim.
The bottom half of the wheel is secured into a fixture in a horizontal position. Pressure is then applied in a horizontal plane (load position is beside the valve) to the center of the top half, and deformation is measured.
While some horizontal flex is inevitable and necessary, a horizontally stiffer wheel will enhance the wheel’s performance, especially when torqued during a sprint or during a hard corner.