FORM BIKE FITTING EXTRA STACKER KIT VT MTB 4/6MM
The FORM Bike Fitting Extra Stacker Kit V2 MTB (4/6mm) is a premium, glass-filled nylon add-on kit designed to extend the FORM V2 Walkable Leg Length Shim to provide 7mm to 10mm of total height correction.
The FORM Bike Fitting V2 Extra Height Stacker Kit is the definitive bio-mechanical solution for cyclists managing a moderate structural leg length discrepancy. When the standard 3–6mm height adjustment provided by the base leg length shim isn't quite enough to stabilize your pelvis, this highly specialized kit steps in. It completely replaces the standard 2mm stacker included with your base shim, providing an ultra-stable platform that eliminates pelvic rocking and chronic lower back or hip discomfort.
Crafted in the United Kingdom from rugged, high-strength glass-filled nylon, this kit is built to survive the high-torque, demanding environments of mountain biking and gravel racing. It features a 4mm extended stacker along with an optional 2mm clip-on spacer set, allowing you to fine-tune your exact height requirements. The engineered structure maintains a sloped, chamfered front profile to facilitate a smooth, unhindered foot entry into your 2-hole pedals.
Security and precision under load are guaranteed by an included extended steel cleat plate and high-tensile mounting hardware. Despite the increase in vertical height, this clever system preserves the core walkability of the original V2 shim architecture by aligning your cleat safely between the shoe's sole lugs. It provides professional-grade biomechanical alignment without relying on bulky, home-brewed foam hacks.
Key Features
Targeted Height Extension: Replaces the standard base hardware to increase your total vertical lift to a 7mm to 10mm range.
Tough Glass-Filled Nylon: Engineered from high-impact, industrial-grade polymer that resists compressing or cracking under heavy sprinting and climbing loads.
Maintains Core Walkability: Integrates seamlessly into the original V2 system geometry to keep your off-road walking stable while protecting your cleat.
Specifications
Material: CNC Machined and Molded Glass-Filled Nylon (Made in the UK)
Dimensions: 70 mm front-to-rear, 38 mm wide, 35 mm from cleat bolt holes rearward
Included Hardware: 4mm extended stacker, 2mm spacer set, cleat plate, shim screws, and extended cleat screws
Why This IS For You
✅ Corrects Pelvic Rocking: Perfect for riders with a moderate leg length variance who need extra lift to achieve equal leg extension at the bottom of the pedal stroke.
✅ Robust Component Integrity: Ideal for heavy gravel or trail usage, as the interlocking parts and premium steel cleat plate prevent the assembly from twisting.
✅ Smooth Pedal Engagement: Excellent because the sloped front edge prevents the extra height from catching or binding on your mountain bike pedal body.
Why This May NOT Be For You
❌ Requires Base Shim V2: This kit cannot be used on its own; it is strictly an add-on and requires the separate purchase of the base FORM Walkable MTB Shim V2.
❌ Requires Flat Shoe Sole: Due to the physical size needed for stability at this height, it requires a clean, flat shoe sole interface without obstructive, raised rubber areas.
❌ Not Mixable with Other Kits: The 4/6mm kit is engineered to work as a standalone lift unit and cannot be combined or stacked with the larger 8/10mm kit.
BFC PRO TIP
Because this kit lifts your cleat up to 10mm off the shoe sole, the clearing tolerances between your shoe's rubber lugs and your pedal mechanism become tighter. Before rolling out for a big trail ride, test your clip-in and clip-out tension on a stationary trainer or while holding onto a wall. If your shoe's natural rubber lugs are contacting the pedal body and making clipping out tight or sticky, you can use a sharp craft knife to carefully shave 1-2mm off the rubber lugs immediately surrounding the shim for a safe, crisp release every time!
