Optimal Mountain Bike Rim Design

Felt Bicycles, Irvine, CA

ID: CFO6

Relevant Skills: mechanical design, strength of materials, finite element analysis, composites

More and more manufacturers are making mountain bike rims out of carbon fiber to decrease weight and increase stiffness and strength. Lots of designs are coming out, and we've been observing the trends and trying to figure out what rim shapes will perform best. We'd like to get help from a design team to optimize the shape of a rim for mountain bikes. What I would propose is that we will supply the basic dimensions and shape for the tire bed, and the team will design the shape for the sidewalls and outer wall (part that interfaces with the spokes).

Lateral stiffness-to-weight will be the primary metric, but we're interested in the lateral stiffness of the wheel as a whole. Therefore the analysis could include FEA of the rim shape, plus simpler calculations to involve the hub and spokes.

The shape does not need to be symmetric, and because it will be molded in composites (rather than extruded like metal rims), it does not need to be a constant cross section. There is also the possiblity of getting the design into the layup schedule for prototype construction to add another dimension to the project.

Felt doesn't have any immediate plans to produce a MTB rim, but we work with a factory that is starting to work on their own designs. If we feel that the team has come up with a viable design, we may give the design to this factory to produce as their "open mold" (meaning that any company could buy it from the factory and brand it as their own, including Felt).