Everything begins with the saddle tree. It’s the foundation for the saddle; the frame upon which everything else is built. Without a proper fitting tree, you’ll never have a good fitting saddle.
Horse backs are like snowflakes, no two are the same. The job of the saddle tree is to distribute the rider’s weight over the horse’s back, making it more efficient and comfortable for the horse. A tree consists of four basic parts: two bars that run parallel, the fork (pommel) that holds the bars together at the front, and the cantle that holds the bars together in the back. The gullet runs down the center underneath making room for the withers, spine and ligaments.
To distribute weight evenly, the entire length of the bars must be in even contact with the horse’s back. The gullet channel between the bars must be wide enough to keep pressure off the spine, then widen at the front to accommodate the withers and shoulders. The bars of the saddle tree are the actual weight-bearing surface of the saddle, the part that’s in contact with the horse. Well-fitting bars of a western saddle will apply only 3/4 lbs per square inch to the horse’s back with a 150 lb rider up. In contrast, an English saddle, which has less surface area, will apply about 1 3/4 lbs per square inch.
How well a saddle tree will fit a horse’s back is determined by the shape of the bars. There are three main areas to consider:
The rocker follows the curve of the horse’s back where the center of the tree bar should lie when placed on the horse’s back; about 4 inches off either side of the spine. (Rock is shown in the “Twist” picture and the “Rock in Bar” picture by the long arrows). Get the rock wrong and you get a tree that either applies pressure in a small area usually near the front or a bridging tree that applies pressure at the bar ends, front and back.
Relief at the front and back ends of the bars is especially important. A lot of curve over that last inch will relieve the pressure as it comes up to the shoulder giving it a gradual transition and allowing the horse’s shoulder to move freely underneath the saddle.
The width and angle of the horse’s back changes all along the back, from the steeper and wider angels around the withers to the flatter angles at the rear of the saddle. Get these angles and widths wrong in any place along the back and you create tight spots or bridges. (Angles are shown in “Twist” picture) Most saddle makers use one measurement at the front of the bars to determine the size of tree; it’s kind of like buying a pair of pants by measuring your thigh.
The transition point of the tree from horizontal to vertical pressure coincides with the attachment point for the Thoracic Trapezius and Latissimus Dorsi muscles in the wither area. Saddle pressure on the attachment points can cause shortened stride and behavioural issues. These muscle will enlarge with work and a saddle that fit to start becomes too tight as in our top image.
Easy Fit Saddles’ custom trees are made to measure, allow room to grow and are shimmable to keep them fitting.