I'm looking to replace the bearings in the headset on a brand new GT mountain Bike (they have disintegrated after 4 weeks).They were the caged type but exposed so I can see each of the balls in the ring (i.e. not sealed)

I know from Cane Creek site that I have ZS 44/28.6 & ZS44/30 sized headset but no clue what the relationship is to my bearing size....sorry if this is a silly question!

Can anyone please recommend where I can buy the bearings?

  • 1
    The easiest way is to measure the size of a ball with a vernier caliper. A common size is 5/32''. Feb 26, 2017 at 12:22
  • 3
    If the bike is 4 weeks old from brand new, its under warranty. Take it back to the shop and request it be fixed under warranty.
    – Criggie
    Feb 26, 2017 at 18:28

1 Answer 1


Ball size is ideally measured either with a caliper or, more commonly in shops, with a purpose-made tool that has a hole for each size to compare against. 5/32" is the most common size for headset bearings by far, but 1/4" and 3/16" are also around. (So it's not a silly question, and it doesn't have any relationship to the headset size per se.) There aren't any oddball in-between ball bearing sizes used on bikes, so to get the size you're safe holding an individual bearing next to a ruler and eyeballing the 5/32" or 3.97mm.

It's likely to be the most common of them, 5/32x22 (22 balls). 5/32x20 also exists so it's wise to count or compare the old alongside the new. Both are common and super cheap bike shop items. 5/32x22


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