How to Measure
Your Gearbox
A project intake checklist for identifying the unit and the dimensional information needed for a sourcing discussion.
IDENTIFICATION CHECKLIST · MODEL-SPECIFIC INSTRUCTIONS REQUIRED
Start with the exact unit.
Record the manufacturer, model, revision and installation location. “Gearbox” should identify the actual assembly; a derailleur, bottom bracket or other drivetrain part needs a different drawing and measurement reference.
Identify the part
Photograph the complete assembly and any readable model markings. State which component is being sourced or replaced.
Collect the manufacturer drawing
Use the model-specific drawing to identify the required reference points and measurement method. Do not infer a fit from overall appearance.
Record the mating interfaces
Supply the available mounting, shaft and clearance information from the approved drawing. Record units and the instrument used for any measurements you provide.
Separate measured and specified values
Mark which values come from a drawing and which were measured on a sample. Leave unknown dimensions clearly identified.
No universal measurement dimensions or tolerances are provided here. A model-specific method is needed before measurements can support a fit decision.
Prepare a measurement request ↗