Seam Shifted Wake effect (SSW) pitches create an area of low air pressure on one side of the ball and the ball moves towards that, being pushed by the relatively higher air pressure elsewhere around the ball. The low air pressure is generated when air passes over a lace that is positioned near the horizon. The low pressure is best formed when the lace is from 12 degrees on the leading edge to 8 degrees on the trailing edge. The longer the lace stays in the orientation the more air low pressure will be generated and more break will result.
SSW pitches rely on a precise placement of the seams as the ball travels towards the target. The 20 degree tolerance (the width of a seam is about 15 degrees) in the direction of the rotation can be measured by a system like Rapsodo and others. It can also be observed reasonably accurately using slow motion video on a phone. Either way the student will likely need to do some experimentation to get it just right.
The direction of the rotation is only part of the story. The orientation of the seams on the ball needs to wind up producing what is necessary to create the low pressure area. The seam that is best used is the long seam and the placement of that lace, resulting from both s[pin direction and how the ball is held, is critical as the ball travels. Placing the seam just over the horizon will maximize the effect. The rise ball is currently the most popular SSW pitch. The explanation below shows how critical the grip is.
While teaching a SSW pitch it is good to have a ball with a SSW tracking dot on it. This tracking can be drawn on the ball right in the middle of the C shaped seams. It will be where the axis or rotation goes through the ball exactly perpendicular to the spin on a 2 seam fastball. Getting that tracking dot to remain stationary is the key that unlocks any SSW pitch.
