Hybrid or Full Ceramic Bearings

Factual Questions
1

as a senior citizen indoor roller skater, i am interested in skates that need less effort to use. every one agrees that ceramic bearings are the best bearings (less friction) for roller skating indoors. my limited research raised more questions. the hybrid bearings, ones with ceramic balls and metal races, are the most recommended. they come with zirconium oxide or silicon nitride balls. the full ceramic bearings with different combinations of zirconium oxide or silicon nitride; balls, races and cages, is where the confusion comes in.

from my viewing of full ceramic bearings on the internet, the zirconium oxide balls are usually matched with silicon nitride races and can be ordered with or without cages (usually ptfe).

is zirconium oxide harder than silicon nitride? wouldn’t you want the balls and races to be the same material, such as the chrome steel balls and chrome steel races on most bearings?

is there an advantage to mixing the different ceramics or is it just a financial thing. although, ceramic bearings are not inexpensive by a long shot.

i’ve read that mr. adams has a ceramics engineering background. what combination on non-combination of zirconium nitride or silicon oxide ceramics (balls and races) would he recommend for the least rolling resistance bearings on a pair of quad indoor roller skate (limited shock force)?

i did experience a noticeable ease in skating on hybrid ceramic bearings over my high abec steel bearings. would i get a noticeable ease in skating with full ceramic bearings over my hybrid ceramic bearings?

2

But ANY senior citizen roller skater who refers to Cecil as “Mr. Adams” is damn fine by me!

Welcome to the boards!..stick around and chat. Want some coffee?

3

And check out your keyboard for a defective SHIFT key while you’re waiting for the experts…

4

the shift key started touch typing work stoppages in my early sixties. it refused arbitration in my early seventies. i’m not sure what it’s next move will be but i’ve started practicing ‘instant messaging’ typing just in case. otherwise, i m ok.:slight_smile:

i’d love to have a cup of coffee but the keyboard union calls wildcat strikes when i enjoy a little caffeine. oh for the good old days.:slight_smile:

5

zirconium oxide Hardness Kg/mm^2 1300
silicon nitride Hardness Kg/mm^2 1580

However, zirconium oxide has a higher fracture toughness than silicon nitride: 13 vs 6.1 MPa•m^1/2.

Naturally, these numbers depend on how the two materials are actually manufactred.

6

thanks. it looks like silicon nitride races, and balls would be a good combination ($39 each). at roller skating speeds, it doesn’t look like there is any major difference in performance between any of the combinations.

since you need 16 bearings for quad skates, it’s not a minor purchase especially in the context of roller skating. one reason why i sought outside help. thanks again for the info. i hope to have a set (installment payments) by the winter skate season.

old boys and their expensive toys.:slight_smile:

7

i found a detailed set of charts on the different types of bearings;

http://www.ceramiccycling.com/Tech%20info.html

looks like no extreme jumping on ceramic bearings.:slight_smile:

maybe fracture toughness is why the most popular full hybrids are a combination of zirconium oxide races and silicon nitride balls?

8

I’ve done a bit of reading on ceramic and hybrid bearings due to an interest in turbocharger and bicycle applications. They DO offer benefits, but beware of exaggerated claims and fad-based marketing.

You really want the races to be a bit softer than the rolling elements. (balls in this case, but the same applies to roller bearings)

Even with the highest attainable precision, the races are not as perfect as the balls. Balls can be made round by processes that are largely self correcting…essentially an optimization of the same process that rounds and polishes river rocks. If the races are softer, then the balls can wear or deform the races into near perfection. If the races are equally hard, then the balls get damaged some by the races, which causes wear in “good” parts of the race, which wears other balls, and so the bearing quickly wears out. Additionally, either the balls, the races, or both MUST deform some, or the force is applied to zero area, which gives infinite pressure, which will break anything. Thus at least one of the materials needs to be able to deform without fracturing, and then spring back. Steel is pretty good at this, and that is why steel race bearings survive impact overloads better than ceramic races.

The more the race deforms under load, however, the greater the bearing drag. Thus there will always be a trade-off between performance and robustness.

The drag reduction due to ceramic balls alone is modest if the ball and race dimensions are maintained. This does improve load capacity though, so hybrid bearings can be “downsized” (smaller and/or fewer balls) to reduce drag. In addition the super hard balls tend to “iron out” or heal minor damage to the races, so they tend to maintain low drag and ultimately last much longer than steel balled bearings. * Thus even if the contrast between NEW bearings is modest, the performance gap will widen over time.

It’s your money, spend it as you will, but if it were my money, I’d go for the hybrids as offering lots of bang for the buck.
*I’ve seen one white paper where a single steel ball was replaced by a ceramic ball, and resulted in greatly enhanced bearing life. The conclusion was that the single hard ball was able to heal race defects, sparing the steel balls the wear that would otherwise result.