Tendency of a ball hit on the toe or heel of the club (usually thought of in terms of woods) to spin in the opposite direction from the twisting of the club face.
The spin created by the bulge in a wood when the ball is struck near the toe or heel. If a ball is hit near the toe, the spin is counterclockwise. If the ball is hit near the heel, the spin is clockwise.
The effect that tends to cause a ball hit toward the toe or heel side of face center to curve back to the intended target line.
the fading or drawing of the ball back toward the fairway on miss-hits.
the effect caused by the convex face of a driver or wood that imparts a spin that reduces the amount of side spin imparted to the ball (see bulge and roll). In short it helps the ball go straighter.
unless the ball is hit directly in the centre of the club face, the head will rotate. This rotation of the head causes the gear effect which places unwanted spin on the golf ball.
The bulge on wooden clubs causes toe or heel hits to have reverse spin applied to the ball which reduces the hook or slice which would be much more pronounced if the face was flat. The term is also applied to irons and the "Gear Effect" comes from cavity back irons having more weight in the heel and toe.
