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Old 08-17-06, 01:11 AM   #1
Pele
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Damaged Hub Races Metallurgy Question for Expert Mechanics(w/pics)

Well, since I got my first road bike over 3 years ago (a used bianchi trofeo), I've been overhauling my hubs about once a year but my rear hub clearly gave up the ghost as the pictures I've taken show. I can say somewhat confidently that I know how to tighten the locknuts to allow just the tiniest amount of play as I was taught by a mechanic with many decades of experience. But at some point my bearings began digging out the races and I'm embarassed to say I didn't notice it until one day I felt a lot of play in the wheel. So I tightened the locknuts but then I could notice the hub not rolling nice.

As can be seen from the pics, the bearing races are pitted with signs of rust. Perhaps the rusting started during the previous owner's time with the bike.

Q1: What are the bearing race surfaces? The surfaces are black which makes me wonder if its just hardened steel. But I wonder if they somehow polish the surface or something.

Q2: All the races were pitted (see pics) except the cone from the non-drive side. As you can see from the photo , its surface has a more smoother wear "path". Is this the appearance of normal wear? Does the black coating on the races normally get worn away to this polished silver ring where the bearings are contacting the race?

Any comments/info on hub materials, i.e. what kind of steel are they made of, would be appreciated.

thanks!
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Old 08-17-06, 02:51 AM   #2
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Appears to be the result of contamination and not enough pre-load.
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Old 08-17-06, 02:57 AM   #3
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Looks like it's time for a new hub. How old and what kind of hub is it?

Tim
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Old 08-17-06, 07:46 AM   #4
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Rust in the bearings. hmmm. To me that would indicate that non-waterproof grease, or not enough grease was used. I made that mistake once, the first time I rode in the rain, the grease washed out of the BB, not a pretty sight.

The cones are hardened steel, as should be the races in the hubs. They will wear into a polished finish where the bearings meet the surfaces. The wear area should be small and smooth. No dents(usually seen in the headset), ripples, waves, or other irregularities. It is possible that the bearing surfaces could be repaired, but it would cost much more, in time and money, than a new set of wheels. Time to upgrade.
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Old 08-17-06, 08:20 AM   #5
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Do you do the bearing adjustment with the QR tightened over the ends of the axle?
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Old 08-17-06, 10:40 AM   #6
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I used Park Tool grease which is supposed to be waterproof. How much grease would you recommend?

Tim, it is an old bianchi 8spd avanti hub. I already purchased an 8spd campy athena rear hub and built it up. Lucky find on craigslist.

One thing I remember is that there was some sign of rust in the grease on the non-drive side, but not in the drive side. However, looking at the disassembled hub, clearly there has been rust on both sides in the past.
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Old 08-17-06, 10:46 AM   #7
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"Do you do the bearing adjustment with the QR tightened over the ends of the axle?"

No, I don't.
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Old 08-17-06, 10:56 AM   #8
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Quote:
Originally Posted by Pele
Q1: What are the bearing race surfaces? The surfaces are black which makes me wonder if its just hardened steel. But I wonder if they somehow polish the surface or something.

Q2: All the races were pitted (see pics) except the cone from the non-drive side. As you can see from the photo , its surface has a more smoother wear "path". Is this the appearance of normal wear? Does the black coating on the races normally get worn away to this polished silver ring where the bearings are contacting the race?
Yes, bearing races are hardened steel. I'm not sure of the particular alloys or heat treatments used... rec.bicycles.tech would probably be a good place to ask for that kind of detail as there are several metallurgical experts on there.

The smooth, shiny ring is indeed the appearance of normal wear. Any used but not damaged cup-and-cone bearing will show this wear. It's basically harmless and if you replace the balls, relube, and readjust, it will be as good or new. Some cheap cup-and-cone bearings apparently *rely* on this wear pattern to "break in" the bearings; since the races aren't made to very exact tolerances, they are supposed to actually get smoother as the balls start to wear them in.
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Old 08-17-06, 11:02 AM   #9
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Quote:
Originally Posted by Pele
"Do you do the bearing adjustment with the QR tightened over the ends of the axle?"

No, I don't.
That could be your problem. If you set the bearings with the right preload / clearance with the QR loose, when you tighten the QR with the wheel on the bike, the axle gets compressed ever so slightly, increasing the preload / reducing the clearance.

Here's Sheldon B.'s take on it: http://sheldonbrown.com/cone-adjustment.html
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Old 08-17-06, 03:54 PM   #10
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Looks good to me except for some minor rust. There are no pits or rough spots, at least from the photos you posted. Just check all the way around on each "polished" ring of each cup and race ,and if its even, with no pits, repack with new balls, and make sure the adjustment is on the tight side, never loose.
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Old 08-17-06, 03:59 PM   #11
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You should have it just right, not tight or loose. They are both bad.
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Old 08-17-06, 04:00 PM   #12
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Looks good to me except for some minor rust. There are no pits or rough spots, at least from the photos you posted. Just check all the way around on each "polished" ring of each cup and race ,and if its even, with no pits, repack with new balls, and make sure the adjustment is on the tight side, never loose.
Are you kidding? There are huge pits in the right-side cone, in the third photograph. I agree that it's mostly just rust on the cups, at least that's all I can actually see in the photos... but there's definitely major pitting on that cone.
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Old 08-17-06, 06:03 PM   #13
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also some stress cracks in the first photo. I say time for new hubs.

I have boats, so for most bearings on the bike I use light marine grease, works well, and is 100% waterproof. I ride a lot in the rain, and have never had any rust issues.

ken.
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