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Sealed bearings 101

Old 11-14-14, 10:18 PM
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Sealed bearings 101

Hello all,

Does anyone have any good resources they would like to share regarding everything anyone ever wanted to know about sealed bearings? I'm wondering about pitfalls in replacing sealed bearings on alot of current wheelsets out there. Where are there good resources on getting quality bearing too?

Any other questions or comments regarding bearings are most welcomed here.

Thanks in advance on reading this and any comments you may have.
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Old 11-14-14, 10:47 PM
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This site has a bunch of data on bearings in general: look on the left side for a series of short essays McMaster-Carr
Since bike wheels generally stay under 600rpm (bents with small wheels might be upto 1000rpm, but not 700c wheels) bearing quality is not really
a major concern. Mcmaster bearings will be very high quality, but I usually go to VXB which has reasonable costs, though their web page sort of sux.
Ceramic bearings add very little to a bicycle unless you spend a lot of time above 40mph and someone else buys your bike, clothes and sends you
a check every two weeks for riding the bike. Replacing wheel bearings mostly means having some tubing the size of the inner race for placing on axles
and outer race if placing in a recess. A press is nice but gentle tapping with a non metallic driver will work. Removing bearings is a matter of applying
pressure to the axle will allowing the bearing on the opposite side to extrude then gently tapping out the remaining bearing with a soft rod through the
hub housing. It is not rocket science and there are bunches of youtube videos.

Note: the wheel rpm given are about 45mph for 700c. Yeah I know you can get 60+ in Kali but most of us stay under 50.

Last edited by sch; 11-14-14 at 10:51 PM.
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Old 11-14-14, 11:23 PM
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The old Sutherlands manual has good basic info about design and working with. But there are different design categories. Most are radial contact and this is what most talk about. But some are angular contact. This is an important difference to understand and the resulting manor to install and "adjust".

Radial contact can't carry end loads well but when well set up can survive bicycle situations very well. They like to have their inner and outer surfaces (races/tracks) perfectly aligned with each other. Often this is far harder then thought. Simple machining dimensions will drift and real life press fits vary from the ideal. These bearings can feel quite different when pressed in place as opposed to loose in hand. New bearings can be damaged by poor installing practices. There are many times that I decide to just pull off the seals, flush out the rolling elements and squeeze fresh lube into the bearing before reinstalling the seal. Rather then replace the bearing.

There's a lot more about bearings WRT bikes but it's late. Andy.
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Old 11-15-14, 12:14 AM
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The seals in radial bearings are dust shields. They will not do a great job of keeping water out. "Sealed" Bearings by Jobst Brandt
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Old 11-15-14, 09:13 AM
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Exception is the seal type for submersible pump's bearings, which is what Phil wood says is part of their bearing specifications..

A submersible pump is a handy tool if the basement flooded.
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Old 11-15-14, 09:36 AM
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yet there is a thread out there about a bike's Phil BB being under water, in the Bb shell, and suffering for it. I've learned that water will get into any and everything it touches in time. Just aske good old mother earth. Andy.
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Old 11-15-14, 09:38 AM
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Pop the seals out and add fresh grease when in doubt.
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Old 11-15-14, 11:00 AM
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Which is what I said in my first post. Andy.
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Old 11-15-14, 11:07 AM
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Look up ABEC ratings for bearings. These are grades from 1 to 9 based on bearing tolerances and higher numbers have tighter tolerances. However, be careful about over-specifying for bike use. The cost goes up pretty fast as the grade increases but the utility for bike applications does not. There are other ways of spec'ing bearing quality but ABEC is a common one.
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Old 11-15-14, 12:30 PM
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Originally Posted by fietsbob
Pop the seals out and add fresh grease when in doubt.
Is it really that simple? Given that alot of wheels out there are using cartridge bearings, servicing them as easy as "popping the seals out."? Just be careful removing the seal?
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Old 11-15-14, 12:39 PM
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Phil Wood is another great source for bearings that will fit many hubs. I am more of the school to replace instead of trying to service these.
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Old 11-15-14, 12:50 PM
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Originally Posted by User1
Is it really that simple? Given that alot of wheels out there are using cartridge bearings, servicing them as easy as "popping the seals out."? Just be careful removing the seal?
Reading the article that davidad cited, it seems that seals of some cartridge bearings are not easy to remove.

