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I recently noticed a strange "sand paper feeling and noise" when turning the wheel of my bike, and decided that it was time to learn to service the bearings of the hubs (cups and cones bearings, not sealed ones).

I discovered that the cone looks like this: worn bearing cup

The cup on the hand seems to be fine. cup

I have few questions related to this:

  • Is it normal wear, or can it be avoided by more systematic maintenance? - if the info is relevant to answer, it's the side with the brake rotor, the other side has a discolored mark, but is smooth.
  • What would be the cause, ingress of dust/sand in the bearings? (I'm riding between 200km and 400km per month, mix of road, gravel (dusty) and light forest trails, the bike is almost 2 years old), almost only dry. There was still a fair amount of grease in the bearing.
  • I couldn't find a matching parts on large online bike shops: is this part part of a wider standard and can I find only the cone, or I should I replace full bearing? (cone/cup/bearings). In the second case, what would be the "key measurements" to consider when looking for bearings? (I didn't find the info on Formula's website - the hub is a formula DC20/22 according to the spec sheet of the bike).
  • If finding parts is difficult, are there consequences of continuing to use the wheels/hub? (except accelerated wear?). Before this discovery, I was actually considering buying a second pair of wheels and keep the current ones for winter/spares.
  • [ADDED] I also noted clear bearing marks on the cone — I lock the suspension when riding on roads, would it be possible that a shock has cause such markings (not speaking about the fine marks that can be caused by sand)?
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    As an aside, you are riding quite a lot. You will generally have a lot of maintenance in fairly short intervals. Many occasional riders ride per year what you do in a month. Especially in dirty conditions I suppose you have to change your chain every 2 months, replace sprockets every few chain changes etc. If you are heavier than, say, 80 kg, you may experience frame breaks more than once in your life, etc.
    – Peter - Reinstate Monica
    Commented Sep 22, 2021 at 6:15
  • @Peter-ReinstateMonica Indeed, chains last 6 months (I clean/lubricate them regularly and have a gauge), and I'm at my third cassette (but the last change was not because of wear, but because of an upgrade). Servicing the bearings is not part of my routine, hence the question.
    – Rеnаud
    Commented Sep 22, 2021 at 7:41
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    If you mean with "bearing marks" that you can see indentations from single balls (as opposed to a more or less continuous groove) I think this can happen from tightening too much (at the moment of tightening) or, perhaps more commonly, from the bearing being too loose: Te load then rests only on a small number of balls and the resulting point pressure is enough to deform the cone surface. Especially with high dynamic loads (off-road, curbs).
    – Peter - Reinstate Monica
    Commented Sep 22, 2021 at 8:34
  • @Peter-ReinstateMonica I indeed meant indentations from single balls (4 consecutive balls in fact). Good to know that tightening can be a reason, I'll be extra careful when remounting.
    – Rеnаud
    Commented Sep 22, 2021 at 12:41

2 Answers 2

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  1. That is NOT normal wear and proper cleaning, lubrication, and adjustment would have prevented that damage.

  2. Riding in the rain, through puddles, washing the bike with water, or just dirt getting carried in by the air. From your description of your riding, there is plenty of dirt and grit to get in there. It just happens.

  3. Any LBS with a service department should have a supply of axle cones. The one you are showing is pretty common. You probably also need to replace the cup which is in the hub. The ball bearings are held between the cone and the cup. If one is damaged the other is almost always in similar condition.

  4. This will not run smoothly again and the wear will just accelerate. Eventually you will cause damage to non-replaceable parts if that has not happened already. Then you're looking at new wheels or at least new hubs.

UPDATE: You posted a photo of the cup and at least from what I see in the image, there does not appear to be damage there. So you need only to replace the cone. Check the bearings themselves and see if they need to be replaced also. They should be shiny and smooth with no pits or discoloration.

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  • Thanks for the reply and update. The bearings themselves are still shiny, and seem to be in very good condition.
    – Rеnаud
    Commented Sep 21, 2021 at 15:32
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    Bearings that ran on that cone are stuffed, they are so cheap they should be replaced regardless of how they look.
    – mattnz
    Commented Sep 21, 2021 at 22:00
  • @mattnz Isn't it a risk if I replace them with harder bearings to wear the cup, which would be much complicated to replace than the cone?
    – Rеnаud
    Commented Sep 22, 2021 at 12:37
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    Yes, the cup is harder to replace (if at all, often it means a new hub). The very best way to decrease wear on the cup is use new bearings from the same batch (avoiding size variations) with periodic servicing. In bicycles, the grease used does not matter much (Bikes bearings are not high pressure, high speed or hot and not expose to significant water).
    – mattnz
    Commented Sep 22, 2021 at 19:52
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If the bearing hasn't been contaminated, there's a good chance that this is a manufacturing defect or a cheap part that wasn't intended to survive in continuous use. Both would be good for warranty replacement if you notice them early enough.

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    Thanks, I added the picture of the cup, if it can help to provide "missing info" for this explanation.
    – Rеnаud
    Commented Sep 21, 2021 at 14:42

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