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Replacing fork on bike but messed up and didn't keep all the pieces in order as I took the old fork off. Which direction do the caged bearings go? What side of bearings face the cup and which side to the cone? Thanks

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    Look at where the two races are - they will be at an angle. if you put the bearings in and the bearing balls aren't aimed at the race, then its upside down, flip it and recheck.
    – Criggie
    Nov 1, 2022 at 3:22
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    youtu.be/61Gygv82DAM Nov 1, 2022 at 3:22
  • @DanielRHicks if you can summarize that video, it seems like a reasonable answer.
    – Weiwen Ng
    Dec 1, 2022 at 20:26
  • DanielRHicks that was a very helpful video! Thank you
    – Alison
    Feb 24, 2023 at 5:37

3 Answers 3

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When replacing your headset bearings you must have the non caged side ( the balls ) facing into the cup that sits on your frame , this means that when the headset is compressed together the ball bearings can roll on the cup allowing the handlebars to turn.

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There are variations depending on the design.

Here is a picture with two common configurations.
enter image description here

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bearings; sealed and loose

The key to orienting caged (loose) bearings correctly is to observe that the races do not work together in pairs, but in quadruples.

If it were just a pair (sealed bearings; top left of the figure), the load of the rider (red arrow) would be supported at the axle (black arrow) vertically.

Just one bearing (top left) would in theory be enough. You still need a pair of sealed bearings (top left and right) to avoid sway.

The load applied in loose bearings (two red arrows; bottom of the figure) arises from a combination of the rider weight as well as the clamping force. The two forces are counter-acted by the axle (two black arrows; bottom of the figure). (Hence, incidentally, the axle holds compression forces.)

Comparing the two figures also clarifies why the clamping force matters so much with loose bearings. It can be neither so high to lock the bearings, nor so low for them to be loose. It has to be "just right".

Here I used the term "vertically" on the assumption these are hub bearings, but the same idea applies for the headset if you look at it sideways. The same also applies for the bottom bracket, except that the load will alternate between left and right.

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    Slight clarification: the diagrams do not depict sealed vs loose bearings, but rather radial contact vs angular contact ones.
    – MaplePanda
    Nov 1, 2022 at 22:53
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    Well, but which way do the caged bearings go then? That was the question. Which side to the cone and which side to the cup? Nov 2, 2022 at 15:38
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    "Here one simply needs to make sure the cage will not rub on either of the two races." While that does nicely follow from the video linked by Daniel in the comments, I do not see how that in any way follows from this answer, which mostly presents the theory of load bearing by ball bearings. Nov 2, 2022 at 17:57
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    Or I see but it is very well hidden and very hard to see. At least for me. One has to understand that the while the two rop cuts cannot be the same bearing cut at two locations (the orientation is wrong), it is how one should interpret the bottom figure. Perhaps. Maybe not. The text in the answer is really hard to understand und will not help a clueless person too much. Nov 2, 2022 at 18:03
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    I am also not quite seeing how this answers the question? Also, the top figure appears to be a cross section of one bearing. The text describes each side as one bearing. This ... seems off? Bearings are toruses.
    – Weiwen Ng
    Dec 1, 2022 at 20:22

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