I guess the short answer is that each component has a different service need. Shimano hubs use cup and cone bearings, whereas Shimano BB's use cartridge bearings. When the BB has a problem, you replace the entire unit. Easy enough. Labyrinth seals on Shimano hubs work surprisingly well for their simplicity, yet it makes sense to clean and regrease the hubs from time to time.
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Old 11-15-14, 12:51 PM
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All my bikes have loose bearings or caged bearings. No sealed bearings at all (except for cartridge bottom brackets, I don't know what's inside them).

But I can tell you from my inline skate days (with my now grown children), bearing quality can be detected by rolling on them. The lowest quality bearings that we used for replacements (or bought in slates after I learned the difference) were ABEC 5s. ABEC 1s were much lower quality than ABEC 5s and did not last as long. Lower quality bearings felt looser (not as well made), and didn't roll as far, or as smoothly, and did not last as long. I have ABEC 9s in my last pair of skates, and you can definitely feel the difference in performance (how smooth they roll, and how long they last).

You don't have to buy the best, but if you do, you will be able to tell the difference. Whether it is worth the cost is another matter. A set of replacement ABEC 5s for skates was like $15, and a set of ABEC 9 was like $50-$75 depending on the brand and where they were made. Bearings have the type/size stamped on them, and you don't have to buy replacements from the company whose name is stamped on the product (wheel?). You can look though catalogs from manufacturers, and find the same bearing type made by many manufacturers. Just be aware that you are necessarily going to get a bearing made by SKF, if you order an SKF bearing. Bearing Suppliers often substitute bearings with the same types, and bearing manufacturers often get some bearings from competing manufacturers to fill out their catalog of offerings.

It was discouraging to open two tubes of bearings that I paid different prices for (say $40 and $75) with different brand names on them and find the identical bearings with the same manufacturer and bearing type number stamped on both sets of bearings. After that, when buying bearings, I went by the price, and checked the actual bearings that were in the tubes that were for sale (not all bearings are the same, despite having the same bearing type number, I've developed a list of favored manufacturers)).

Last edited by RoadGuy; 11-15-14 at 01:04 PM.
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Old 11-15-14, 02:50 PM
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Good place to get them. REAL WORLD CYCLING AFTERMARKET COMPONENTS, BEARINGS, & SEALS
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Old 11-15-14, 03:06 PM
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The operating conditions for inline skates are very different and more demanding than bike hubs. The differences you detected on your skates would likely go unnoticed on a bike.
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Old 11-15-14, 03:07 PM
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I have only needed several sets. I have a friend that has an AC electric motor shop, does everything from little ones to stuff that has to use an overhead crane to handle. I've got every bearing that I've needed from him. I don't know what they are rated for but I am quite sure that I am not capable of duplicating the loads that AC motors put on them. All that matters to me is that I haven't ever had the first problem with one. A month or so ago I got a pair of 608RS, I think, from him. $4.40 for the pair.
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Old 11-15-14, 03:22 PM
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Originally Posted by RoadGuy
All my bikes have loose bearings or caged bearings. No sealed bearings at all (except for cartridge bottom brackets, I don't know what's inside them).

But I can tell you from my inline skate days (with my now grown children), bearing quality can be detected by rolling on them. The lowest quality bearings that we used for replacements (or bought in slates after I learned the difference) were ABEC 5s. ABEC 1s were much lower quality than ABEC 5s and did not last as long. Lower quality bearings felt looser (not as well made), and didn't roll as far, or as smoothly, and did not last as long. I have ABEC 9s in my last pair of skates, and you can definitely feel the difference in performance (how smooth they roll, and how long they last).

You don't have to buy the best, but if you do, you will be able to tell the difference. Whether it is worth the cost is another matter. A set of replacement ABEC 5s for skates was like $15, and a set of ABEC 9 was like $50-$75 depending on the brand and where they were made. Bearings have the type/size stamped on them, and you don't have to buy replacements from the company whose name is stamped on the product (wheel?). You can look though catalogs from manufacturers, and find the same bearing type made by many manufacturers. Just be aware that you are necessarily going to get a bearing made by SKF, if you order an SKF bearing. Bearing Suppliers often substitute bearings with the same types, and bearing manufacturers often get some bearings from competing manufacturers to fill out their catalog of offerings.

It was discouraging to open two tubes of bearings that I paid different prices for (say $40 and $75) with different brand names on them and find the identical bearings with the same manufacturer and bearing type number stamped on both sets of bearings. After that, when buying bearings, I went by the price, and checked the actual bearings that were in the tubes that were for sale (not all bearings are the same, despite having the same bearing type number, I've developed a list of favored manufacturers)).
Bearing makers will make bearings for people that have a bearing type number on them, but the bearing itself is made to a higher spec than you would get if you just ordered that bearing number.

