bowlofsalad

Hello,

I've been looking for cartridge bearings with seals (not shields) that will hold low viscosity oil instead of grease. SKF has some RSL, RS and RSH type bearing seals, but there are so many options and so little information on the subject (that I've been able to find, zero) that I have no idea what to choose. Does anyone know of bearings that would be up to the task?

I understand that better seals mean more friction.

Thanks

cny-bikeman

If you understand that why would you want oil instead of grease? Even if the net friction was less it's not going to make ANY measurable difference. The time spent pursuing fewer grams or a tiny bit less friction is better spent putting in more miles.

Wanderer

Ditto, I am confused as to a viable reason......

Mark Kelly 

You'd basically end up with hydraulic seals, which are designed to prevent leakage of low viscosity oils.

Might as well not both having the bearings, there'd be little difference in friction.

rydabent

Use grease. Dont buy into the nonsense that using oil will give you great advantage in a race.

fietsbob

find the film 'Stars and Watercarriers' 1 scene the team mechanic cleans and relubes the bearings for the Time Trial day..
(I expect they took the wheels apart & re Greased the bearings for the next road stage day)
the old Campag hubs had oil-holes but No Seals.. 3 speed S-A had no oil seals .

you just wipe off what seeps out, and add more oil in the hub ..

Rohloff's Oil seals are the same type as auto Transmissions. some still seeps out

a tight oil seal would add a significant drag.. hydraulic rams obviously use the high oil pressure to tighten the seal rings .

a Ship's Shaft packing uses the pressure of the seawater trying to flood into the engine room
to tighten the seal grip around the propeller shaft.
but there is quite a bit more horsepower turning that shaft.

BTW I greased the bearings on my AW3, it helped keep the oil I put in the gear part, there a little longer.

bowlofsalad

Does anyone happen to know of a cartridge bearing with a contact seal that will hold oil in or have decent information specifically about one?

Please do not derail this thread.

Andrew R Stewart 

No I don't. I doubt you'll find such a bearing or much info. Perhaps you should do some experimenting and report back. Andy.

ragtoplvr

There are a few automotive starters that use a wet clutch. Most of them use a spring loaded lip seal, that works very very well. ON some of them the drive end ball bearing doubles as the seal.

The only bearings we have found that keep the oil out reliably are NTN and Koyo. Real ones, the names are cloned a lot in china, almost like Rolex.

You could assume a seal that keeps the oil out would keep the oil in.

That is all I have.

Rod

FBinNY 

Just about any bearing's seal will hold with oil, not because of the seal, but because of the forces involved. Seals are (almost) always fixed to the outer race with the seal lip on the axle or inner race. As the bearing spins, oil will be flung toward the outer race, and at even moderate speeds spread itself around the periphery. When not in motion the oil will settle to the bottom half of the bearing.

So, as long as the oil level is not up to the axle or inner seal, the lower third (or so) of the bearing will act as an oil sump, and there won't be leakage. Of course, there might be some weepage if the bearing is turned on it's side, but if the seal is intact, surface tension at the gap should prevent any loss.

IMO, the ideal arrangement for this kind of lubrication would be bearings with outer seals only, and a hole drilled in the middle of the hub shell, or other method, so some new oil could be added as needed. Kind of the way bicycle hubs have been made for over a century.

Jeff Wills

I would suggest you talk to an industrial bearing house if you're looking for some special application. Most big cities have one or two businesses like this.

The bearings in bicycles are subjected to such low forces that there is no measurable difference between the "best" and "worst", so if you want to improve your bicycle I suggest you look elsewhere.

You posted the exact same question on the 'Bentrider forum: Cartridge bearing seals that will hold very light oil? - BentRider Online Forums , and got exactly the same answer.


Why not? It's the Internet, ain't it?

BCRider

You're not going to find a bike size bearing that does what you're after. First off if the seal held oil then the bearing would require an oiling hole to add the oil. And in our sizes there's simply no such thing. Systems with small bearings like our bicycles that use oil instead of grease for the bearings use sprung lip seals in addition to the bearings. And the bearings themselves are thus open styles so they can let the oil get in and out.

The seals on bearings the size we use would not hold oil anyway. They simply do not have the lip design or tension needed.

So..... you COULD use cartridge bearings and rip out the seal on the inner side and add an oiling hole and spring clip to close it similar to the old Campy hubs. The outer seal would let the oil seep out. But it would seep out slowly enough that you'd get quite a few days and miles of good lubrication. But what does seep out would make for some messy cleaning jobs.

bowlofsalad

Reliability and longevity.

