🚴‍♂️ Bottom Bracket Compatibility Cheat Sheet — Know What Fits What

Understanding your bike’s bottom bracket (BB) helps you choose the right crankset, axle (spindle), and bearing setup. Here’s a quick reference you can use before upgrading parts or buying upgrades:

🔧 What Is a Bottom Bracket (BB)?

It’s the part of your frame where the crank spindle and bearings live. It connects the crankset to the frame and allows smooth pedaling rotation.

📋 Common Bottom Bracket Standards

🔩 Threaded (BSA / English)

• Shell width: 68 mm / 73 mm

• Spindle compatibility: 24 mm, 30 mm & DUB with correct cups

• Great all-around choice, easy to service, widely supported.

🛠 Press-Fit BB86 / BB92

• Inner diameter: ~41 mm

• Designed mainly for 24 mm spindles

• Press-fit bearings in cups, common on road & MTB frames.

🔩 BB30

• Inner diameter: ~42 mm

• Cranks with 30 mm spindles press directly into the frame

• Very stiff & efficient but needs precise fit.

🧱 PF30

• Larger ID: ~46 mm

• Can fit 30 mm spindles and often adapted for other sizes with inserts

• Designed to combine stiffness and easier bearing fit.

🔩 BB90 / BB95

• Press-fit standards originally from Trek

• Designed for 24 mm spindles only — no 30 mm option.

🧰 T47 Threaded Press-Fit

• Threaded standard with larger ID (~47 mm)

• Supports 24 mm, 30 mm & others with proper cups

• Easier mechanical service than pure press-fit systems.

🧠 Quick Compatibility Rules

🔹 24 mm spindles (Shimano Hollowtech II) are common in BB86/92 and BB90/95 designs.
🔹 30 mm spindles (BB30/PF30 and adapters) offer higher stiffness and modern performance orientation.
🔹 Threaded (BSA or T47) is easiest to service at home and avoids many press-fit creaking issues.

📌 Quick Fit Checklist

1. Check your frame BB shell type:
   Threaded or Press-Fit?

2. Measure BB shell width & ID (e.g., 68 mm / 41 mm ID) to identify the standard.

3. Match spindle/crank diameter (24 mm or 30 mm) with a compatible BB or adapter.

🔧 Common Upgrades & Notes

✨ You can often adapt standards using adapter kits — e.g., running 24 mm spindles in a BB30 with adapters — but it’s best to match the crank and BB as cleanly as possible for stiffness & longevity.

🚩 Why It Matters

Choosing the right BB + crank/spindle combo ensures:
✔ Smooth pedaling feel
✔ Proper chainline & drivetrain efficiency
✔ Reduced noise and wear
✔ Easier service & longer life

📩 Unsure what bottom bracket your bike has? Snap a pic of the BB shell (measure width & internal diameter) and send it to us — we’ll help you confirm compatibility!

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