Carbon fiber rims are manufactured by layering sheets of carbon fiber pre-preg (pre-impregnated with resin) into a mold, then curing under heat and pressure in an autoclave. The layup schedule — the specific arrangement of fiber orientations and thicknesses — determines the rim's strength, stiffness, weight, and impact resistance.
Why Carbon?
Compared to aluminum, carbon rims offer a superior stiffness-to-weight ratio. A typical carbon mountain bike rim weighs 380-450g versus 500-600g for a comparable aluminum rim, while providing better vibration damping and allowing more aerodynamic profiles.
Key Specifications
Internal Width: The distance between the inner bead hooks. This determines which tire widths are compatible. Wider internal widths provide better tire support and a more rounded tire profile.
ERD (Effective Rim Diameter): Critical for spoke length calculation. Always verify ERD when ordering spokes.
Depth: Measured from the bead seat to the outer edge. Deeper rims are more aerodynamic but heavier and more affected by crosswinds.