A bike rim is a fundamental component of a bicycle wheel, forming the outer edge onto which the tire is mounted.
Construction and Materials
The rim is the circular structure that connects to the wheel's hub via spokes (or sometimes directly). Its construction and the materials used have evolved over time:
- Common Construction: The reference states the rim is commonly a metal extrusion that is butted into itself to form a hoop. This metal is typically aluminum alloy due to its balance of strength, weight, and cost.
- Modern Materials: Modern rims may also be a structure of carbon fiber composite, favored for its light weight and stiffness, particularly in performance cycling.
- Historical Materials: Historically, rims was historically made of wood, a material still found on some traditional or specialty bicycles.
- Combined Structures: Some contemporary wheels feature specialized rim designs where an aerodynamic carbon hoop is bonded to an aluminum rim on which to mount conventional bicycle tires, combining properties of both materials.
Common Rim Materials
- Aluminum Alloy: Durable, affordable, widely used.
- Carbon Fiber Composite: Lightweight, stiff, high performance.
- Wood: Traditional, often found on older or custom bikes.
- Hybrid (Carbon/Aluminum): Used for specific performance or aero benefits.
Function
The primary function of the rim is to provide a stable platform for the tire to seat onto, creating the airtight seal necessary for inflatable tires and providing a braking surface for rim brakes (though disc brakes attach to the hub). It also plays a crucial role in the structural integrity of the wheel, transferring loads from the rider and the road through the spokes to the hub.
