Wish my wheels spun like these :)

[DIMS]

http://www.youtube.com/watch?v=q4Tc1...eature=related

http://www.youtube.com/watch?v=frQzE...eature=related

[bgd73]

be careful about ceramics.
I had a subaru that had yellow bearings..when asking about them, it was some kind of experiment..with ceramic. Absolutely horrifying, I was nearly killed when it shattered in the back end. wheel turned on its own, on an aggressive road.

steel may pretend its slower,more firction..but when push comes to shove with 3000 pounds and all day...the steel is gonna win...and do add some racing grease. no regrets.
for bikes and people on them, great, I do not even like ceramics on brakes or clutch pads...it fails me miserably.

think tractor trailer comparing for your car,more than a bicycle.... and trucks fail the ceramic clutch too...

[Ryland]

ceramic is about as likely to shatter as steel, I've had bicycle ball bearings brake in half, why? because they were not adjusted correctly.
The ceramic that they use is white, it's a simaler chemical makeup as the ceramic knife blades you can buy, same family as man made diamonds.

[RandomFact314]

That is pretty amazing that they keep going and going and going. That would be great for coasting.

[Old Tele man]

...they're using ceramic bearings in jet engines for "both" longivity and low-friction...as well as the usual high-temperature capabily.

...here's GE: http://www.advancedceramics.org/clie...36_3_10_09.pdf

...I know about it via the Allison (Rolls-Royce) YJ102R engine.

[Frank Lee]

LOL on the motorbike!

See the calipers dangling uselessly?

Get the brakes to release so the wheel does that when it's fully assembled and then they'll have something!

I want to convert the ShWing to drums.

Or put drums on it!!!! The back wheels in my Sport Coupe spin like that motorbike wheel- no brake drag and they're running in gear oil. The front wheels on my '59 Bel Air spin like that too; they have ball bearings, drum brakes, and of course are large diameter so the flywheel effect lets 'em go for a loooooong time.

I'd feel better about the bicycle "test" if the rims 'n' tires were identical, and they were spun by electric motor to identical rpms at the start. IMHO adjustment and lube, as well as quality of mfg tolerances could easily have more effect than composition of the balls 'n' races.

[Toby]

Originally Posted by Old Tele man

...ceramic bearings in jet engines for "both" longivity and low-friction

Unfortunately, the applications of a jet engine and auto wheel are not mechanically homologous. A car wheel experiences large shocks transverse to the axis, while a jet engine ideally does not.

I'm not an expert, but I don't think there are any ceramics available at mass-production prices that approach steel's modulus of toughness.

Ceramic bearings are super cool though. Rear derailleurs on bicycles have used small ceramic bearings for years. They are especially nice because they don't require lube and will never squeak.

[Frank Lee]

Originally Posted by Toby

Unfortunately, the applications of a jet engine and auto wheel are not mechanically homologous. A car wheel experiences large shocks transverse to the axis, while a jet engine ideally does not.

I'm not an expert, but I don't think there are any ceramics available at mass-production prices that approach steel's modulus of toughness.

I think the added robustness of roller bearings vs balls when jolted i.e. hit a pothole is why rollers replaced ball bearings even though the balls have the r.r. advantage. SAE says bearing drag is an almost negligible factor anyway...

[Toby]

Yeah, bearing drag is a throwaway term in the large majority of engineering problems. In a biomechanics course I took years ago we learned that for a cyclist, the energy lost to friction in the rider's joints is far greater than that lost to the wheel bearings.

As Frank Lee has pointed out, we still have brake calipers that don't retract. How carmakers can drone on about their amazing technology and commitment to efficiency when this issue has been around for decades is beyond me.

[Frank Lee]

FINALLY lower drag calipers are making their way to market. Why it took 60 years is beyond me.