The various strength properties of a gearset are often due to the gear teeth and how they are driven. The actual design of the ring gear teeth is another complex idea. First, imagine that the gear tooth is a small model of a stadium with a curved shaped. The drive side would be the convex outside of the stadium with a nearly vertical wall. The coast side of the gear tooth would be the concave inside of the stadium where all the seats are and there is a more gradual angle from base to top. The drive side is the strongest portion of the gear tooth to have the pinion drive against.