Wheel servicing - what do you do?

Wheels with cup-and-cone bearings: Regular check of bearing play and adjustment if there's something less than perfect (i.e. can feel more or less than a tiny amount of lateral movement at the rim, or gritty feel or tightness of the axle when the wheel is out of the bike). Occasional clean and re-grease, when the bearings don't feel quite right. I grew up with cup-and-cone bearings, there's an art to getting them just right.

Wheels with cartridge bearings: Replace bearings when they feel rough.

It depends, in part, on the bearing type and quality. But also on the amount and type of use you put the wheels to.

Cup & cone bearings, as used by Shimano and in many older wheelsets, are most likely to get problems unless they have some sort of sealing to prevent the ingres of water and grit. Many cup & cone designs are relatively open to the elements but others have sealing caps or flexible rings/grommets to keep the wet & muck out.

You can check two things: any tightness or play when you spin the wheel or push it side to side when tight in the dropouts; any noise or feeling of graunch when you use a finger or (better) listen to a screwdriver by placing its blade on the hub-end and the handle on your ear as you spin the wheel.

Wet, rust and grit have to be dealt with quickly in cup & cone bearings as, if they aren't, the bearing surfaces that are an integral part of the hub shell in many designs will wear/pit. These can't be replaced except by replacing the whole hub and rebuilding the wheel.

Wheels using cartridge bearings can more easily survive a bearing going bad as the whole bearing can be removed and replaced with new cartridges, of the same or perhaps better brand but same size. Although cartridge bearings come sealed (the balls and races protected with thin rubberised shields on both sides) some seals are better than others; and some conditions of riding more readily overcome the protection of the seals against dust and water.

Although you can carefully remove/replace the out-facing seals to clean and regrease such bearings that you feel may have got water or dust in, its easy to damage those seals. Replacements can be got, if so. For example, Hunt wheels will provide new seals if you damage those on their wheels whilst cleaning and regreasing the bearings.

You can feel or listen for cartridge bearing wear in the same way as you can with cup & cone bearings. Many people avoid cleaning/regreasing them, as mentioned above, if wear or graunch is detected, since they can be relatively inexpensive to replace. A commonly-used good quality 6802 wheel bearing cartridge costs about £6, although you can easily pay a lot more for better quality. Whether such better quality gives you much advantage is a moot point. They'll still wear if wet or dust get in and aren't quickly cleaned out. But they may have much better seals.

To take apart and reinstall cup & cone bearings, you really need only one special tool type - cone spanners, which are very thin and sized for a variety of nut and cone sizes found in such bearings.

To take out and replace cartridge bearings, you need either a drift and a hammer or a bearing puller, as well as a correctly-sized bearing press to put in the new bearings. No need to remove the bearings, though, if you think you can bring them up to spec with a clean and regrease - i.e. before any significant wear or damage has occured after they feel stiff or noisy (graunching or squeaking). Take off the seals and clean/regrease the balls & races carefully, in situ within the wheel hubs.

Using a drift and hammer to remove bearings is likely to damage the races (brinneling or denting the races with the balls from the hammer-shocks). You might be able to re-use extracted bearings if you use a puller (which still needs some hammer taps) as the hammer taps are more controlled, as is the distribution of the removing-force on the bearing, so the bearings might survive. But it's safer to replace them with new, once knocked out.

If you do regrease bearings, don't pack the grease into every space available, as this causes a lot of drag on the bearings. The general recommendation is to fill 1/3 - 1/2 of the air spaces around the balls and races; and with a grease that isn't thick but not so thin that it becomes an oil when the bearing goes 'round and heats it up.

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If you're an obsessive you can perform on ongoing wheel-spin test for bearing wear.

When new, the wheel will spin for the same initial impetus for N revs before coming to a stop.

As the bearings "bed-in" and the grease distributes in them, the same intial impetus will see the wheel gradually spin a few more revs before stopping. This condition should be reached in a couple of hundred kilometres from new.

Later on, the same impetus might start to see the wheel rev even more before coming to a stop. This is due to the grease begining to degrade, lessen, migrate off the bearings interfaces, etc. so that it ofers less resistance to the still-good bearings as they spin. It would be a good time to consider ading a bit of extra grease, if you can be bothered to prise off the seals to get it in, then replace the seals without any damage to them being done.

Even later, if the number of revs begins to decrease again, the liklihood is that grease is insufficient and the bearing is "drying out"; or rust and dust have got in and worn the bearing. Time to replace them. 

https://www.hambini.com/support/bearings/bearing-service-lubrication-gre...

https://help.huntbikewheels.com/support/solutions/articles/43000558015-b...

https://ceramicspeed.com/en-eu/pages/bearing-cleaning-maintenance?mdApp_...

https://www.hambini.com/grease-for-bicycles-a-practical-guide/

https://www.bearingprotools.com/collections/bearing-pullers-single

If you're running conventional bearings (e.g. Shimano)  then an annual clean and regrease won't come amiss.