The rear axel is a Kung Ten W5ER from a 1999 Trek 4000. The freehub was sticking so I was taking the axle apart to free up / clean / lube the freehub.

I noticed after it was apart that there are 2 sizes of ball bearings for the axle, and I don't know which side gets the bigger bearings.

I know I'm in trouble, any ideas out there?

  • If you want to be sure, assemble it with half the small balls on each side. The side that has most play is where the larger balls should go. Of course, next time, you'll lay the parts out carefully in the order that you remove them!
    – andy256
    Commented May 2, 2015 at 7:18
  • Generally, if the balls are smaller the corresponding races will be smaller. Commented Aug 23, 2017 at 20:51

2 Answers 2


Most hubs are same size both sides (9 quarter inch bearings). If they aren't, normally its the smaller ones on the freehub side (slightly smaller than the other side, maybe by a 32nd of an inch) and the larger ones are like a quarter inch and on the opposite side.


Almost 6 years late. The cassette side has 10. I just took mine apart and was really surprised when the 10th one came out. I did have the foresight to put them in separate bowls.

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