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https://www.researchgate.net/profile/Edwin-Odom/publication/2528341/figure/fig4/AS:652224900366344@1532513942192/Hand-drawn-sketch-of-the-coaster-brake-bicycle-hub-dissected-by-students.png

I tried to fix my coaster brake with no understanding of what I was doing. Suffice to say it's a long process.

I broke one of the ball bearing cages in disassembly, so I thought they were pointless fragile things and I threw them out. A bike can work on plain bearings, right?

From what I can tell, they were there to keep the hub from bouncing around on the axle. Now the chain won't stay on anymore. But I want a second or fifth opinion.

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    Can you post pictures? It's a bit hard to imagine what you mean by "I broke one of the ball bearings in disassembly". FWIW, coaster brakes are integrated into the rear hub. You likely reassembled the hub without parts of the bearings that support the entire wheel on the axle and allow it to spin properly around that axle. Dec 20, 2022 at 23:37
  • @AndrewHenle Right. I've added a link. Dec 21, 2022 at 13:01
  • "I thought they were pointless fragile things and I threw them out. " - in the future, save decisions like that for things you are an expert in, rather than subjects you have "no understanding" of. Dec 26, 2022 at 20:02
  • @whatsisname You're right, but in hindsight I like the idea of loose bearings and tacky grease. From what I can tell you can't buy caged bearings separately. It's really just as well. Dec 29, 2022 at 17:13

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What are ball bearings for in a coaster brake?

The bearings allow the hub to spin freely around the axle.
Cadged bearings decrease friction and make repair much easier than loose balls.

Your sketch looks something like this diagram
enter image description here

I broke one of the ball bearings in disassembly, so I thought they were pointless fragile things and I threw them out. A bike can work on plain bearings, right?

You broke one of the ball bearings during disassembly. This could mean that one of the individual balls was broken or that the retaining ring holding the ball bearings broke.

You threw out the broken bearings and then you say "A bike can work on plain bearings, right?"
This may mean that you put bearings in without the metal cage.
This is theoretically possible using loose bearings of the same size.

  • Coat the bearing surface you want to load bearings on with a tacky grease so the bearings will stick.
  • Fill the space where the cage lived with loose balls and then remove one so there is room for them to move.

Use the same size bearings as the ones that came out of the hub.

It might take some experimentation to get right.

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  • Seems easy. Where's a good place to buy these things? Dec 21, 2022 at 14:46
  • Plain bearing a type of bearing that has simply two smooth lubricated surfaces sliding against each other. Typically one of them is soft porous metal so that it can bed in and retain lubricant. And no, ball bearing races without bearings don't work that way.
    – ojs
    Dec 21, 2022 at 15:05
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    @EthanMiller bike spares are traditionally available from bike shops, though you will need some idea of the size you need, have you got any of the old ones remaining? Rear wheels I've seen have typically been 1/4 inch
    – Swifty
    Dec 21, 2022 at 21:39
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    @EthanMiller yes
    – Swifty
    Dec 22, 2022 at 17:25
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    @EthanMiller It would be best to measure the ball bearings you took out of the hub. They need to be the same size as what came out of the hub. Knowing the hub make and model might help locate documentation if you don't have the bearings to measure.
    – David D
    Dec 22, 2022 at 21:11

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