7 Best Stainless Steel Shim Kits For Leveling Slide-Out Tracks

Nothing ruins the serenity of a remote boondocking spot quite like the agonizing screech of a slide-out grinding against its track. Leveling these heavy components is a critical maintenance task, yet many owners ignore the subtle warning signs until mechanical failure sets in. Selecting the right stainless steel shim kit is the difference between a smooth, whisper-quiet extension and an expensive repair bill at the service shop.

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Precision Brand Slotted Shim Kit: Best Overall

When it comes to universal reliability, the Precision Brand slotted shim kit remains the industry gold standard. These shims come pre-cut in various thicknesses, allowing for rapid adjustments without the need for manual trimming or complex geometry work. Because they are manufactured from high-quality 300-series stainless steel, they resist corrosion even in harsh, humid coastal environments.

The “slotted” design is the real game-changer here, as it allows the shim to slide behind a bolt or fastener without requiring a full removal of the hardware. This saves hours of labor during a project where space is restricted by tight slide-out fascias. For anyone seeking a balanced, professional-grade solution that works on nearly every RV or mobile home rail system, this is the definitive choice.

Uxcell 304 Shim Stock Roll: Best for Custom Cuts

If the slide-out track has an irregular contour or a non-standard gap that a pre-cut shim cannot address, a shim stock roll is the only practical solution. Uxcell’s 304 stainless steel offers excellent tensile strength and corrosion resistance, ensuring that once it is placed, it stays put under the weight of the slide. It requires a decent set of metal shears, but the trade-off is total control over the exact shape of the material.

This option is ideal for the experienced DIYer who prefers to create custom-tailored wedges rather than forcing a standardized part into a tight space. While it requires more patience during the measurement and cutting phase, the final fit will be far superior to anything generic. Choose this roll if precision and customization are prioritized over the speed of installation.

McMaster-Carr Slotted Shim Pack: For the Pros

McMaster-Carr is a legendary name in industrial engineering, and their shim packs carry that same reputation for uncompromising quality. These shims are machined with incredible tolerance, meaning a .005-inch shim is exactly what you get, not a rough approximation. This level of consistency is vital when aligning a high-end slide-out system where even a fraction of an inch can cause a binding gear or a leaking seal.

This choice is specifically recommended for those dealing with precision-engineered tracks that have very little margin for error. If the equipment is top-tier and requires meticulous, repeatable results, bypass the budget kits and invest in these. It is the professional’s preference because it eliminates the guesswork associated with manufacturing variances.

Trinity Brand Slotted Shims: Premium Durability

Trinity Brand shims are built for owners who expect their repair work to outlast the vehicle itself. These shims are hardened and finished to prevent galling, a process where metal surfaces weld together under friction or pressure. By using these on high-load tracks, you significantly reduce the risk of the shim deforming or “creeping” out of place over time.

They are particularly effective in environments where the slide-out faces frequent deployment and retraction, such as full-time living setups. The added hardness makes them slightly harder to manipulate but provides peace of mind that the leveling will remain stable for years. If durability is the primary concern, Trinity provides the most robust path forward.

AccuTrex Variety Pack: Widest Size Selection

Sometimes the scope of the problem is unknown until the track is partially disassembled. The AccuTrex variety pack solves this by providing a massive range of thicknesses in a single kit, covering almost every conceivable gap size. Instead of buying individual packs, you get a comprehensive library that allows for “stacking” or finding the perfect single-shim fit on the fly.

This pack is the best insurance policy for those who don’t want to make multiple trips to the hardware store or wait on shipping for a different size. While you may have leftover parts, the versatility of having the exact thickness needed right in your hand is invaluable. It is the practical choice for anyone performing a total system overhaul.

Fastenal Assorted Shims: Easiest Local Pickup

Fastenal is the go-to resource when a project needs to happen immediately. Their assorted shim kits are widely available and offer a reliable balance of steel grade and thickness options. While these kits may not have the extreme specialized tolerances of an industrial supplier, they are more than adequate for the vast majority of residential slide-out leveling needs.

These are best for the weekend warrior who identifies a track issue on a Saturday morning and needs a solution by the afternoon. Because they are available through local distribution channels, you avoid the downtime of waiting for online shipping. They provide a solid, serviceable fix that gets the rig back in working order with minimal effort.

W.M. Berg Shim Stock Kit: Engineering Grade Pick

W.M. Berg specializes in high-precision components, and their shim kits reflect a commitment to engineering-grade specifications. These shims are manufactured with exacting standards for flatness and parallelism, ensuring that when the track is shimmed, the weight is distributed evenly across the surface. This prevents the “pivoting” or “wobbling” that can occur when using lower-quality, uneven shims.

This is the ultimate choice for complex systems or scenarios where existing slide-out hardware is sensitive to slight misalignments. It is overkill for a simple adjustment, but for high-end motorhomes with sensitive electronic leveling sensors, this is the only logical pick. It is an investment in the long-term health of the track drive system.

Do You Really Need Shims? Spotting the Signs

Shimming is not a first-step solution, but rather a corrective measure for specific mechanical issues. You know the slide needs attention when there is visible unevenness in the gap between the slide-out wall and the RV frame when the room is fully retracted. Furthermore, if the slide-out motor labors audibly or if the unit stops before a complete seal, it suggests the track is misaligned and fighting against its own friction.

Another common symptom is the “hesitation” during the extension process, often accompanied by a jerky, rhythmic motion. Before grabbing the shim kit, always check for debris in the track or worn rollers, as shimming cannot fix a broken mechanical component. If the hardware is intact but the geometry is off, that is the clear signal that a shim is required to restore proper travel.

How to Safely Install Slide-Out Track Shims

Safety begins with immobilizing the slide-out, as the last thing you want is for a heavy wall to move while you are working on the mechanism. Use mechanical braces or jacks to support the weight of the slide before loosening any track mounting bolts. Never rely on the motorized gears to hold the slide in place while your hands are in the work zone.

Once the load is safely supported, slightly loosen the mounting bolts—don’t remove them entirely if the slot permits sliding the shim in. Insert the stainless steel shim, ensuring it is seated flush against the structural backing to prevent shifting under vibration. Tighten the bolts in an “X” or “star” pattern to maintain even pressure and check for smooth operation before retracting the support jacks.

Choosing the Right Shim Thickness and Material

The rule of thumb for shimming is to use the thinnest material that corrects the alignment issue. Stacking too many thin shims can create a flexible, unstable sandwich that may eventually compress or slip out. Always aim for a single, solid-thickness shim if possible, as this maintains the structural integrity of the mounting connection.

Stainless steel is the mandatory material for this application because it is impervious to the rust and corrosion that typically plagues RV under-carriages. Avoid plastic, aluminum, or galvanized steel shims; plastic can crack under load, while non-stainless metals will eventually corrode in the presence of road salt or moisture. If you are unsure of the required thickness, start with a stack of feeler gauges to determine the exact gap before ordering the permanent shim.

Taking the time to properly align a slide-out track is one of the most effective ways to preserve the value and functionality of any mobile dwelling. By selecting high-quality stainless steel and following a careful, methodical installation process, you turn a frustrating mechanical headache into a non-issue. Keep your slide-out running smoothly, and it will keep the elements out for the long haul.