What Bottom Bracket Do I Have? Identification Guide

A correct replacement has to match two independent requirements: the frame’s bottom-bracket shell and the crankset’s spindle. Identifying the part already installed adds a third record. Parts that look alike can require different adapters, spacers, tools and procedures, so appearance alone is not enough.

Short answer #

Find the exact frame and crankset model before ordering or dismantling anything. Confirm the shell specification in current frame documentation, confirm the crankset requirement in its compatibility documentation, then choose a bottom bracket whose exact part number is documented for both. Include every specified adapter, spacer, sleeve, seal and preload part in that check.

Record what is on the bike #

• Bike and frame. Record the brand, exact model, model year or generation, size and version. Add the frame SKU or serial number when the manufacturer uses it to distinguish specifications.
• Crankset. Record the brand, complete model code, variant and every visible identifier. Do not infer the spindle requirement from the brand or product family alone.
• Installed assembly. Photograph the drive side and non-drive side. Record all markings on cups, bearings, covers, adapters and spacers without changing their order.
• Mid-drive e-bike. Record the drive-unit manufacturer and exact model. Its service documentation may define the bearing and crank interfaces instead of a conventional bottom bracket.

Treat the existing part and spacer arrangement as evidence of what is installed, not proof that the current configuration is correct or original.

Identification workflow #

1. Start with the frame documentation. Find the service manual or technical specification for the exact frame, year or generation and version. Record the shell interface and its specification. A complete-bike listing describes factory equipment only; components on a used or customised bike may have changed.
2. Identify the exact crankset. Look up the complete model code and every variant identifier requested by the crank manufacturer. Similar cranksets can have different fitment and spacer requirements.
3. Use appearance only as a clue. Exterior tool fittings can belong to a bottom bracket threaded into the frame or to a thread-together unit installed in a threadless press-fit shell. A conventional press-fit unit normally has no exterior tool fittings, but the shell’s smooth, threadless bore cannot be confirmed through installed cups. These clues narrow a likely family; they do not identify the exact standard.
4. Route unusual systems to their exact manual. A one-piece crank, manufacturer-specific bearing arrangement, legacy system or mid-drive unit may not follow the usual threaded, press-fit or thread-together pattern. Keep it classified as unknown until the exact documentation confirms it.
5. Confirm the crankset requirement. Use current compatibility information for the exact crankset. Record the supported bottom-bracket family and every required adapter, spacer, sleeve, seal or preload component.
6. Cross-check one complete configuration. The frame manufacturer’s shell specification, the crankset manufacturer’s requirement and the replacement bottom-bracket manufacturer’s chart must agree. Confirm the exact replacement part number and full component arrangement; do not use a retailer listing as final compatibility evidence.
7. Select tools and procedures last. Identify the installed part’s removal tool and the replacement part’s installation tool separately. Take torque, thread direction, preparation compound, spacer placement and part-reuse instructions only from the current manuals for those exact parts.

What a photo or one measurement cannot confirm #

A photo, cup shape or single measurement may reduce the possibilities, but it does not independently establish:

• the exact frame-shell standard;
• the crankset and spindle requirement;
• the adapter, spacer and preload configuration;
• the replacement bottom-bracket part number;
• the required removal and installation tools.

Some systems cannot be distinguished without crank removal. If that is necessary, follow the exact crankset removal procedure; do not improvise a puller or removal method.

Check before ordering #

Order only when current manufacturer documentation confirms all of the following together:

• the exact frame, year or generation, version and shell specification;
• the exact crankset model, variant and supported bottom-bracket configuration;
• the exact replacement bottom-bracket part number;
• the complete adapter, spacer, sleeve, seal and preload arrangement;
• the correct installation manual and tools for that part.

Stop and get help #

Do not remove the bottom bracket, use a puller or press, or order a replacement when documents are missing or conflict, markings are unreadable, a conversion or adapter may be present, or the shell has loose cups, damaged threads, corrosion, distortion or cracks. If crank removal is required but the exact crank or procedure is unknown, ask the frame or component manufacturer or have a qualified bicycle mechanic identify the complete combination.

Common questions #

Can you identify a bottom bracket from a photo? #

A photo can sometimes narrow it to a likely family, but it cannot confirm an exact replacement. Adapters and thread-together units can hide the frame’s real interface.

Are all press-fit bottom brackets interchangeable? #

No. Press-fit describes an installation method, not one universal standard. The frame-shell specification and exact crankset requirement still have to match the replacement part’s current compatibility chart.

Can I use an adapter? #

Only use an adapter or conversion bottom bracket when the relevant manufacturers explicitly support the complete frame, adapter and crankset combination and publish a current installation procedure. Physical fit alone is not compatibility evidence.

Let Drais remember it for you #

Open your bike in Garage, go to Parts → Add part and select Bottom bracket. Save the confirmed brand and model, then record the frame-shell and crankset details in Photo & notes. Drais keeps this record with the bike, ready for the next service or replacement.