I lost a ball bearing today. Is it okay to go to a hardware store and pick up a general 1/4 in. steel plain ball bearing to replace it? Performance is not a concern, only longevity of parts.

  • The most important thing is that the replacement ball be exactly the same size as the one it replaces. There are several different standards for how balls are sized, and you wouldn't want to, eg, get a metric one to replace an imperial one. Apr 17, 2021 at 21:49

1 Answer 1


Ideally, no. Bearing balls are of such fine tolerance that a random substitution is likely to be bigger or smaller than your existing ones.

The best solution is to buy a set, then replace all the bearings on both sides of the axle. That way they've come from the same batch and will be all the same size. You can get bearing ball sets from your local bike shop or just buy 20 of the above.

A proper bike shop won't even reuse a new bearing that has dropped on the floor by accident, they'd just get another from the same batch.

Why is size such an issue? Imagine if your single replacement was slightly larger. The two balls either side of the new one would not take as much load, and may be free floating due to the bigger new ball taking extra load.

This leads to extra pressure on one ball and premature wear and failure, and at least two balls simply sliding around and not rolling. This generates wear because of a lack of preload on those balls.

Upshot is Spalling where the big ball looses chunks, which adhere to the race, and then peel off leaving dents. When this happens, your cones need replacing and/or the hub is dead.

If the new ball is too small, the same thing happens but the new ball simply slides and the two on either side take more load.

In short, a set of new bearings is cheap, just do it. You can get loose balls or you can get balls in a cage which are more convenient, either is fine.

On the flip side, I have sometimes used a spare bearing ball to repair an old donor bike at a fixup. A kids bike that might only do a hundred miles travel in its entire life would probably be fine for this fix, compared to a race bike doing a hundred miles a ride, or a long-distance commuter who does a hundred miles a week.

A bearing ball in a bicycle is not a high-load nor a high-speed application, so physically the bearing ball would function at the RPM and temperatures of a bicycle hub. The size and tolerance is the main issue.

So it's up to you and the expected longevity you expect from that wheel.

  • 1
    Is this only about loose ball bearings? Aren't the general-purpose ones more likely to be industrial units (sealed or not)? Apr 19, 2021 at 13:36
  • @VladimirF yes this question is about loose (or caged) bearings. A bearing cartridge would not fit OPs bike, and would not have lost a single ball in the first place.
    – Criggie
    Apr 19, 2021 at 19:33
  • I do not see where the OP speaks about a single ball. Apr 19, 2021 at 19:35
  • @VladimirF "I lost a ball bearing today. " and the link in the original question was to a single bearing ball costing 85 US Cents.
    – Criggie
    Apr 19, 2021 at 19:36
  • 1
    I am not a native English speaker but I see a difference between loosing a ball bearing and a single bearing ball. I did not inspect the edit history, though. Apr 19, 2021 at 19:37

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