The weight bearing part of the hoof is not limited to the hoof wall, but rather includes portions of the hoof wall, the sole, and the frog, sole callus, and the bars.

Flaring occurs when weight is placed only on the hoof wall; the hoof wall breaks down in order to allow the other portions of the hoof to support weight. This can be explained through the difference in forces exerted on the hoof wall between a hoof where solely the hoof wall supports the horse's weight and a hoof where all parts of the hoof serve to support the horses weight. The hoof on the right shows a good example of flaring, while that on the left has had the flares removed. Image from Maximum Hoof Power.

In certain gaits, all of the horse's weight is placed an the individual hoof at certain times, so the force exerted on the hoof will equal the horse's mass times the hoof acceleration. Regardless of the horse's weight and hoof acceleration, the force exerted per unit of area on the hoof wall is far greater when only the hoof wall supports the horse than when the hoof functions as a whole to support the horse.