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After a while (e.g. 10 years or 40,000 km) the bearings in the hub of a wheel become worn-out -- this is with disk-brakes i.e. where the wheel's rim isn't worn-out.

The bike shop told me that it's not cost-effective to replace just the worn-out hub, because that would mean relacing the spokes -- instead they replace the whole wheel.

Is that sensible?

Is it possible to, instead, replace just the internal parts of the hub, reusing the exsising case (with its spokes etc.)?

I'd like to know for next time, please -- my new wheel and hub is "Shimano XT HB-M8000 Center Lock Disc front Hub".

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  • By case (of the hub), I think you mean the hub shell.
    – Weiwen Ng
    Jun 27, 2022 at 10:50
  • If you say so. I meant the bit to which the spokes are laced -- if I don't replace that then it's easy to keep the rest of the wheel -- and instead of changing that, only replace whatever is inside that (e.g. bearings), probably by removing new parts from a new hub.
    – ChrisW
    Jun 27, 2022 at 10:56

6 Answers 6

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Something may have been lost in translation, or some specifics not relayed in the post. The shop’s stance sounds odd in isolation. But it depends!

Assuming the hub had cartridge bearings, those are designed to be pushed out and new ones pressed in. Shops will have the tools to do both. Cartridge is a container with various contents: a bullet plus propellant plus primer in the military context, or printer ink (plus supporting electronics, these days), or film back in the good old days. In the cycling context, a cartridge bearing means that you get a unit that contains bearing balls plus the rolling surfaces that they run on (called the races), plus rubber seals. Cartridge bearings come in standardized sizes.

(NB: cartridge bottom brackets mean you get a sealed cartridge containing an older standard BB spindle plus the bearings that spindle turns on, which are usually cartridge bearings.)

In cycling, the alternative to cartridge bearings in hubs is cup and cone bearings. Here, the rolling surfaces are integrated into the hub and axle. When you take the hub apart, the bearings are loose. This is an older style. Typically, you want to open the hub up, clean out the old grease, and replace it periodically. If the loose bearings wear out, those are usually easy to replace and come in standard sizes. The cups and cones (the rolling surfaces) are harder to replace once they wear out, as they’re particular to the hub and don’t necessarily come in sizes standardized across the industry. I believe that for your new hub, the cones (attached to axle, those are the inner races for the bearing) are replaceable, but the cups are integrated into the hub construction and are not replaceable. Naturally, the availability of replacement parts down the line depends on Shimano’s continued existence, or sufficient demand for third parties to build replacement parts, but both are quite likely.

We don’t know what type of hub you had. Usually we don’t say that “the hub” as a whole unit is worn out. It would normally be the bearings in the hub that wore out. (NB: it’s possible that the flanges where the spokes attach failed, but this entails cracking from eventual metal fatigue, and we’d usually say cracked rather than worn out.) Now, the shop may be trying to convey that it isn’t cost effective to rebuild the hub, for whatever reason. Maybe it’s a cup and cone hub with worn cups. Maybe it was a cartridge bearing hub, but it was cheap enough that a built new wheel was more cost effective. We don’t know. In this case, it may have been possible to replace the hub internals, but it was just cheaper to buy a new wheel. For this particular hub model, it should be high quality, but it has to be emphasized that you do need periodic maintenance on this one. If you skip that, you’ll be revisiting this question eventually.

