Have you ever felt like you’re constantly shifting your weight in the saddle, or dismounted to find one side of your horse’s back is sweatier than the other?

You might dismiss it as just “one of those days,” but it could be a sign that your saddle isn’t sitting level. For many riders, the go-to solution is a corrective pad with shims.

It seems simple enough: find the low spot, add a shim, and solve the problem. But shimming is a science. Choosing the wrong placement—front, middle, or rear—can turn a potential solution into a new problem, creating pressure points and restricting movement.

If you’ve noticed your horse is a bit asymmetrical, you’re in good company. In fact, you’re observing the norm. A groundbreaking study by Greve and Dyson (2013) found that out of 506 seemingly sound horses, a staggering 97.2% had some form of locomotion abnormality or underlying lameness. Asymmetry is not the exception; it’s the rule. Understanding how to support it is the key to comfort and harmony.

Why Shimming is More Than Just “Padding”

Before we dive into where to place shims, we need to understand why we use them. The goal of a corrective shim isn’t to add cushioning; it’s to create a level and stable platform for the saddle on an uneven surface—your horse’s back. Think of it like putting a wedge under one leg of a wobbly table. You’re not changing the table; you’re adapting to the uneven floor.

This is where many well-intentioned riders go wrong. They reach for thick, plush pads, thinking more padding equals more comfort. But research on saddle pad thickness shows that while pads can reduce pressure, they can also make a well-fitting saddle dangerously tight, especially over the withers.

Corrective shimming, when done right, is the opposite of this “blanket” approach. It’s a precise, targeted intervention, and that precision is crucial: a 2020 study by Mackechnie-Guire et al. confirmed that while shims can effectively redistribute pressure, incorrect shimming can significantly increase peak pressure, creating new areas of pain and soreness.

The goal is always balance. The right shimming strategy allows the saddle to sit correctly, freeing up the horse’s back. Research from Meschan et al. (2020) highlights how saddle fit directly impacts the horse’s back movement (thoracolumbar kinematics), making a balanced saddle fundamental to performance.

Diagnosing the Asymmetry: Where is the “Hollow”?

To choose the right shimming strategy, you first need to become a detective. Your first step is to identify the “void” or “hollow” causing the saddle to sit out of balance. These hollows typically appear in one of three areas: the front, middle, or rear of the saddle.

Let’s explore the common reasons for imbalance in each zone and how the correct shimming can restore equilibrium.

The Case for Front Shims: Addressing the Shoulders

This is the most common area requiring support, especially for horses with prominent withers or those lacking muscle behind their shoulder blades.

The Problem: Muscle atrophy behind the scapula is extremely common. This creates a “hollow” that the front of the saddle can collapse into. You might also see this in horses with high, narrow withers that lack muscle on either side.

The Symptom: Your saddle constantly tips forward, putting pressure on the withers and shoulders. You may feel like you’re fighting to keep your leg underneath you, falling into a “chair seat.” The back of the saddle may even lift slightly off the horse’s back when you’re in the stirrups.

The Solution: Front shims fill the empty space behind the shoulders. By inserting shims into the front pockets of a corrective pad, you lift the front of the saddle and prevent it from collapsing into the hollows. This levels the saddle, re-centers your weight, and frees up the horse’s shoulders to move—a crucial step when fitting saddles for many asymmetrical horses.

The Case for Middle Shims: Supporting the Center

Middle shims are less common but can be a critical tool for horses with certain conformations or a temporary loss of topline condition.

The Problem: The issue often stems from a horse with a “dipped” or swayback conformation, or one that has lost the muscle tone that normally supports the middle of the back. This causes the center of the saddle panels to lose contact with the horse.

The Symptom: This is known as “bridging.” The saddle makes contact at the front (pommel) and the back (cantle), but there’s a gap in the middle. All the rider’s weight is concentrated on those two small spots, creating immense pressure and preventing the horse from lifting its back properly.

The Solution: Middle shims fill the gap, providing support through the center of the saddle. This distributes the rider’s weight along the entire length of the panel, eliminating the painful pressure points caused by bridging. Keep in mind, however, that severe bridging can also be a sign of a saddle tree that is the wrong shape for your horse. Shims should be seen as a supportive tool, not a fix for a fundamentally incompatible saddle.

The Case for Rear Shims: Lifting the Back

This scenario is common in young, developing horses or those with an “uphill” build where the croup is significantly higher than the withers.

The Problem: The horse’s back rises sharply towards the croup, causing the saddle to tilt downhill towards the front. This can also happen with horses that have underdeveloped loin muscles.

The Symptom: The saddle feels low in the back and high in the front. The rider’s weight is shifted onto the back of the panels, creating pressure over the sensitive loin area. Riders often feel like they are being tipped forward and struggle to sit deeply in the saddle.

The Solution: Rear shims lift the back of the saddle, leveling the seat for the rider and shifting the pressure off the loins. This restores a correct, balanced position, allowing the rider to communicate more effectively and freeing the horse to move without discomfort.

The Golden Rule of Shimming: Less is More

The goal of shimming is to achieve balance using the thinnest shim possible. The temptation is to overcorrect, but as research shows, over-shimming creates new high-pressure zones. Start with a thin shim and check the balance. If it’s still not level, you can try a slightly thicker one.

A balanced saddle is a quiet partner in your horse’s training. It allows for gradual muscle growth, leading to better topline development, which in turn may reduce or even eliminate the need for shims over time. This principle of dynamic, precise adjustment has also led some saddle makers to explore innovative panel designs that can be expertly fitted to the horse, often reducing the need for temporary pad solutions.

Frequently Asked Questions (FAQ)

Should I shim on one side or both?

It depends entirely on your horse’s specific asymmetry. If one shoulder hollow is significantly deeper than the other, you may need a thicker shim on that side, or even a shim on one side only. The goal is to make the saddle level, which may require asymmetrical shimming on an asymmetrical horse.

How do I know if I’ve used the right shim?

First, check the saddle’s balance on the horse’s back without a girth. It shouldn’t rock excessively. Then, girth up and have a rider sit in it. The lowest point of the seat should be level. After a ride, look for broad, even sweat patterns. Most importantly, pay attention to your horse. Increased comfort, willingness to move forward, and freedom of movement are the best indicators.

Can shims fix a saddle that’s too wide or too narrow?

No. This is one of the most dangerous misconceptions about shimming. Shims are designed to fill in hollows or concavities on the horse’s back. They cannot correct a saddle tree that is the wrong angle or width. Using front shims to “fix” a too-wide saddle will pinch the withers and cause pain.

How often should I re-evaluate my shimming?

A horse’s back can change dramatically with age, training, and season. You should reassess your shimming strategy every 3-6 months, or anytime you notice a significant change in your horse’s body condition or way of going.

The Goal: A Balanced Saddle for a Balanced Horse

Corrective shimming is a powerful tool when used with knowledge and precision. It’s not about masking a poor fit, but about creating harmony between three dynamic elements: the horse, the saddle, and the rider.

Learning to see the subtle hollows and imbalances in your horse’s back lets you move from guessing to making informed decisions. Your journey starts with observation. Take a moment to look at your horse’s back, feel how your saddle sits, and trust what your horse’s behavior is telling you. Understanding the science behind shimming is the first step toward providing lasting comfort and building a stronger partnership.

To learn more about identifying these issues, explore our complete guide to saddle fit for asymmetrical horses.