Hope pro 2 evo hub uses 6804 sized cartridge bearings. You can get these bearings in sealed versions. 6804-2RS Bearing Deep Groove 6804-2RS Ball Bearings 6800-Series-Ball-Bearings

Wanderer

IMHO, a high quality grease will give you better of both - reliability and longevity.............

The only advantage of oil is less friction(drag), which is easily overshot by proper lubrication with grease, which gives you higher reliability and longevity.....

By the way - the bearing you reference, is already lubricated with - you guessed it - grease.

fietsbob

One Of Phil Wood Company's bearing Specs is a submersible pump bearing seal .

What you have in mind is a light oil for low drag, and a heavy seal drag to keep it in, in mind apparently.

.. ceramic balls and races may be another expenditure you may find worth it in the theoretical quest and big wallet budget.

cny-bikeman

Don't derail the thread? All the responses were relevant to your OP, not off-topic. If you don't want others to question the (unspoken) assumptions behind your question this is the wrong forum for you. To me, my obligation as a helping person is to give honest opinions and qualified advice, not to protect others' beliefs that in my experience may be false. In turn I expect those I help (or myself when in that position) to respect the effort and time others put in (at no charge), and if one disagrees to do so respectfully. There's a difference between choosing not to take advice or opinion and dismissing it as unworthy.

bowlofsalad

You didn't put enough periods there. Dirt, water, sand and salt all are going to mix and wash out the bearings lubrication when using a shield. You end up with either a destroyed cartridge or a destroyed cup and cone, either than or the need to replace the grease pretty quickly. I've seen this more than a few times. You have to maintain shields pretty regularly. If you ride rarely in only pristine settings, if you are racing, shields might be for you. I think most people should use seals. The discussion that I am hoping to foster relates to ideal seals(of which I have no idea) for this idea, not comparing shields versus seals.

The point of what I was linking to was to show that bearings of appropriate size exist with seals. I don't think I've ever found a sealed bearing filled with oil rather than grease. No big deal though, cleaning out cartridge bearings is very doable.
Seals require lubrication. I think this is a sorely missed idea, oil will continually lubricate a seal, grease will not.

You are right, I am sorry I was an ass, I assumed that the idea surrounding seals was very evident. In my mind, I have to wonder why anyone would use seals, I assumed it was an obvious conclusion that the idea surrounding seals related to wildly greater reliability and longevity at the expense of a small amount of friction. I guess I wasn't looking to educate others while seeking to be educated, I feel like maybe that is a bad way to look at things on my part. So, here is a chart that might help calm any skepticism to my questions and statements.

Cartridge, grease, seal: 18 N-mm @ 100 rpm to 56 N-mm @ 600 rpm
Cartridge, grease, no seal: 4 N-mm @ 100 rpm to 9 N-mm @ 600 rpm
Cartridge, 20w oil, seal: 3 N-mm @ 100 rpm to 8 N-mm @ 600 rpm
Cup and Cone, grease: 2 N-mm @ 100 rpm to 3 N-mm @ 600 rpm
Cup and Cone, 20w oil: 1 N-mm @ 100 rpm to 2 N-mm @ 600 rpm

Basically, a seal with oil doesn't lose much, but gains a lot in long term reliability and longevity, to me I see an all around sweet spot in the oil/seal idea. My theory has been that even mildly dirty bearings will cause much more friction compared to clean bearings with an oiled seal, not only will the performance be lower, but other things need replacing once things start getting dirty. I understand that grease can act as a catch, but a greases capacity for this idea is limited, a seal with oil will provide much longer functionality over a shield grease. I am not all that concerned about the higher drag, but a few months of riding through salty grimy slush will destroy a shielded cup and cone or cartridge bearing, a sealed setup is much more likely to survive and lose no next to zero performance. Again, I am not about or stuck on the performance levels(friction), primarily what I care about is longevity and reliability.

You could probably get by just fine just replacing the grease every 2-4 weeks in harsh, frequent and long riding conditions, but I really don't love that idea. All weather, dirty terrain and/or long distance riders seem like obvious candidates for much of what I am referring to.

I recommend studying hydrodynamic lubrication. https://www.youtube.com/watch?v=u5RA3zHLIdM Here is a short video on the subject, not an amazing one but it might help gain some understanding.

I have looked for studies comparing the level of friction after a year of daily riding in bearings with seals and oil and bearings with shields and grease. I am sure it's easy to guess what the outcome would be, but I'd really like to be able to quantify the results with empirical evidence. I imagine setting up two front wheels on a trike, one with an oiled seal, with with a greased shield and using that as the testing platform. It may not be a perfect test setup, but it'd probably be close enough. I haven't managed to imagine a more accurate testing configuration.

