3 Critical Shim Mistakes: The Unspoken Dangers of Corrective Saddle Pads

Your saddle sits a little low in the back. A friend suggests a corrective pad with rear shims. You slide them into the pockets, tack up, and suddenly, everything feels level. Problem solved, right?

Maybe not. While saddle shims and corrective pads seem like a simple fix, they’re one of the most misunderstood tools in the equestrian world. Used correctly, they can be a temporary bridge to better balance. But used incorrectly, they can create new pressure points, restrict movement, and mask serious fit issues—trading one problem for another.

This guide is for any rider who has ever reached for a shim to solve a saddle fit puzzle. We’ll explore the simple physics behind how they work, the common mistakes to avoid, and why true comfort often lies in addressing the root cause, not just the symptom. Understanding these principles is a critical step in your journey toward better saddle fit basics.

The Goal Isn’t Lifting, It’s Balancing: The Physics of Saddle Pressure

The first ‘aha moment’ in understanding shims is realizing their job isn’t simply to ‘lift’ a part of the saddle. Their real purpose is to redistribute the rider’s weight to achieve even pressure across the horse’s back.

Think of a perfectly fitting saddle as leaving a uniform, light handprint across the supportive muscles on either side of the spine. When a saddle is out of balance—perhaps tipping forward or backward—that handprint becomes uneven, with heavy pressure in some areas and little to no contact in others.

Research confirms what experienced fitters have known for years: shims are a temporary measure to correct minor imbalances, often while a horse is developing muscle. They aren’t a permanent fix for a saddle that fundamentally doesn’t fit the horse’s shape. When you add a shim, you’re not just adding padding; you’re changing the entire dynamic of how the saddle tree interacts with your horse’s back.

A Guide to the Shim Toolkit: Front, Middle, and Rear

Most corrective pads come with pockets for shims in three key areas: front, middle, and rear. Each one is designed to address a very specific issue.

When to Consider Front Shims

Front shims are most commonly used to address a temporary loss of muscle behind the withers. This often creates hollows, causing the front of the saddle to drop.

• Correct Use: To fill these hollows and provide a stable base for the front of the saddle, preventing it from tipping forward. This is often a temporary solution used as a horse builds up their topline through correct work.
• The Critical Mistake: Using front shims to ‘fix’ a saddle that is too wide. While this might feel more stable to the rider, it narrows the gullet channel and can severely pinch the horse’s withers and trapezius muscle. This compromises essential shoulder freedom and can cause pain and resistance.

When to Consider Rear Shims

Rear shims are often reached for when a saddle appears to be sitting ‘downhill,’ or lower at the back than at the front.

• Correct Use: To lift the back of the saddle slightly, rebalancing the rider’s position over the horse’s center of gravity. This might be needed for a horse with high withers and a strong, broad back.
• The Critical Mistake: Over-shimming the rear. This is where basic physics works against you. Adding too much lift at the back creates a pivot point, turning the saddle into a see-saw. Research has shown that this doesn’t just lift the back; it drives the front of the saddle down and forward, significantly increasing pressure under the stirrup bar area. You solve one problem only to create a more concentrated, painful one.

The Rarely Used Middle Shim

Middle shims are the least common and are intended to address ‘bridging,’ where the center of the saddle doesn’t make contact with the horse’s back—a problem often seen in horses with a swayback.

• Correct Use: To provide gentle support through the middle of the saddle panel, completing the ‘bridge’ and distributing weight more evenly.
• The Critical Mistake: Using a shim that is too hard or thick. This can create a focal point of intense pressure directly on the most sensitive part of the horse’s back, doing far more harm than good.

The Unspoken Dangers: When Shims Do More Harm Than Good

While well-intentioned, the misuse of shims can lead to significant biomechanical problems that aren’t immediately obvious to the rider.

The Bridging Effect: Creating a Tunnel of No Contact

The most severe consequence of over-shimming (especially at both the front and back) is creating a bridge. The saddle then makes contact only at the very front and very back of the panels, leaving a gap with no contact in the middle. This concentrates the rider’s entire weight onto four small patches, which can lead to soreness, muscle atrophy, and behavioral issues.

Chasing a Moving Target

A horse’s back is dynamic; it changes with fitness level, age, and even the season. Relying on a complex system of shims means you are constantly adjusting for these changes. This reactive approach can leave you one step behind, always trying to fix a problem that has already emerged rather than preventing it with an adaptable saddle. The risk is even greater for unique conformations like those of short-backed horses, where a small error in balance can have a big impact.

Masking the Real Problem

Perhaps the greatest danger is that a shim can make a saddle feel stable to you, the rider, while silently causing discomfort for your horse. It’s a band-aid that hides the underlying issue—a saddle tree or panel shape that is fundamentally wrong for your horse. True harmony can’t be achieved when your equipment is masking a silent problem.

The Smarter Alternative: Prioritizing Foundational Fit

Shims have their place as a diagnostic tool or a temporary support during a horse’s physical rehabilitation or development. But they aren’t, and were never meant to be, a long-term solution.

The most effective path to comfort and performance is to invest in a saddle with a design that inherently matches your horse’s biomechanics. Instead of adding and removing shims, the focus should be on a system that fits correctly from the start. Features like an adjustable tree and an intelligently shaped panel can provide the adaptability needed for a changing horse without creating the pressure points associated with shimming.

By focusing on the quality of your primary equipment, you move from a reactive cycle of problem-solving to a proactive foundation of comfort and balance. Exploring concepts like thoughtful saddle panel design is a great place to start on this more sustainable path.

Frequently Asked Questions (FAQ)

How do I know if I need shims?

The need for shims should be identified by a qualified, independent saddle fitter during a thorough evaluation. This isn’t a DIY diagnosis. They can determine if a temporary imbalance can be corrected with a shim while your horse’s musculature develops or changes.

Can I use more than one shim in a pocket?

This is generally not recommended. Stacking shims often creates hard, defined edges that can lead to severe pressure points. A single, well-shaped shim is almost always preferable.

What material should shims be made of?

High-density foam or felt are common choices because they can distribute pressure without compressing completely or creating hard edges. The goal is to find a material that integrates smoothly between the pad and the saddle.

My saddle is a little too wide. Can I use front shims to make it fit?

This is one of the most common and dangerous misuses of shims. While it may stop the saddle from rocking, it narrows the channel over the spine and can severely pinch the withers and restrict the horse’s essential shoulder movement. The saddle’s tree width must be correct from the start.

Your Next Step: From Temporary Fixes to Lasting Comfort

Shims are a nuanced tool, not a cure-all. They serve a purpose for temporary, subtle adjustments under professional guidance. But relying on them as a permanent fix means you may be missing the bigger picture of your horse’s comfort.

The ultimate goal for any rider is a saddle that fits so well it becomes a seamless interface for communication—no bumps, no bridges, no temporary fixes needed. By understanding the biomechanics of fit, you empower yourself to move beyond the cycle of correction and toward a foundation of true and lasting comfort for both you and your horse.