Quality of ball bearings
 

Can anyone comment on the difference in quality of ball bearings. Do the no-name, no-brand bulk lot probably made in China work fine or should always buy a a box of bearing from a known manufacturer. Does it matter? It is for wheel hubs.
Thanks

You could spend 10x more for grade-10 or 30x more for grade-5 bearings and you won't notice a bit of difference whatsoever. Your bike won't ride any faster and the maintenance-intervals won't extend to 10-years. The parts won't last any longer either.

Grade 200: Carbon Steel - harder than chromium steel, but not rust resistant
Grade 25: Chromium steel is rust resistant, but requires extra additional hardening process to be as hard as Carbon Steel

So, the difference is in the corrosion resistance. BTW, the grade 25 doesn't have a chrome plating, the chromium is added to the steel mixture.

Not the entire difference. The grade refers to the "out of roundness". I don't recall the units used, but basically a grade 25 ball is 25 units (think something like .000025") max out of round, a grade 200 would have an 8 times less tolerance (.000200")

Edited for correct units - consult link at post below

Here is the difference in the ball specifications. Grade 25 is plenty good enough.

http://americandad.biz/gradechart.htm

The previous comment about the types of steel is both wrong and has nothing to do with the grade of the ball.

Plain carbon steel is the cheapest and shortest life material for ball bearings. All steels are alloys and chomium is just one of several elements added to create "chromium steel". There are a many chromium alloyed steels, but none of them is particularly corrosion resistance. You need stainless steel for for significant corrosion resistance.

The standard in the industry is Grade 25 Chromium Ball-Bearings. Which one can find here (scroll down):

http://www.biketoolsetc.com/index.cg...l%20bearing&s=

I'd suggest bookmarking this site. They have all-things-bicycle at good prices. By-the-by, Grade 25 is the best you'll find commercially available. The '25' means they are uniform in roundness down to 25/1,000,000.

Actually many chromium steels are stainless steel and some are suitable for ball bearings. The lower limit for "stainless" is about 13% Cr in the alloy and 440C stainless steel is both corrosion resistant and handenable for bearing and tool steel use.

Note "corrosion resistant", not corrosion-proof. The extremely corrosion resistant grades of stainless steel (the 300 series) are not heat-treatable and are not suitable for bearing balls in the service bicycles need.

You are correct in saying that the grade is independant of the material -- I should have been more specific in that I was comparing the material compositions of the two ball bearing offerings at the Loose Screws site.

You are incorrect as to your comments about the composition of the steels. In fact, the carbon steel bearings will probably wear better and last longer as long as they are well greased and not exposed to moisture/air. Chromium IS the primary additive for creating stainless steel. Many stainless steels have a high nickle content as well (along with other additives), and as another poster pointed out, these grades are not hardenable as the additional nickle content inhibits the formation of martensite when quenched. (High) carbon steel hardens very well when quenched, but it begins to corrode almost immediately when exposed to air and moisture.

I guess that Master's Degree in Mechanical Engineering is worth something after all.

dperreno...

I don't have a masters, only a BSME (since '81). I'm now retired. You don't need a degree to read and understand basic material properties. I'm well aware of what alloying elements are used to create stainless steels. Anyone can look those up.

I don't know how you reached the conclusion that the carbon steel balls at loose screws were harder and would last longer than the chrome steels, since neither has any specifications listed, that I could see. Any of the materials commonly used for bearing balls can be hardened to about the same Rockwell C number (typically around 60).

The grade 200 balls are probably OK for replacement of balls in cheap bike components, but I'd buy the grade 25 since they are so cheap.

Apparently, you need to learn how to read as well.

I didn't say that the carbon balls WERE harder and would last longer, I said that they PROBABLY would wear BETTER and last longer. All other things being equal, a high carbon steel CAN achieve a higher Rockwell hardness than a chromium alloyed steel through conventional hardening processes. Not by much, but higher, nonetheless. I don't KNOW that this is the case with these bearings, nor do I really care, but it IS more than just possible, it's likely, IN MY OPINION. I stand by my earlier comments.

And I'd like to point out that you were the one who "incorrected" me first. Get your facts straight and read carefully what is written before you go off and start dumping on someone.

And now I'm done with this silly discussion.

Contest!
http://www.crackunit.com/wp-content/...ll/pissing.jpg

I'd like to offer a somewhat different perspective...

No-name cut-rate Chinese products are NOT a good idea for bearings, because hardened steel is a nonequilibrium material whose hardness and other important properties depend on the exact processing protocol as well as the composition. I'm not yet entirely convinced that grade 25 is all that important (though I stick with grade 25...even grade 25 is super cheap given the amount of labor needed to do an overhaul). However, if my bearings were not made out of a nice steel like 52100 or 440C and heat treated to perfection, I'd expect that there would not be much riding between overhauls.

The difference in corrosion resistance between plain carbon steel and 52100 is negligible; you're counting on the grease to do that. Very high chrome levels are not desirable in bearings, because chrome likes to gall to itself. That's why 52100 is the standard for rolling element bearings, get most of the benefits without the adverse consequences. We've used all-stainless bearings in a few harsh applications at work where they run bathed in water-based fluids, but they never hold up as well as conventional materials where corrosion is less of a concern. Better to spend your money on grease and labor.

There are bearings made of 300-series stainless steels for service where corrosion resistance is the over-riding concern. They can't be hardened so their wear reasistance is poorer and running in an aqueous environment with it's poor lubricity makes their service life even shorter.

The 400-series stainless steels are not nearly as gall-prone as the 300-series and they can be hardened so 440C bearings can have an excellent service life.

That said, there is no need for stainless steel bearings in bicycle service as they balls run in a relatively enclosed and grease filled environment. I agree that grease and labor are better investments.

The best bearings are Superleggero. I believe Sheldon Brown sells them: http://sheldonbrown.com/lirpa.html at $2.95 each its a steel! :) They are the best because they are lighter, like all bike parts! You have to read it to understand why they are so good! haha

:eek: :roflmao2: :roflmao2: :eek:

:thumb:

Check here! Bag of 100 of most sizes for less than $5.00

http://www1.mscdirect.com/CGI/NNSRIT...r=1746%50mode=

Good prices there. Very nice. The 1/4" is a true bargain!

These folks have good prices, too. But their 1/4" can't match MSC -

http://www.biketoolsetc.com/index.cg...l%20bearing&s=

In fact I'll be needing some quite soon. At present I am overhauling a 1982 Campagnolo Record bottom-bracket. Nice loose bb's. So smooth...