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Headset Bearings

It’s that time of year that we get asked about headset bearings…

All Bird bikes use ZS44 / ZS56 headsets. What does this mean?  Well, the diameter of the inside of our headtubes is 44mm at the top, and 56mm at the bottom.  The ZS part stands for “Zero Stack”.  So that’s the headset size sorted.

“But what bearings do I need?”  I hear you ask!  Well, here’s where it gets slightly more complicated

Most of our bikes ship out with our Bird headset, which happens to use the same bearings as a Hope headset.  The sizes are below, and can be bought through our website.

  • ZS44 36×45 degree 30.2mm ID 41mm OD
  • ZS56 45×45 degree 40mm ID 52mm OD

Before 2019 most of our complete bikes shipped with Cane Creek 40 headsets, which use 41mm top bearings (for the 1 1/8″ steerer tube) and 52mm lower bearings (for the 1.5″ tapered steerer tube).


Standard bearings from the Cane Creek 40 are steel, whereas the Cane Creek 110 headset uses stainless steel bearings which are compatible.

Just to be absolutely clear, here are the Cane creek part numbers, type and RRP of replacement headset bearings for your Bird Bike:

Stock Code Outer Diameter Series RRP
CBAA0006K 52mm (1.5″) 40 (Steel) £12.99
CBAA0006S 52mm (1.5″) 110 (Stainless) £32.99
CHSS2030 41mm (1″1/8) 40 (Steel) £14.99
CHSS2031 41mm (1″1/8) 110 (Stainless) £39.99

You can buy replacement bearings here:

Cane Creek 40 Headset Bearings – Standard