Bicycles & e-scooters
How to choose suitable bicycle pedal spacers and cleat shims to fine-tune knee alignment and reduce discomfort during long-distance riding.
Long-distance riders seeking knee comfort should consider pedal spacers and cleat shims as a precise way to optimize knee alignment, pedal stroke, and overall ride efficiency without compromising power.
Published by
Charles Scott
July 23, 2025 - 3 min Read
When you embark on long rides, small changes in how your foot sits on the pedal can ripple through your entire kinetic chain. Pedal spacers and cleat shims provide a practical method to adjust float, inclination, and lateral position, helping you align your knee with your upper leg during each pedal stroke. The goal is to reduce knee torque that travels through the joint with every push and pull, especially when fatigue sets in. Start by assessing your current fit: observe whether your kneecap tracks straight ahead, whether there is any warmth or discomfort behind the knee, and whether your hips feel evenly loaded. Small adjustments can yield meaningful relief.
Before choosing spacers or shims, know that two key factors influence knee comfort: cleat location relative to the ball of the foot and the angle of the pedal axle. Spacers alter the height between the shoe and pedal, subtly changing the knee bend. Cleat shims adjust rotational alignment, which can influence how your foot pedals through the 3 o’clock to 5 o’clock range. By understanding how each adjustment shifts knee biomechanics, you can create a stable foundation for hours on the road. It’s wise to measure your current stack height and track any changes in your subjective comfort scores as you experiment.
Incremental testing is essential for sustainable comfort gains
The first step in a careful selection is identifying your baseline pedal stack height and cleat setup. If your knee tends to cave inward or your shin shows signs of strain after a long climb, spacers may help by increasing the effective crank length and reducing excessive knee valgus. Conversely, if you feel clunky or delayed on the upstroke, you may need a minimal shim to adjust rotation so your foot lands more directly under the hip. Remember, the spacers influence distance from the pedal axle, while shims adjust rotation. Keep your changes incremental and monitor how your knees respond after 20–30 minutes of riding.
When selecting cleat shims, the principal aim is to correct relative rotation between the foot and leg. A small medial or lateral shim can correct a tendency for the knee to track outward or inward, which often causes discomfort in the outside or inside of the knee. If you notice toeing-out during the pedal stroke, a lateral shim can correct this drift. If your knee nearly rubs the frame or you hear squeaks from the cleat area, step back and recheck your alignment. It’s important to avoid overcorrection—tiny adjustments usually deliver the most stable, sustainable results on long days.
Fine-tuning should respect your entire kinetic chain and comfort
The practical approach to spacers begins with deciding whether you need a higher or lower stance to reduce knee bending strain. A higher platform can slightly straighten the leg during the bottom of the stroke, reducing pressure on the patellar tendon for some riders. A lower stance, conversely, can improve knee flexion range for those with tighter hips. In both cases, pair the spacer with a compatible cleat shimming plan so you don’t create an inconsistent footprint. Record ride duration, perceived effort, and pain location after each change, then compare notes across multiple rides to avoid chasing a momentary sensation.
Another critical factor is pedal type and crank length. Heavier riders or those with longer femurs often require more nuanced shim compositions to avoid knee torsion during high-power efforts. If you use a road-specific cleat position, reinvestigate your stance width and toe-in ratio, as these components interact with spacers and shims. Consider consulting a professional bike fitter for a precise three-dimensional alignment. The fitter can also check hip flexibility and ankle range of motion, ensuring that changes to foot position harmonize with your entire kinetic chain, not just the knee area.
Stepwise testing and documentation support durable gains
Knee discomfort on long rides frequently signals a mismatch between lower-leg alignment and pedal plane. Pedal spacers that lift the shoe a fraction can encourage a more neutral tibial angle, which reduces lateral knee stress in some cyclists. However, a spacer that’s too thick may cause overextension or alter your balance in a way that compromises efficiency. The key is to maintain a natural knee tracking path while preserving stable ankle articulation. Always recheck cleat engagement after altering spacers, since a change in vertical height can shift how your foot distributes pressure across the footbed.
Consider the sequence of adjustments as a managed experiment. Start with a minimal spacer change, ride for a set distance, then add a very small cleat shim if needed. Use a consistent riding route or trainer session to compare sensations. Note differences in knee soreness, shin stiffness, or hip fatigue. If the knee feels more symmetrical and reports less ache after a modest increase in spacer height, you likely found a beneficial balance. Keep the process natural and avoid forcing broad changes on the knee with excessive shims.
A methodical approach builds reliable, lasting comfort
Long-distance riders often confront asymmetries that complicate knee tracking. Spacers and cleat shims offer a practical means to address those asymmetries without buying a completely new pedal system. Start by documenting your baseline comfort levels: pain location, intensity on a 0–10 scale, and how stiffness evolves during the ride. Then apply a small spacer and subsequently a mild shim, waiting for a couple of rides to confirm trends. If discomfort recurs or shifts to a new area, revert to the previous setup and re-evaluate your foot position. Monitoring progress helps avoid over-corrections that destabilize your knee.
The interplay between shoe, spacer, and cleat is nuanced. Shoes with different stack heights can affect how a spacer impacts knee alignment, so always consider shoe model and insole thickness. If you rotate through several cycling shoes, you may need a different spacer-and-shim combination for each pair. In-depth testing should include mountain, gravel, and road settings if you ride diverse terrains. Consistency in measurement—torque felt, cadence, and reported comfort—will yield actionable data. A methodical approach turns trial-and-error into a reliable fit protocol.
When you’re ready to finalize your setup, aim for a configuration that preserves natural knee rotation and minimizes lateral knee pressure through the entire pedal stroke. Your chosen spacers should maintain sufficient foot stability, while shims should correct any undesirable toe-in or toe-out tendencies. If you notice new pressure points on the forefoot or heel, revisit your stack height and outer shoe width to ensure that the system remains harmonious with your foot anatomy. A stable pedal footprint helps transmit power efficiently without triggering fatigue in surrounding joints.
In the end, the goal is a lightweight, durable alignment that supports long miles without discomfort. Pedal spacers and cleat shims are tools to fine-tune knee mechanics, not quick fixes. Embrace a slow, measured testing plan, validate changes on multiple rides, and prioritize comfort over raw power gains. By aligning your knee with your hip and ankle through thoughtful spacer and shim choices, you can enjoy smoother pedal strokes, reduced fatigue, and better endurance. Regular reassessment keeps your setup responsive to changes in flexibility, terrain, and aging joints.
