A saddle that is too wide in the tree will:

When a saddle has a tree that is too wide for the horse's back, it will not sit properly in relation to the horse's anatomy. Specifically, a wide tree will cause the saddle to sink down toward the horse's withers. This occurs because the saddle does not have adequate contact with the horse's back, leading to an imbalance where the front of the saddle dips lower.

This improper fit can create discomfort for the horse, as it may not distribute the rider's weight evenly and can interfere with the horse's natural movement. Additionally, the malalignment can result in pressure points that cause pain. Therefore, ensuring that the saddle tree fits correctly for the individual horse is crucial for the comfort and performance of both the horse and rider.