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Bearings compatibility

Old 01-28-19, 05:03 AM
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Bearings compatibility

Hello.

Time to change the bearings in hub and wheels but I can't find the same brand with the same measures (6902, 6903). In order to replace the bearings, is it just enough to choose the right measures without any further considerations?

The bearing to replace are LBLU type, I don't know exactly what it means, I guess it regards the type of seal, while usual is 2RS. I know there are some other characteristics to bear in mind, like tolerance and ABEC scale, which seems to be 3 for bicycles.

My fear is that the bearings I purchase, although the same measures, will not perform good enough as current ones, not because of quality difference but because some other reason.

I'm attaching a picture of one of the bearings, disassembled.

Thanks.
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Old 01-28-19, 06:24 AM
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Compared to general machinery, bicycle bearings tend to have an easy life.
Match the number(6902 etc) and the seal type and you should be good to go.
MTBers sometimes develop preferences WRT which brand shows best resistance towards contamination, but it’s generally not a huge deal.
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Old 01-28-19, 07:28 AM
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Buy the same size bearings by a reputable maker (SKF, Timken, etc) and you should be fine. ABEC 3 is plenty and specify the seals. It looks like your previous bearings lived a difficult life.
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Old 01-28-19, 08:37 AM
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So that bearing customers don't go crazy, bearing manufacturers have standard sizes. So 6902 and 6903 each specify exact, consistent sizes and types (both of these are what are called "deep groove radial ball" bearings). So any 6902 bearing should physically replace another 6902, as far as the physical size.

There are bearing classes, with a higher number reflecting tighter runout and concentricity. So ABEC-9 has better specs than ABEC-3. As dabac points out, this precision difference may not be an operational concern for a bike wheel. And, as you correctly point out, most bike bearings are ABEC-3, which is a perfectly good grade.

There are tolerance and preload specs. This refers to how "tight" the bearing is at room temperature and allows users to select a bearing that will work properly after its up to speed and warmed up. So you can get C2, C3, and so forth. Most bearings are "CN", which is between C2 (tight) and C3 (looser). You probably don't have to worry about this.

The LBLU does indeed stand for seals: one "LB" and one "LU". This is not super-common terminology, but I suspect it refers to what is more often labeled LLB and LLU. An LLB seal is a metal-backed rubber seal that is fastened to the outer race, and does not contact the inner race. An LLU seal is also metal-backed rubber but is fastened to the outer race and contacts the inner race. The former gives lower friction but lower sealing integrity, the latter has more friction and better sealing. If the picture you show really is your bearing, the sealing didn't work too well. That's a pretty rough bearing.

Enduro sells bearings for bikes, and they use a slightly different terminology. Their LLB does make contact, but to a lesser degree than their LLU. Enduro LLB and LLU seals have grooves machined into the inner race for this inner seal. Standard metal-backed rubber seals (RS type) just contact the bearing surface with no groove. I use Enduro LLB bearings, but that said I think that you probably would be fine with inner and outer RS type seals. That is, I use 6902 or 6903 LLB but I think that two RS type seals (2RS suffix) would work. More info here.

Historically, bearings were loose inside an angular contact cup and cone setup. One would maintain wheel bearings by taking them apart and cleaning off dirt and old grease in the cup and cone (and possibly the balls) and then repack the bearings with new grease (and possibly with new balls). You can pull the seals off of some cartridge bearings and can then clean them using solvent of some sort, and then repack them. Given your picture, your bearings are shot and this is not an option. And part of the whole point of cartridge bearings is that you just replace them, with less work than cleaning and repacking. But you can buy bearings with a snap ring (SRS) seals that are easier to pull out, which allows you to remove the seal and clean the bearing. You can also remove LLU/LLB and RS bearings, but its tedious and you can damage the seals so that they don't seal as well when you replace them.

Upshot? Any 6902 bearing should replace another 6902. Same for 6903. You could buy a bearing with LBLU seals, but these didn't work very well for you, judging by your picture. You'd probably be find with 2RS bearings seals too. I value my time, and so I pay a few bucks extra in premium to get a bearing that I'm confident will have proper design for bikes, at Enduro. These are LLB seals.

If you've been riding a bike with the bearing shown, anything you buy will be a sea-change improvement. I suspect that you do not need to shell out for ABEC-9 or ceramic bearings! But of course its your call.