I am not saying that shields with grease is wrong or inherently bad, I think they are perfectly fine in their own right, to each their own. But for my application, seals with oil seems like a preferable route.

HillRider

I have grease lubed cup-and-cone bearings from both Shimano and Campy on all of my bike wheels and the front wheels will spin a long time and "pendulum" several times before coming to rest. If the grease drag was meaningful they would stop very quickly. If your drag units are really N-mm as shown, not N-m, then the absolute drag is so small as to be meaningless and the differences, while numerically significant, are on the order of angels dancing on a pin head. Interesting to consider but of no consequence in real life.

As to durability, I have several sets of grease lubed cup-and-cone hubs with 30,000 to 55,000 miles that are still in like-new condition with, at most, once a year or 6,000 mile overhauls. How much better life should I expect?

Booger1

Here's a lifetimes worth of bearing info:The Timken Company | Bearings & Power Transmission Manufacturer

They have info that normal folk or engineers can understand.You'll have to log in but there is ANYTHING you need to know about bearings....and plenty you don't.

demoncyclist

The factory cartridge bearings on the Gipiemme Grecal Parade wheels on my last bike (a Cannondale CAAD8 R900) had about 15K miles on them when I sold the bike to a co-worker. He has put another few thousand miles on them, with the same bearings in place. They have been through torrential rains and flooded roads for several days at a clip over the years. How much more durability do you need?

BCRider

I'd suggest that you've got a lot of misunderstanding about the realities from what you posted here.

First off oil weeps past all but the most snug seal. The seals used in bearings is not of a design that would be able to hold oil for long. Of course bearings with such seals COULD be produced but they would be larger and rather specialized. And that is why when bearings require oil for lubrication for whatever reason that they use open sided bearings with separate single or double lip seals. But such seals have a pretty high level of drag of their own even with the oil lubricating them. A level that would be quickly apparent on a bicycle with two on each axle. If you've ripped out a seal and replaced the grease with oil and figure you can use that in a bike you're sadly mistaken. The sort of seals used on the regular sealed bearings will let the oil weep out a lot faster than any normal bike rider would tolerate.

Grease allows us to run looser fitting seals that have a lot less drag. And that more than makes up for any viscous drag of the grease. But these are still seals and not shields. As someone that commuted for many years I never found that dirt got past these light shields/seals and wore out my wheel bearings or bottom brackets unless the seal broke down and left a larger opening.

Longevity and reliability? I commuted for a couple of decades in conditions where rain and grit carried up with the rain made it essential that my bikes were washed and the chain cleaned at least weekly. Otherwise it would be reduced to a sandpaper sounding hunk of mud inside of a few more days.

Even under such conditions I never found the shielded or loosely sealed Shimano MTB cup and cone bearings to be contaminated to any noticeable degree when I opened them up annually. And the annual teardowns quickly moved to bi-annual teardowns since they really didn't need anything in only 12 months. So your thought that shielded or lightly sealed hubs require attention on a more or less monthly basis in harsh weather riding conditions is wildly unrealistic. Where did you get such an idea anyway?

In any event I don't think you'll be able to fulfill your desire for proper seals and oiled bearings. I've never seen such a thing for bicycles. And if you did find anything of the sort I think you'd be dismayed by the seal drag on the axle.

Booger1

On a sealed bearing,the seal is NOT lubricated by the grease (or oil).If lube could get to the seal lip,it would be leaking and there would be no wear on the inner race.That's not the case of any seaded bearing I've seen.

On a wet type seal,there needs to be a pressure differential in order for the seal to do it's job....Think rear main seal in a car.

BCRider

On every sealed bearing I've seen the seal has a very light film of grease on it both when it comes out of the package and when I've looked at them when in use. It's not a whole lot but it's there. Wood working tools in particular will almost always have a little "beard" of greasy dust right on the seal line. So they ARE lubricated during manufacturing and from running. And yes, the grease does leak out over time. Seals wear from use and tend to leak more over time. This loss of grease is the primary failure mode for the bearings in normal use. Been there and replaced the worn and dry bearings that still had both seals in place.

The crankshaft seals on car engines are not under pressure. You're right that some seals DO rely on pressure differential but the crankshaft seals in engines use built in springs around the lip of the seal instead. The crankcase breather ensures that any internal pressure in the crankcase is vented to the air cleaner or extension from the air cleaner at a point upstream of the injector body or butterfly body depending on the engine.

On smaller seals such as we'd use on a bicycle axle the spring in the rubber itself is often enough and those small size seals often don't use a tensioning spring.

davidad

You do realize that the mechanics of that era didn't have a clue about how the bearings worked and wasted a lot of time.

fietsbob

So you were a pro team mechanic in the 70's?