Radial Stiffness Test for ProX Carbon Rims

1. Purpose of Radial Stiffness Test

Stiffness is a critical performance parameter for carbon bicycle rims. Among the different stiffness characteristics, radial stiffness refers to the rim’s ability to resist deformation when a vertical load is applied. Higher radial stiffness allows the wheel to better maintain its shape under load, improving power transfer efficiency, structural stability, and overall riding performance. In general, rims with deeper profiles tend to provide higher radial stiffness due to their structural geometry. The radial stiffness test is conducted to evaluate how the rim behaves when subjected to a controlled vertical load. The objective is to confirm that the rim structure can withstand the applied force without cracking and that it returns to its original shape once the load is removed.

2. Test Procedure

The test is carried out by applying a vertical force to the rim using a calibrated loading system. Three test positions are selected on the rim:

• One position located at the valve hole area
• Two additional random positions along the rim circumference
• Applied Load: 40 kgf
• Test Frequency: 3 test cycles

At each position, the test machine applies a vertical load to the rim. The resulting deformation is recorded and analyzed. The loading cycle is repeated 3 times to ensure consistency of the results.

3. Test Standard

During the test, a specified load is applied vertically to the rim at selected positions around the rim circumference. The deformation of the rim under load is measured to evaluate stiffness performance. After the load is removed, the rim is checked to ensure that:

• nWhe a 40 kgf vertical load is applied, the rim must remain structurally intact
• No cracks or structural damage are allowed during the test
• After the load is removed and the force returns to 0 kgf, the rim must return to its original shape with no permanent deformation

4. Sample Rim Used for Testing

This rim represents a lightweight carbon road rim designed for high-performance cycling applications.

5. Test Results

The rim was tested at three different positions using a maximum applied load of approximately 40 kgf.

Maximum recorded deformation under load: 1.07 mm
Deformation after load removal (0 kgf): 0 mm

Conclusion: These results demonstrate that the rim possesses sufficient radial stiffness and elastic recovery characteristics, meeting the structural requirements for high-performance carbon rims.