Here is a T-6 doing a ground loop
Here’s what I’ve been told by one IA about toe-in / toe-out, that makes sense to me.
Consider a plane with toe-in, and assume the plane is traveling in a straight line, with equal weight on each tire. Assume that each tire toes in an equal amount as measured from the airplane’s center line. Because the tires are not parallel, each tire is skidding sideways some. Because there is equal weight and the the geometry is symmetrical each tire skids equally.
Now consider the same aircraft, in a left turn, and with the same toe-in. As it turns, it tends to lean to the outside of the turn, i.e. to the right. As it leans to the right the right-hand tire will now bear more of the plane’s weight than the left-hand tire. Now, because the right-hand tire is bearing more weight it will skid sideways less than the left-hand tire. Because it skids less, it’s toe-in acts with more authority on the plane, tending to steer it to the left, tightening the turn. Toe-in therefore results in decreased directional stability, tending to increase the taildragger’s inherent instability in a turn.
Now consider the same aircraft in the same left turn, but now with the tires toed out. Again, the right-hand tire is skidding less and has more toe-out authority than the left-hand tire, tending to steer the plane to the right. Toe-out therefore results in increased directional stability, in other words, tending to reduce the taildragger’s inherent instability in a turn.
Bottom line, toe-out tends to increase directional stability, while toe-in tends to reduce directional stability.