Bike Brake Caliper

February 2026 - June 2026 | MECH_ENG 240: Intro to Mechanical Design and Manufacturing

A set of 3D printed caliper arms for the rear brake of a road bicycle. Used CAD, FEA, and topology optimization (NX) to create and refine the design.

Needs and Constraints

To begin the project, we created a functional decomposition diagram to establish the needs our design would need to address. We then used this to define 19 different quantifiable metrics by which to judge the success of the design. The acceptable and marginal ranges for each metric were sourced from ISO standards, benchmarking analysis, scientific papers, and hand calculations.

We also defined the physical design space of the project. The caliper arms need to interact properly with the bike's rim and brake cable, and fit with specific mounting points.

Topology Optimization

By inputting the expected loads, mounting points, and design space into the topology optimization tools within Siemens NX, we are able to generate the stiffest possible designs while reducing mass - two metrics established earlier in the design process. We used these results to inform the geometry of our initial designs. For example, both the left and right caliper arms show I-beam or C-beam geometry, which we incorporated into both final models.

Left caliper arm top op results

Right caliper arm top op results

FEA

After each revision to the caliper CAD, we ran FEA on each arm individually, and plotted the nodal stress and deformation. The nodal stress plots gave us confidence that the arms would not fracture or snap during use. The deformation plots allowed us to compare stiffness to performance. We found that our first iteration was actually too stiff, requiring too much grip force on the brake lever and locking the brakes too quickly, so our next design aimed to increase deformation.

Nodal stress plot of final right caliper design

Deformation plot of final right caliper design

Results

The final design performed very well in weight reduction, deflection, brake feel, and ease of assembly. However, the design still took a greater amount of brake lever force than defined as acceptable by our metrics table. We found that there was a significant tradeoff between stopping distance and brake lever force. Brake calipers that were stiff enough to stop the bike within the distance defined by ISO standards required a large amount of grip force on the brake lever. Brake calipers that took an acceptable amount of force to lock did not stop the bike quickly enough. Ultimately, we decided that complying with ISO regulations and braking quickly was more valuable to the performance of the calipers than the required lever force. In the future, increasing the mechanical advantage of the brake system by moving the pivot points and arm lengths could help to resolve this issue.

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