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Fitted brand new 'Enduro' branded bearings to my Fulcrum rear hub last week. Two in the hub and two in the freehub. First ride last Wednesday and all is well, second ride yesterday still ok. I took the bike out this lunchtime and while riding at a steady pace along a stretch of road to get to my local trains I hear a god-awful noise coming from the hub. I stop to check it and it doesn't sound good so I take off the rear axle and freehub together and to my suspicion it seems like the near-side freehub bearing has gone a bit wonky. Can't check it because I can't remove the cassette so I head off home.
I get home, take off the cassette and freehub and tiny ballbearings drop everywhere. The near-side bearing, 3 rides in, has disintegrated.
I installed the bearings with a proper bearing press so my guess is that this is just a rogue bearing that shouldn't have made it through quality control, but I thought I'd better check with the Singletrack collective mind to see if its something I've done wrong before getting on to the vendor.
Pretty unusual, check you haven't missed out a spacer from between the bearings which would then allow them to be forced out of alignment, and break in a similar fashion to the way yours have.
All spacers are there I think. Here's an exploded (no pun intended) diagram of the freehub assembly;
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Its the bearing circled in red that disintegrated. What this diagram doesn't show you is that this particular bearing is held in by a circlip which goes just before the metal spacer circled in green. If the bearing isn't seated properly then the circlip won't click in place.
I've re-greased and popped one of the old bearings back in to keep me going until I can order a new one.