How to tell if a hub uses sealed bearings or loose ones?

Question

My rear hub is dead. Tt has tons of play and I'm planning to replace it with  a  new Shimano  one. Everyone suggests me to  get one  with sealed bearings,  how can I tell if a hub uses sealed or  loose bearings? For example I'm planning to buy this one:
Link to Shimano  hub

is there any naming scheme so I can tell by the  name?
where can I verify that?

thelawnet · Accepted Answer

Refer to the Shimano website for diagrams and specs
exploded diagram via
https://si.shimano.com/
https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-T610/EV-FH-T610-3515.pdf
Note
Steel Ball (1/4") 18 pcs
Left Hand Seal Ring
Right Hand Seal Ring
Refer here:
https://productinfo.shimano.com/#/spec/TREKKING/FREEHUB%20(Rim_Disc%20Brake)
As you can see there and here
https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-T3000/EV-FH-T3000-3890A.pdf
compared with the cheaper FH-T3000
If you refer to the full parts list & spec you can see that the axle is the same, but other parts are different, including more/better seals on the T610
Some other bits from the spec:

CBN - cubic boron nitride - refers to the finish on the bearing race (Shimano only)
Free hub body - steel this makes it heavier, but the design of HG freehub bodies means steel is usually better because the splines are vulnerable when using (more expensive! aluminium)

Shimano have discontinued the higher spec T780, which uses smaller ball bearings.
https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-T780/EV-FH-T780-3176.pdf
This is generally reckoned to be Shimano's most durable design:
https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-M756/EV-FH-M756-2099C.pdf
the FH-M756; note that there is a new, downgraded version, FH-M756A.
M756(A) uses a large flange diameter, which makes the wheel stronger (with reference to things like spokes breaking). It's quite heavy, compared to newer designs.
Note that:

M756 is a six-bolt disc hub, the others listed are centerlock, so that's an issue for those with centerlock discs as you'd need an adapter
Your T610 is way above the quality of standard $800 bike freehubs, which will tend to be more like the T3000 I linked above, or even cheaper versions with worse sealing https://si.shimano.com/api/publish/storage/pdf/en/ev/FH-RM35/EV-FH-RM35-3250A.pdf
People telling you to get sealed bearings (presumably cartridge bearings) are simply wrong - cartridge bearings are a valid choice, and they are easy to replace as they are a cartridge rather than loose balls, but they are not better per se. Rather, 'boutique' hub makers will have lower manufacturing costs with cartridge bearings, compared to Shimano producing loose bearing freehubs. So there are lots of people with a vested interest in promoting cartridge bearings.
Lots of expensive freehubs are prone to failure as they are sold on lightness, not strength, and the use of aluminium on freehub bodies and axles makes them much less durable than a quality Shimano loose bearing unit made from steel.
Very expensive Shimano freehubs have more and smaller balls, which won't help durability but perhaps shaves off weight.
A Shimano freehub is designed to be packed with lots of marine grease, so that it rejects water.
Modern Shimano freehubs of 'M' type are sold on weight and 'degrees of engagement', a marketing feature referring to how quickly the freehub mechanism engages when you start pedalling on the edge of the precipice of doom. They are often less durable than older mechanisms; it's not sufficient to merely look at the 'groupset'.
Your T610 looks fine, but you will need to rebuild the wheel. It could be better just to buy a pre-built wheel with a better freehub built in to it.

Eray · Answer

I presume you mean loose vs cartridge bearings.
They are both sealed. High grade shimano hubs are actually pretty well sealed.
I can see cone nuts in that picture, so its loose bearings.

Weiwen Ng · Answer

Answering the part of the question about cup and cone versus cartridge bearings: almost all hubs use cartridge bearings. Shimano is an exception, but they make good bearings.
As already discussed, all bearings have some type of seal or shielding. For cartridge bearings, this is built in to the cartridge, which may be why people commonly call these sealed bearings. For cup and cone hubs, the seals are part of the hub.
From the user perspective, there may not be a strong rationale for choosing one bearing type over another, controlling for the quality of the bearings and the seals. Cup and cone hubs are considered to require regular maintenance. In contrast, with cartridge bearings, you typically run the bearings until they degrade, then you replace the bearings entirely. However, note that some higher-end cartridge bearings are designed to receive regular maintenance; usually this means the seals are designed to be removed and reused, or the manufacturer will make replacement seals available.

Vladimir F · Answer

Shimano hubs normally use loose ball bearings, but they are not bad at all. Just wait for juhist, he will surely explain to you in many details :)
Cup and cone bearings however require to be periodically set to the right preload. It is not difficult at all and does not have to be done way too often. Bike shops will do it in their routine check-ups.
Or if not periodically, than at least once and then they require periodic checking whether there is no play or grinding in the hub. If there is some, the preload must be adjusted.
From time to time (but measured often in years) it is also good to clean the hub, and the balls and to re-grease it. Ot can be done by your bikeshop.

Argenti Apparatus · Answer

There is a possibility your hub is not dead. If you currently have a cup and cone (loose bearing) type you can adjust the play in the bearings by tightening the cones. You may also be able to re-grease the ball bearings.

Answered by Argenti Apparatus on December 29, 2020

How to tell if a hub uses sealed bearings or loose ones?

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