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    FYI, Shimano is an oddball - they still use cup and cone bearings i their wheels. So the bearing balls are easily replaced, but the cups are not.
    – Criggie ♦
    Jun 17, 2022 at 9:32
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    @Criggie That's the answer I think - if the cups are damaged, the hub shell is damaged, and that's one part with the flanges. Here's the exploded view (pdf). So it would mean rebuilding the wheel. If the cups are OK, fit a new axle kit, easy. Personally, if the cups are marginal, I'd buy a new hub, dismantle it to service the old one, and see how it rides, rebuilding the wheel if I don't like the feel - but I build my own wheels and tinkering with bikes is practically a hobby in its own right.
    – Chris H
    Jun 17, 2022 at 9:44
  • ... I suggest you (@Criggie) add an answer focussing on that, taking anything you like from my comment) - while this answer is right, the most useful bit is rather buried (I'm assuming the old hub is a similar Shimano, but other OEM-type brands use cup & cone - e.g. my tourer had Joytech hubs as stock)
    – Chris H
    Jun 17, 2022 at 9:44
  • it has to be emphasized that you do need periodic maintenance on this one I guess you mean re-greasing -- how often (or after how far)? I asked the guy at the store and he would only tell me that it will last a long time without maintenance. The Dealer's Manual seems to say only, "Apply grease to the indicated parts at periodic intervals."
    – ChrisW
    Jun 17, 2022 at 9:57
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    I'm not a pro mechanic, but having worked on a few Shimano hubs I can't see a failure mode that's ridable, but prevents a strip and regrease, possibly with new balls. I can see that he might not think it's worthwhile. If the hub's skipping that's likely to be a freehub issue. I'm familiar with those and the freehub can be replaced independently of the axle and bearings
    – Chris H
    Jun 17, 2022 at 10:27
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Yes, it is sensible. On the assumption this is an aluminium rim.

Wheels don’t just wear from rim braking. If this is a wheel used for off-road there will be accumulated fatigue in the rim at the spoke holes. Look close enough and you may find cracks in some of them. Dents and chips from the time you hit that rock/curb/goose will also exist.

Aluminium rims are not the majority cost of a wheel. Quality spokes and a quality hub make a significant portion of the cost and as you are not building the wheel yourself there is the shop time.

Consider a wheel to be a consumable part of a MTB. Your new wheel is great, it’ll last another 10 years or more if you don’t bend it.

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The Shimano XT HB-M8000 has a cup and cone bearing system. As such if the cups are damaged the hub is not able to be repaired (if the cones and bearings are damages these are easy and cost effective to replace). Presuming the shops advice is based on damages cups, which is entirely possible at 40k km, the shop is left with the options of offering a wheel rebuild with or without new spokes, or a new wheel.

This problem is often discussed on this site, with the answer universally being a new wheel is almost always more cost effective than paying someone to rebuild. The only situations where paying someone to rebuild is sensible is if an alternate wheel is unavailable (e.g. a vintage bike and originality is important), or the wheel is made up of particularly exotic (and expensive) parts worth keeping. A 10 year old production XT MTB wheel does not fit into this in any way.

Rebuilding the wheel with existing rim and spokes and a new hub requires a replacement hub with exactly the same flanges. The spokes have done 10 years and 40k km are at end of life, nipples could be ceased, and they could fail from the rework soon after the rebuild. This is a liability the shop would be carrying in terms of cost and reputation. A rebuild with new spokes is entirely possible, and a hand built wheel is usually better than a machine built, but you need to pay for spokes and time for the build as well as the new hub. The only thing being saved is the relatively low cost of the rim.

A new wheel is factory build with a machine, usually in a low wage cost country, by the hundreds at a time. These savings are significant and pass down the supply chain to the end price.

So yes, if the cups are stuffed, the shop is correct in advising a new wheel is the better option.

With a cup and cone bearing hub, regular clean and grease, with new bearings occasionally (very cheap), will usually prevent the cones being damaged in any reasonable life of a bicycle.

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    Spokes at 40k km are not at the end of their life. Spokes have a lifetime of at least 300k km, potentially infinite: yarchive.net/bike/spoke_reuse.html ...and nipples can fail during rebuild but they are cheap to replace.
    – juhist
    Jun 18, 2022 at 8:07
  • ...and if you have used spoke length calculator, you have noticed that the flange doesn't need to be "exactly same flanges". Spoke length in common spoke patterns is fairly insensitive to flange measures. A close enough flange, which it usually is, is enough.
    – juhist
    Jun 18, 2022 at 8:08
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    @juhist That thread was regarding replacing the rim. From the same author as the archive post you linked to: sheldonbrown.com/brandt/reusing-spokes.html "The reason a bike shop would not choose to do this is that they do not know the history of your spokes..." and "The spokes should, however, not be removed from the hub...."
    – mattnz
    Jun 18, 2022 at 20:53
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Having to re-adjust the rear cones weekly on my low-end Halfords bike, I decided to strip it down. The cup races and cones were significantly worn.

