Does anybody know what lower headset bearing I need for a 2012 Giant Trance X2? It’s an overdrive (not overdrive 2) headset. I can’t see any markings on the bearing, but it looks to be 40mm ID 52mm OD around 8mm thick with a bevel.

http://www.canecreek.com/headset-fit-finder

Thanks. I was hoping just to replace the bearing though. The cups feel fine.

A bit more digging suggests that the headset is the same as the overdrive 2. There is just a reducer in the top bearing to reduce it from 1 1/2 to 1 1/8. The bottom bearing is 1 1/2 in both and that’s the one that I can’t find.

In case anybody else comes looking for an answer to the same question, I ended up ordering one of these and it seems to fit just fine:

http://superstar.tibolts.co.uk/product_info.php?products_id=439

It seems that basically all you need is a 45×45 ACB with 40mm ID, 52mm OD and a depth of 7mm.

The 45×45 refers to the fact that there is a 45 degre bevel on both the inner and outer races. ACB means angular contact bearing and the other numbers are just the inner (ID) and outer (OD) dimensions.

Hope make a replacement bearing that looks as though it might fit and may be better quality than the Superstar one, but I didn’t try it:

http://www.wiggle.co.uk/hope-15-tapered-headset-cartridge-bearing/