Can I fit a Hollowtech II crankset on a square-taper bottom bracket?
By Crankworthy · Published · Updated
No — not on that bottom bracket. A Hollowtech II crank carries its own 24mm spindle and needs an external-bearing bottom bracket, so the square-taper cartridge comes out. On a standard threaded (BSA) frame the new bottom bracket threads straight in.
Why
On a square-taper setup the spindle is part of the bottom bracket cartridge, and each crank arm is pressed onto a tapered square at the spindle's end.
On Hollowtech II the spindle is fixed to the drive-side crank arm. The bearings sit in cups outside the frame shell, and the spindle slides through them. The two systems share nothing at the bottom bracket.
The conversion is common and usually simple: remove the old crank and cartridge, thread in a Hollowtech II bottom bracket, fit the new crank.
How to tell what you have now
- Square taper
- Each crank arm is held by a single bolt in the centre of the arm, onto a square spindle end.
- Hollowtech II
- The non-drive arm clamps onto the spindle with two pinch bolts, and bearing cups are visible outside the frame.
Tools and a bottom bracket for the conversion
The first three remove the old crank and cartridge; the BBT-9 installs the new Hollowtech II cups.
- Park Tool HXS-1.2 Pro Hex Wrench SetL-shape hex wrench set 2-10mm, workshop grade$28.95Amazon
- Park Tool CWP-7C Universal Crank PullerExtracts square taper and splined (ISIS/Octalink) crankarms via internal M22 threads$17.95Amazon
- Park Tool BBT-22 Bottom Bracket Tool20-tooth splined tool for square taper / ISIS cartridge bottom brackets
- Park Tool BBT-9 Bottom Bracket ToolExternal BB cup tool for Shimano Hollowtech II / SRAM GXP / DUB (BSA)
- Shimano BB-MT501 (BSA)Threaded BSA 68/73mm external bearing BB, 24mm Hollowtech II, alloy cups
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