After some research I found an E-Bay seller offering a complete new hub assembled with cones onto a quick-release axle (no skewer) for £17.50.

I also find Halfords sell a complete rear wheel for £27.50. Experience has shown me I'm incapable of re-building a wheel properly so I would have to pay someone to do this. I estimate £20.

The "repair" total would be £17.50 + £20 = £37.50
The "replace" total would be £27.50

I guess your bike shop was right.

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  • Weekly, jeez! I replaced my hubs/wheels after 10 years, about 50,000 km, of otherwise no-maintenance at all Maybe rethink whether you want low-end bike. My bike cost 700 12 years ago, maybe 1600 now -- I justify/budget that as being less than the cost of one year of public transport. I depend on it for multi-hour rides and for everyday commuting.
    – ChrisW
    Aug 27 at 19:11
  • In the West, the labor to lace up a wheel is probably more than $/£/€20. You usually need new spokes and nipples, so additional cost there - the spokes do get bent a bit in the process of unlacing the wheel, and in fact a lot of people just cut the spokes, as it's faster than unthreading the nipples.
    – Weiwen Ng
    Aug 27 at 19:46
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  • If it is a carbon wheel it is worth rebuilding with new hub:
    • If it is only the bearing has worn out, just replace the bearing and keep using the wheel without rebuilding
    • If the worn-out part are not just the bearing but the spoke holes, hub, case, etc. you should replace it with a new hub and rebuild it
  • If it is an aluminum rim, just leave it alone and go to buy a brand new wheel.
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Replacing a hub does not mean replacing the spokes. Hub flange sizes are pretty standard. If you have for example a Shimano rear rim brake 135mm freehub for 36 spoke holes, you can usually put another Shimano rear rim brake 135mm freehub and use the same length spokes.

If the spokes have been time-tested, they are better than new, since a new spoke may occasionally (although rarely) have material issues, resulting in some spokes failing early. Your spokes have demonstrated that they have no material issues, if you pick new spokes you can't be certain of that.

However, if hub bearings have failed this does not automatically mean the hub has met its end of life.

If the hub is a loose ball bearing hub like what Shimano sells, it may be that the bearings just need tightening. Check if this is the case and while you're at it, disassemble the hub and look at the quality of cups, cones, bearing balls and replace old grease with new.

It may also be the case some bearing balls have failed. If this is the case, you just put a new equal number of balls in. If there's a ball retainer, it may be replaced with a suitable number of bearing balls of the same size, but assembly without retainer is bit trickier (although not too difficult).

It's also possible bearing cones have failed. In some cases, you may find a replacement cone although it has to be compatible with the old hub, not all cones are compatible.

If a bearing cup has failed, it may be replaced too although you will require some special maybe improvised tools to do that. The cups are press fit. However, the only guarantee of a suitable replacement cup is by buying a new identical hub and cannibalizing it for the bearing cups. That requires less work however than a wheel rebuild so it may be worth it.

If the hub is a cartridge bearing hub, you may replace the cartridge bearings with identical ones. The bearing cartridges are standard parts, replacement parts are very easy to find, but replacing those bearings requires specialized tools, they are press fit.

If the hub is a cup&cone hub with a failed cup or cone and either a replacement cup or cone cannot be found, then in that case the only option is to replace the entire hub. You may reuse the rim always (assuming you selected the same number of spokes for the new hub), and spokes if the new hub has approximately the same flange specifications.

Keep in mind that if you buy an entire new wheel, a human or machine has to build it from the scratch. If it's human who builds the wheel, you're not saving anything by buying an entire new wheel instead of removing the old hub and replacing with the new hub, since in that case you have to pay for new spokes and new rim.

If you find a new machine built wheel, that could save some money, but beware: most machine built wheels are poorly built, so it's very common for heavyweight riders to cause a total and complete loss of tension in the entire wheel, requiring a human to fix it. If you're not heavier than 70 kg, then you may find that some machine built wheels may be acceptable.

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    Re. your first sentence, the reasoning in the OP was about "relacing" (not "replacing") the spokes, i.e. just rebuilding the wheel around a new bug. And yes the idea of "canibalizing" a new hub for its parts, to replace into the worn hub, was what I was asking about.
    – ChrisW
    Jun 17, 2022 at 20:14

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