This comes up from time to time in machine tool stuff, somebody will tear down something and order based on bearing number and performance will not be as good as if you ordered the bearing from the machine tool maker.

Bill
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Old 11-15-14, 07:04 PM
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I usually get my bearings at one of the local bearing houses. Cheaper and better service. These guys do bearings for a living.
I never buy bearings at the LBS or auto parts stores anymore.


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Old 11-15-14, 07:31 PM
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Originally Posted by fietsbob
Exception is the seal type for submersible pump's bearings, which is what Phil wood says is part of their bearing specifications..

it isn't true.

The mechanical seal is what keeps the water out of the bearings on a submersible pump and the bearings are open and oil lubricated in an oil chamber. Usually the bottom bearing is a set of, or double angular contact arrangement to absorb the axial loads from an overhung impeller. The upper bearing may be greased and sealed, but there's nothing special going on there.

Submersible well pump motors run filled with mineral oil.

(your plastic pump in the basement probably has greased bearings, but it still depends on a mechanical seal or packing to keep the water out.)

The bearing "number" (#6205 for example) only designates size. Sometimes the superprecision bearings carry extra marking, but not always.

Over specifying a bearing can create as many problems as under specifying one. If you put an AGMA 9 bearing in an electric motor you'll probably be very disappointed in the service life you get out of the order of magnitude more expensive bearing. It probably won't last as long as a cheap one, or run any smoother.

If you are spinning something at 10,000 rpm plus, or are trying to hold sub 0.0001 tolerances on a machine tool, yeah, you need a high class bearing.

100,000 rpm or extreme high temperatures, you might want to consider ceramics.

On a bike? I'd rather spend the money on better beer.

Last edited by TGT1; 11-15-14 at 07:43 PM.
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Old 11-15-14, 09:28 PM
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Originally Posted by TGT1
If you are spinning something at 10,000 rpm plus, or are trying to hold sub 0.0001 tolerances on a machine tool, yeah, you need a high class bearing.

100,000 rpm or extreme high temperatures, you might want to consider ceramics.
This plus RoadGuy's posting on skate wheel bearings reminds me of a posting on another bike forum years ago when the subject of bearing quality came up. The poster was also a skater and needed new bearings for his race skates so he went to a local bearing supply house. The following conversation was reported:

Skater: Give me the best bearings (of the correct size) you got.
Counter man: Sure, how many do you need?
Skater: 20
Counter man: OK, that would normally be $79 but in that quantity I can charge you $75 each.
Skater: (gulp) EACH? Wow, what are those bearings intended for?
Counter Guy: 20,000 rpm at 800 degrees.
Skater: What have you got that's good for 2000 rpm at 80 degrees.
Counter Guy: OK, those are $5 each.

As you said, be careful of over specifying.
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Old 11-15-14, 10:29 PM
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Originally Posted by User1
Is it really that simple? Given that alot of wheels out there are using cartridge bearings, servicing them as easy as "popping the seals out."? Just be careful removing the seal?
I've cleaned and repacked a lot of sealed bearings using a sharp and thin penknife blade point to remove the seals. Pry on the outer part and be careful not to bend or damage them.
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Old 11-15-14, 11:57 PM
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Originally Posted by TGT1
If you are spinning something at 10,000 rpm plus, or are trying to hold sub 0.0001 tolerances on a machine tool, yeah, you need a high class bearing.

100,000 rpm or extreme high temperatures, you might want to consider ceramics.

On a bike? I'd rather spend the money on better beer.
Originally Posted by HillRider
As you said, be careful of over specifying.
^^^THIS^^^

I looked a bit but didn't find it to copy. I got a new GXP bottom bracket and IIRC the recommeded service interval with ceramic bearings was a few hundred miles.
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Old 11-16-14, 09:52 AM
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Originally Posted by gregjones
^^^THIS^^^

I looked a bit but didn't find it to copy. I got a new GXP bottom bracket and IIRC the recommeded service interval with ceramic bearings was a few hundred miles.
Anything machine tool related I have ever seen that had ceramic bearings use velocite 3 spindle oil, which if I handed you a coffee can full you might think it was Kerosene or diesel fuel.

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Old 11-16-14, 10:42 AM
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That would explain the recommendation for frequent service. I doubt that I would have bought one with ceramic anyway, but the thought of performing that task settled the debate. No ceramic for me!
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Old 11-17-14, 11:40 AM
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Everything you EVER needed to know about bearings but were afraid to ask:
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Last edited by Booger1; 11-17-14 at 11:45 AM.
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