Last edited by WizardOfBoz; 01-28-19 at 09:08 AM.
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Old 01-28-19, 08:50 AM
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https://www.enduroforkseals.com/index.html
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Old 01-28-19, 08:57 AM
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Hard to go wrong with something like Enduro bearings. They are tailored for bicycle use so you can rest comfortably that the seals, grease, and internal clearance are all properly speced for the application. While the bearings from a big bearing company may be superior, it's hard to say if this matters, and you will have to navigate and learn what you are buying since a lot of variables can be in play (internal clearance, grease type, and seal type for example). For example, I think for a bike we want contact type seals vs. non contact seals which can allow water to enter the bearing. C3 internal clearance is typically best for a bike part too. Too tight of a clearance will cause the bearing to fail prematurely. The devil can be in the details.

Edit: a more detailed description of what I stated was posted while I was lingering on this post. I'm not copying, honest!

Last edited by Nessism; 01-28-19 at 09:01 AM.
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Old 01-28-19, 10:12 AM
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Originally Posted by Nessism
While the bearings from a big bearing company may be superior, it's hard to say if this matters, and you will have to navigate and learn what you are buying since a lot of variables can be in play (internal clearance, grease type, and seal type for example). For example, I think for a bike we want contact type seals vs. non contact seals which can allow water to enter the bearing. C3 internal clearance is typically best for a bike part too.
+1. It takes me an hour or so to replace wheel bearings (and the first time I did it, more than that). If I find a bearing $3 cheaper, but if fails or is not quite right, that's a net loss. So I just buy the made-for-bikes bearings. YMMV.
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Old 01-28-19, 12:18 PM
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I bought Enduro 90% fill (all balls) , to replace the 6001 with a separator and fewer balls .. on my Touring Bikes Bullseye Hubs..

QBP distributes them , selling to my LBS..
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Old 01-29-19, 12:12 PM
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Thank you everyone, specially for detailed information and advice, I have learned a lot.

I was not concerned about bearings and initially planed to buy cheaper ones, but your comments have changed my mind and I have just ordered the whole set for wheels and hub, brand Enduro, 2rs-llb-abec3. I believe it is a good investment, I will ride more confident and, hope, perform better. Also I expect they will last a long time and still using them following a proper maintenance.

The bearing in the picture was seized, the only one of all 6, but I believe it was faulty from the beginning because the rear wheel always sounded like a very light "clonk" when laterally shaken. I have recently learned that it is not normal and I am afraid the seller of the bike cheated on me. Let's see it the "clonk" is gone after assembling the wheel with the new bearings. That's the reason the bearing is so much damaged. I think the remaining bearings are still reusable although I will keep them just in case I have some emergency; they only have rolled 3700kms.

Last edited by patricio.montes; 01-30-19 at 01:11 PM.
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Old 01-30-19, 08:51 AM
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I question the assumption that a "bad" bearing was the reason the photo shows rust. I also suspect that the bearing shown had a bunch of side play/slop. After all rust is an abrasive. But replacing the bearings will change more then just the initial condition of the bearings. Andy
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Old 01-30-19, 01:10 PM
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Originally Posted by Andrew R Stewart
I question the assumption that a "bad" bearing was the reason the photo shows rust. I also suspect that the bearing shown had a bunch of side play/slop. After all rust is an abrasive. But replacing the bearings will change more then just the initial condition of the bearings. Andy
There is no rust, the photo is just bad quality (poor light conditions). The bearing is seized, the grease is lacking and "burned". But you are right, the bearing is not "bad", but badly assembled. I hope to do a good job, first time 😨. Still waiting for the bearings to arrive.
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Old 02-06-19, 05:49 AM
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Enduro bearings seized after assembled into hub. They rolled smoothly before and after being inserted (using a press, no hit, no tap), but I had to force a little bit to insert the axle, after that they feel seized. I will probably reuse the old bearings and will try to get a refund.

UPDATE: Still trying, maybe bearings are too pressed.

Last edited by patricio.montes; 02-06-19 at 08:58 AM.
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Old 02-06-19, 11:22 AM
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Originally Posted by patricio.montes
Enduro bearings seized after assembled into hub. They rolled smoothly before and after being inserted (using a press, no hit, no tap), but I had to force a little bit to insert the axle, after that they feel seized. I will probably reuse the old bearings and will try to get a refund.

