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I have been given a bike for free, as the rear wheel was very wobbly.

I'm been learning how to take things apart, and investigated the axle - it's not bent.

The ball bearings, however, were a surprise. There were 9 on one side (the side of gears) and none on the other side. Those 9 balls were kind of loose (I think 10 could fit well), and there was a smashed up steel ring in there.

I'm not sure if that's something "useful" (eg, reduces friction?), or if it's the "dust cover" that got pushed in and smashed thinner. I found it weird that only that side lacked a steel dust cover.

Could you help me understand if this was just a bad maintenance job (the rear wheel is clearly newer than the front one) or if it makes sense to have ball bearings only on one side?

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  • At some point the axle was either taken apart or came loose and the balls on the other side were lost. – Daniel R Hicks Aug 18 at 19:37
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    Oh, and check to see if the missing balls are actually stuck inside the hub. – Daniel R Hicks Aug 18 at 19:46
  • A photo of all the parts would help us provide a better answer, particularly what the ‘smashed ring’ is. – Argenti Apparatus Aug 18 at 20:37
  • "Those 9 balls were kind of loose (I think 10 could fit well)"  — this is expected. If you see that a bearing could take N balls, you should only install N-1 balls there to prevent them rubbing against each other. – Grigory Rechistov Aug 19 at 7:38
  • @ArgentiApparatus You are right, I will edit the post with a photo of the parts. – Fabio Aug 19 at 12:01
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There are supposed to be ball bearings on both sides of the hub. You need to rebuild the bearings replacing at least the non-drive side balls.

Bicycle hubs with loose ball bearings use a ‘cup and cone’ system. The cups and cones have the bearing surfaces and the balls are sandwiched between them. The cups are in the hub, the cones are threaded into the axle.

There are many videos on YouTube that will show you how to disassemble, repair and reassemble a cup and cone hub. RJ The Bike Guy has a good one.

You’ll need to inspect the cup and cone bearing surfaces for wear or pitting. the axle, cones, spacers and balls can all be replaced. Balls come in a couple of different sizes. If you don’t have accurate calipers a local bike shop can help you out.

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    The most commonly seen details of a bicycle rear hub is the cup and cone with loose ball bearings numbering 9 per side. The balls measure 1/4" in diameter. – Jeff Aug 19 at 2:49
  • I've attached the only picture I have right now, can do others if needed. The dust cap can be seen dangling on the axle. The steel ring is black with old grease, near the balls. – Fabio Aug 19 at 12:07

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