Spoke Hole Pull-Out Test for ProX Carbon Rims

1. Purpose of Spoke Hole Pull-Out Test

The spoke hole area is one of the most critical structural regions of a carbon rim. Each spoke nipple is seated at the spoke hole, where it transfers tension from the spoke to the rim structure. During wheel assembly and riding, these areas are subjected to significant tensile forces generated by spoke tension. To ensure durability and reliability, the spoke hole region typically requires additional carbon fiber reinforcement. If the structural design or material strength is insufficient, excessive spoke tension may lead to cracks around the spoke holes or spoke pull-through, which can compromise the entire rim structure. The Spoke Tension Test is conducted to verify that the rim can safely withstand high spoke tension without structural failure.

2. Test Procedure

The test evaluates the structural strength of the spoke hole area by applying a controlled tensile load through the spoke nipple. A 300 kgf tension force is applied to selected spoke holes using a calibrated tension testing device. A total of seven spoke holes are tested on the rim:

• One spoke hole located at the valve hole position
• Six additional spoke holes distributed around the rim

During testing, the load is gradually increased until it reaches 300 kgf, simulating the high spoke tension that may occur during wheel building or riding conditions.

The spoke hole area is carefully inspected while the load is applied to check for:

• Cracks in the carbon structure around the spoke hole
• Spoke nipple pull-through
• Structural deformation or damage

3. Test Standard

To pass the spoke tension test, the carbon rim must meet the following requirements:

• The spoke hole must withstand a 300 kgf tensile force
• No cracks are allowed around the spoke hole area
• No spoke pull-through is permitted
• The carbon structure must remain intact throughout the test

These criteria ensure that the rim can safely tolerate the spoke tensions typically used during wheel assembly.

4. Sample Rim Used for Testing

This rim represents an ultra light carbon rim designed for cross-country mountain bike applications.

5. Test Results

Seven spoke holes were tested under a maximum spoke tension of 300 kgf.

Conclusion: These results confirm that the rim provides sufficient reinforcement at the spoke hole area, ensuring reliable performance under high spoke tension during wheel building and riding conditions.