This from ZIPP, who makes (very expensive) ceramic bearing
wheelsets. Very interesting, and little of the blatant sales pitch
> The use of ceramic bearing systems in cycling is starting to
> accelerate since the introduction of own ZIPP Z3 wheel set two
> years ago and now with the adoption ceramic bearings by Campagnolo
> I believe we will see an inevitable increase in the use of this
> technology. Judging from the notes and phone calls I receive, there
> is quite a lot of both excitement and confusion out there so this
> is a great opportunity. I will try to answer all your questions,
> but please excuse me if I tend to go on too long: I love this stuff
> and I tend to get carried away.
> I believe it was the writer Robert Heinlein who said something
> along the lines of: "Any technology sufficiently advanced is
> indistinguishable from magic." Ceramic bearing systems aren't quite
> magic, but the technology behind them seems to be getting closer
> all the time.
> I am going to talk about ceramic bearings, bearings in general and
> ZIPP bearings in particular as these are the bearings I am most
> familiar with. Other manufacturers such as Campagnolo will have
> faced similar challenges in adopting ceramic technology and will
> have addressed them in ways best suited their own needs.
> When speaking of ceramic bearings, we are really speaking of
> ceramic balls replacing the more common steel balls in the bearing
> assembly or system. Ceramic bearings do offer dramatic potential
> for significant performance advantages, but the key word is
> potential. Optimal performance is a result of an entire bearing
> system rather than as a result of the ceramic balls themselves.
> What the ceramic balls do by their physical properties is raise the
> bar of what is possible to achieve in the entire system.
> When you start talking about any material, you have to remember
> that there are steel battleships, bridges, "tin" cans and my
> favorite toy, the slinky, all made of steel. In other words, each
> material has a range of properties and it's not the magic material,
> it's what you do with it and how you apply the material properties
> to a particular design solution.
> Modern bearings, any bearing ceramic or otherwise, are really
> pretty amazing technological objects. Steel ball bearings used in
> cycling have tolerances now measured in millionths of an inch. In
> top quality hubs, steel bearings typically will have a tolerance of
> between 50 and 60 millionths of an inch between the balls of a 12
> or 15 ball set. This is not easy to do, but by pushing the
> manufacturing envelope further (and spending a lot time and
> effort), steel ball bearings can achieve a precision of 10
> millionths of an inch total variance per matched set of 15 balls.
> Of course to take advantage of this precision in the ball
> manufacturing, the other parts of the complete assembly must also
> receive similar attention. This attention to detail results in
> improved performance across a broad range of parameters, but the
> basic material properties become the limiting factor. Being the
> performance fanatics (and that's a nice way of saying technology
> geeks) we are here at ZIPP, all our hubs using steel balls are
> using ZIPP designed and custom manufactured bearings sets that
> achieve less than 10 millionths of an inch total variance in
> roundness and size in a matched set. A similar attention of detail
> is applied to the remaining parts of the bearing assembly.
> Now in talking about the above it's time to mention a key part of
> manufacturing: The more time, effort, and precision you insist on,
> the greater the cost. It's pretty much a rule you cannot get
> around. The cost, by the way, increases at an ever accelerating
> rate with each level of precision achieved. By adopting new
> technology and materials (Ceramics!) new options become available.
> Dramatically greater precision and performance can be achieved and,
> of course, the cost also accelerates along its ever increasing
> path. That's the answer to why the price differential exists
> between ceramic and steel bearings.
> Ceramics have been around for several years, but it is the new and
> rapidly developing new manufacturing technology that allows the
> dramatic increases in precision that were unthinkable until
> recently. They are used in numerous industrial, military and
> aerospace applications where long life, high speed, heat, pressure
> and low rolling resistance are required. As with anything, a range
> of quality is possible...but it is the manufacturing technology at
> the highest level that breaking new ground and offering
> unprecedented performance potential.
> How much benefit is possible from adopting this new technology?
> According to reports from real world testing done by ZIPP sponsored
> Team CSC an average reduction in wattage of three to four percent
> under our standard bearing systems, already the tightest standard
> within the industry can be expected. For an average trained cyclist
> developing 250 watts, that's a savings of approximately 10 watts.
