Diagnosing and Fixing Premature Bottom Bracket Wear in PressFit BB

Cyclists know how frustrating it can be to experience premature wear in crucial components such as the bottom bracket.

In this blog post, we will delve into a detailed transcript of the video that highlights the process of diagnosing and fixing a customer's complaint regarding premature wear on a BMC bottom bracket.

We will explore the inspection techniques used, measurements taken, and the ultimate solution employed to address the issue.

Diagnosing the Problem:  The technician's first step is a visual inspection, looking for any visible damage or obvious issues. This is followed by a tactile inspection, running a finger over the surface to detect irregularities.

Measurements and Clues: After detecting an abnormality during the tactile inspection, the technician proceeds to take measurements using a bore micrometer. By carefully moving the micrometer around the bottom bracket, they notice that the dimensions change slightly, indicating an underlying problem. To gather more precise measurements, an internal micrometer is used on both the non-drive and drive sides, revealing a significant difference in dimensions.

Identifying the Solution: With the measurements suggesting misalignment and unevenness in the bottom bracket, the technician suggests a solution. First, they focus on addressing the tightness on the non-drive side, using a specialized tool called a 40.98 Reamer to carefully remove a tiny amount of material and achieve perfect roundness and size. Once the non-drive side is corrected, the technician plans to revisit the drive side and address any remaining misalignment by light sanding.

Executing the Solution: The technician demonstrates the use of the 40.98 reamer tool, ensuring that the correct amount of pressure is applied to shave off microns of material. They emphasize the importance of keeping the tool and the bottom bracket wet to control carbon dust and maintain smooth operation. The process involves a patient and cautious approach, taking time to avoid any issues that could affect the overall integrity of the bottom bracket.

Conclusion: The video provides valuable insight into the diagnosis and resolution of premature bottom bracket wear. It highlights the importance of thorough inspections, accurate measurements, and the use of specialized tools to address the issue effectively.