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Old 10-18-05, 08:08 PM   #1
tonyt
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Loose bearings! stainless or chromium

Loose bearings are available in both chromium and stainless in "grade 25" (i.e. same precision in manufacture) the only difference is a slight difference in hardness (yield stenght 295,000 psi vs 275,000 for chromium vs stainless respectively). Price differnce is small favoring chromium. What do you use and/or prefer? Experiences?

Keep in mind that neglected load bearing surfaces may corrode regardless of the bearing running in them and neglect (e.g. dirt) will ruin both.

P.S. Perhaps a new thread, ceramic bearings (a set costs as much as "cheap" hubs....... )
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Old 10-18-05, 09:11 PM   #2
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It doesn't matter. I'd most likely get the chromium since they are slightly cheaper.
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Old 10-19-05, 02:55 AM   #3
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The grade-5 or 10 would also be a good option to look into...
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Old 10-19-05, 08:43 AM   #4
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Stainless's biggest advantage is corrosion resistance. Since a bearing ball is constantly lubricated (or at least should be) this is not really important.

Some will say that SS might be good in applications that get lots of abuse (like a MTB HS) but using stainless is no substitute for regular maintenance.

Chromium is not really the best description since there's more to it than that, but that's what I prefer.
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Old 10-19-05, 09:55 PM   #5
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Originally Posted by DannoXYZ
The grade-5 or 10 would also be a good option to look into...
I've not seen these except in ceramic and they were ca. $4 each for 1/4". Do you know of a source for "steel" ones?
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Old 10-20-05, 12:57 AM   #6
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Ceramic does have twice the hardness of steel balls, but the extra cost isn't really worth it. It's main benefit is high-speed operation where heat causes problems with steel balls; not something you'd encounter in a bike. The hardness of a bearing isn't as important as it's precision, the rounder the ball, the tighter you can adjust the cone. The less slop and wiggle they'll be and the longer lasting the whole assembly will be.

Try this outfit: McMasterCarr.com, enter "steel balls" into FindProduct box. The "M-50 Tool Steel Precision Ball" is a good value in a grade-10 bearing.

Another outfit is Salem Specialty Balls. Their chromium balls can be had in grade-1000 up to grade-5. And 440 stainless balls usually come in grade-100 up to grade-5.

I've used TRD Specialties before as well.

BTW - "chromium" balls typically have less than 2% chrome, while "440 stainless" has about 18%

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Old 10-20-05, 05:41 PM   #7
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Originally Posted by DannoXYZ

BTW - "chromium" balls typically have less than 2% chrome, while "440 stainless" has about 18%
I think it implies that they are chromium plated (which I'm not sure they really are; wouldn't that peel off with wear?).
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Old 10-20-05, 06:04 PM   #8
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They aren't plated.
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Old 10-20-05, 07:13 PM   #9
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Here's a link to a bearing industry website that I use from time to time. It's really oriented toward engineers who design machinery and specify industrial bearings, but should be of help to anyone with an interest.

http://www.bearingsindustry.com/Index.htm

I believe the "chromium" you are referring to is the amount of chrome in the steel, designed to impart specific mechanical properties, and does not refer to plating. Plating generally would not hold up to the high loads and dynamic stresses that ball bearings are subjected to. Many cyclists are familiar with the term "chromoly" in reference to steel frames - an alloy of chrome and molybdenum. Stainless alloys are not generally, though not always, as "tough" as chrome-molybdenum alloys. This is quite a simplification, though - metalurgy is a rather deep and often mysterious science, even to engineer like me who studied it for (short) awhile. Chrome and nickel, in various amounts, are the prime additives in making plain steel into stainless steel.

As for ceramic bearings - ceramic is a very strong material, but is also quite brittle, and not very "tough" compared to ferrous materials like steel. Toughness is actually a word used in metalurgy, and really is quite self-explanatory. Ceramics are low on the toughness scale. It's quite easy to understand why bearings need to be tough. My greatest familiar with ceramic bearings are in applications subject to very corrosive conditions and low loads - more as in sliding and rubbing applications, not where roller or ball bearings are typically used.
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Old 10-20-05, 10:12 PM   #10
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Quote:
Originally Posted by DannoXYZ
Ceramic does have twice the hardness of steel balls, but the extra cost isn't really worth it. It's main benefit is high-speed operation where heat causes problems with steel balls; not something you'd encounter in a bike. The hardness of a bearing isn't as important as it's precision, the rounder the ball, the tighter you can adjust the cone. The less slop and wiggle they'll be and the longer lasting the whole assembly will be.
don't you reach a point of "weakest link" somewhere between here and there if the races are not machined to as tight of tolerances?
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Old 10-20-05, 11:20 PM   #11
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Sometimes it's good to think out loud, sometimes it's not.
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Old 10-21-05, 06:31 AM   #12
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Sometimes it's good to think out loud, sometimes it's not.
care to elaborate out loud?
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Old 10-21-05, 11:06 AM   #13
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Originally Posted by dafydd
don't you reach a point of "weakest link" somewhere between here and there if the races are not machined to as tight of tolerances?
Correct. Tolerances are stacked so that any piece of equipments accuracy is only as good as its worse tolerance. High percision bearings such as ABEC Class 9 requires the shafting and housings to be machined to the same percision class. Putting Class 9 bearings onto shafts and housings machined to class 1 nets you an overall accuracy of class 1. Acutal bearing performance will initially be high, however in short order a degeradation of performance will occur as the bearings are asked to absorb the lower percision shafting and housings

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Old 10-21-05, 05:23 PM   #14
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Stainless alloys are, to make it really simplistic, the trading of carbon for chromium. The more Chromium a steel alloy has and the less carbon, the fewer carbides can form during heat treatment. In other words, stainless steels, for the most part, are softer than carbon steels (those with little chromium and more carbon.) You would be better off with less chromium in your ball bearings. Yes, there are exceptions to everything I've said but I think it's a fair description for bicycle ball bearings.
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Old 10-22-05, 04:15 PM   #15
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Ditto fmw's comments...

Stainless steel is nearly always softer than carbon steel. Stainless steel in my mind is a lousy bearing material.

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Old 10-22-05, 07:11 PM   #16
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Quote:
Originally Posted by dafydd
don't you reach a point of "weakest link" somewhere between here and there if the races are not machined to as tight of tolerances?
Yeah, you go get to a point where overall tolerances won't improve with more precision in some of the components. But you still get to adjust them a little tighter and the high-spots will face higher point-pressures which will eventually wear them down more than other spots. Eventually the +/- tolerances will improve with wear, then replace the bearings to restore tigher tolerances.

The first time I installed a Campy Record BB (which comes with grade-10 bearings), it lasted about 1-year before requiring an adjustment. After I overhauled it and replaced with new grade-10 bearings, it lasted over 2-years the next time.
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Old 10-22-05, 10:13 PM   #17
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care to elaborate out loud?
Sure. When one expresses, either verbally or in writing, a concept of dubious or uncertain accuracy in order to validate said concept, one risks villification.
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Old 10-23-05, 10:22 AM   #18
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Sure. When one expresses, either verbally or in writing, a concept of dubious or uncertain accuracy in order to validate said concept, one risks villification.
thanks for pointing out one of the weak points of desseminating or questioning any piece of information.
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