> At any level of competition, that is significant. The key is every
> part of the bearing system has seen marked improvements in
> precision resulting an a total benefit greater than the sum of its
> parts. Similar to current math theory, at some point numbers reach
> a point where the rules just don't hold true any more.
> Anecdotally, one our ZIPP representatives recently became a world
> record holder on the track. After numerous attempts and misses at
> the record by a few hundredths of a second, he broke the record
> after switching to the ceramic bearings. He has since lowered that
> record again using the same set up, but in several tries without
> the ceramic bearings has been unable to ever match his original
> record breaking attempt. Of course this was not a scientific test,
> but try to tell him the bearings don't make a difference! Matched
> sets of ceramic balls used in ZIPP bearings exhibit tolerances of
> LESS then one-millionth of an inch total variance in both size and
> roundness with a corresponding increase in surface smoothness. This
> is near the technological limit of measurement and worlds better
> than any steel bearing of any rating or type. These bearings are
> currently exclusive to ZIPP and NASA.
> Ceramic balls of the highest quality are made of pure silicon
> nitride. (Earlier ceramic bearings of any type, possibly familiar
> to skaters or skateboarders, were often merely coated steel balls
> inserted into standard non-specific races and offer no comparison
> to the current state of technology.) The critical issues of
> manufacture are purity of materials, chemistry and particle size
> control, ability of the pre-manufactured material to flow easily,
> packing density, uniform compaction, micro-structural development,
> geometry, surface quality and finish.
> As mentioned earlier, ceramic silicon nitride balls exhibit much
> greater hardness than steel balls resulting in at least 10 times
> greater ball life due to the ability to hold the surface finish
> longer. (Later I will mention cryogenic treatment of the steel
> races. This is required to take advantage of this durability and
> prevent the hardness of the ceramic ball from destroying the race.)
> The ball has dramatically smoother surface properties than the best
> steel ball resulting in less friction between the balls and bearing
> race surfaces. Thermal properties are also dramatically improved
> over steel balls resulting in less heat build up at high speeds. To
> achieve the final surface finish, the balls are floated on a
> magnetic field and polished with plasma stream. They are rated to a
> spin rate of 300,000 rpm versus a spin rate of 33,000 for our steel
> All the other parts of the bearing system and of hub design are
> directed at optimizing the potential of our bearing technology,
> both ceramic and steel.
> The custom steel bearing races are designed and manufactured
> specifically for the loads and requirements of a cycling
> application. The races are cryogenically treated at minus 300
> degrees Fahrenheit to harden and align the crystalline structure of
> the material. The races are then polished to a surface smoothness
> 30-percent greater than an Abec 9 rating, the highest international
> standard rating level. Each bearing assembly also includes a thermo-
> plastic based waffle shaped seal that encloses and locates each
> ball to its optimal location in the race. Friction is further
> reduced by this system as individual balls are kept at their
> optimal location at all times. Lubrication is provided via a
> depleted barium hydro-flex lubricant ($650 per kilogram and used in
> ZIPP bearings!) that is also a product of the space program. The
> lubricant is actively hydro-phobic, meaning it repels water at a
> molecular level. The lubricant is also thermally stable and
> exhibits the same properties at -200 degrees as it does at over
> 2000. Most importantly, it exhibits the lowest friction coefficient
> of any lubricant available. Designed to match the bearing
> performance with modifications adapted to current use, the
> lubricant is rated to spin rates of 300,000 rpm and an expected
> life equal to that of the bearing.
> As a final word, properly designed ceramic bearing systems do in
> our opinion increase performance and will become more common,
> perhaps the future standard. Certainly at the top levels of the
> sport the difference is significant enough to change the out come
> of races all things being equal among similarly gifted athletes.
> For the time being, however, the cost of such technology, even the
> availability of the materials themselves remains a barrier to wide
> application of such systems. Manufacturers like ZIPP and now
> Campagnolo (others to follow) will continue to push this direction,
> but ultimately, it is the individual rider who has to decide if the
> current state of the art is of value to them. In the auto racing
> industry there is an old saying: "Speed costs money; how fast do
> you want to go?"
> Bill Vance
> National Sales Manager and Factory Guy
> ZIPP Speed Weaponry
http://www.velonews.com/tech/report/articles/5327.0.html (Near middle of page) -- Richard Risemberg http://www.bicyclefixation.com http://www.newcolonist.com http://www.rickrise.com