UPDATE: Still trying, maybe bearings are too pressed.
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Old 02-06-19, 12:00 PM
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Originally Posted by WizardOfBoz
........ So I just buy the made-for-bikes bearings. YMMV.
I didn't think there were any " made for bikes bearings", thought with the bazillion bearings made for industry bearings used for bikes were cherry picked from those existing. Comments??

regards, Brian
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Old 02-06-19, 01:21 PM
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Originally Posted by calstar
I didn't think there were any " made for bikes bearings", thought with the bazillion bearings made for industry bearings used for bikes were cherry picked from those existing. Comments??
regards, Brian
Possibly not. At least "pre-selected and marketed for bike" bearings. Though I suspect that if Specialized, Giant, or Trek ask NTN of Fafnir or (especially) one of the Chinese bearing mfrs for a specific bearing, they might get it.
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Old 02-06-19, 02:12 PM
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Mine are deep groove radial contact bearing used in a hub that cannot load them in an angular fashion, from the side, so as to bind..



If you can side load them an angular contact bearing would be the choice,, and like old loose ball hubs it is possible to compress the hub axle with the QR

and side load the axle cones and the bearing balls, that way ..

so the mechanic leaves the adjustment loose which comes into adjustment when the QR is tightened, on the bike..






.....
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Old 02-06-19, 04:23 PM
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I have reinstalled the old bearings, they are in good conditions. All other Enduro bearings are already assembled into the wheels, they seem to be ok. I will return to the shop the bearings for the hub, one of them is unusable, I think it is defective.

Strangely, some of the bearings were packaged inside a sealed bag with Enduro logo, and some others inside a zipped bag with no logo, which makes me think...(bearing cost: approx. 4€ each). Probably bad luck, or most probably, newbie mechanic.

Anyway, for the next time buying cheap, use and throw, chinese bearings will be an option. But now i'll give Enduro bearings a chance.
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Old 02-06-19, 05:34 PM
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Well China does have a Space and missile program , so if something is not top quality, somebody wanted cost cutting and so some QC inspections was eliminated..
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Old 02-06-19, 10:05 PM
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Originally Posted by patricio.montes
Enduro bearings seized after assembled into hub. They rolled smoothly before and after being inserted (using a press, no hit, no tap), but I had to force a little bit to insert the axle, after that they feel seized. I will probably reuse the old bearings and will try to get a refund.

UPDATE: Still trying, maybe bearings are too pressed.
Are you sure you bought deep groove ball bearings? Deep groove and angular contact bearings both work for bottom brackets, but the angular contact bearings can be installed wrong (backward). In which case, they won't work.
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Old 02-07-19, 02:14 AM
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Originally Posted by fietsbob
Well China does have a Space and missile program , so if something is not top quality, somebody wanted cost cutting and so some QC inspections was eliminated..
Buying to China is like playing the casino: you can win more than lose if you are a good player; at least that is my approach. If it turns out that the bearing works well your investment turns to be good, if the bearing is bad you lose just 1$ each bearing. In this case a bad bearing will not harm the bicycle nor risk your physical integrity as long as you pay attention, so it worths to play. But it is very different with other components, like a carbon handlebar, that's a risky business, I have heard some really terrorific stories... I mean, China is just an option, usually I will always try to buy good components as long as I can afford it, according to the range of the bike and bearing in mind that I ride just for health and fun, not for money.

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Old 02-07-19, 02:31 AM
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Originally Posted by WizardOfBoz
Are you sure you bought deep groove ball bearings? Deep groove and angular contact bearings both work for bottom brackets, but the angular contact bearings can be installed wrong (backward). In which case, they won't work.
Radial deep groove, this one: https://www.bikeshop.es/rodamiento-e...mm/150950.html

Translated: https://translate.google.com/transla...%2F150950.html

FEATURES
Dimensions : 15 x 28 x 7 mm
Balls / needles material : Steel
Ring material : Steel
Type of joints : LLB
Type of bearing : Radial contact ball
Use : Wheels, Frame

TECHNICAL CHARACTERISTICS
- Reference: 6902-2RS-LLB.
- Grade 10 chromed steel balls.
- Standard Abec 3.
- Rings and steel cage.
- 2 joints (2RS) with double lip and minimum contact (LLB).
- Grease with high Teflon content (Rhéolube 7703).
- Weight (manufacturer): 15.7 g.

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Old 02-07-19, 11:44 AM
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Fair to say: most probably my mistake. I believe I have forced too much the bearings when pressing, or hit them lacking enough care, damaging them. The wheel feels good once assembled, but at pedaling the hub feels too seized and I can hear the balls crunch. I'll get new bearings and try again, very carefully this time.

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Old 02-07-19, 12:27 PM
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remember, you have temperature differential , as a tool, also , cool shrinks, warm expands ,,







...
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Old 02-07-19, 03:31 PM
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Originally Posted by fietsbob
remember, you have temperature differential , as a tool, also , cool shrinks, warm expands ,,
Not here, almost spring time today, 21ºC.
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Old 02-07-19, 10:48 PM
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