Bicycle Bottom Brackets with Ceramic Bearings
would be so easy if we all had an unlimited bank account or a
corporate sponsor to buy all the newest in bicycle part technology,
but reality sets in and choices must be made. What I want to know
is if the hype about ceramic ball bearings used in bottom brackets,
hubs and headsets is really worth looking into or is this just
another over priced gadget that is great to talk about over a
Ceramics are relatively new to the bicycle industry. With the
exception of a few companies like FSA, cranksets and other bike
parts have typically used "steel" bearing. But ceramics
have been around in the industrial arena for a number of years
for cutting tools, turbines and even in satellites.
Companies like SKF spends millions of dollars on bearing research
and have even sponsored the Ferrrari racing team since 1947 to
give themselves a platform to test their new technologies. Did
you know that today's Ferrari F1 racers contain over 150 SKF bearings
and seals? And you better believe that if just one-half horspower
can be gained through reduced bearing friction, then racers will
be having serious discussion about bearing technology. Anyways
I'm getting a little sidetracked but here's a list of why a serious
racer might want to consider ceramic bearings like those used
in some of the FSA
So what's the big deal?
35% less Thermal Expansion:
Think of putting a coke in the freezer. You have to allow for
its expansion or you'll blow the tin. Steel bearings are like
the tin of pop. Ceramics on the other hand change size significantly
less then steel with a given shift in temperature, thus raceways,
rings and seals from a typical bearing can be made to much greater
tolerances. They can even be fabricated with a smoother finish
so vibration goes down and stability goes up.
50% less Conductivity:
Ceramics are electrically NON-conductive, and chemically inert,
thus do not suffer from oxidation and the rust that degrades the
surface of a traditional steel ball bearing. They suffer less
heat damage since they don't heat up as easily. This helps to
maintain the spherical geometry of the ball bearings and significantly
reduces your repair time.
60% less Weight:
Since silicon nitride is only about 40% of the weight of bearing
steel the savings are obvious. Think about tying a heavy rock
to the end of a rope. Its hard to get in motion and hard to stop.
The lighter the rock the easier it is.
The issue of bearing weight is the same story. The heavier they
are the more effort it takes to get them rolling and stopping.
Thus ceramic bearings, with less then half the weight, and thus
less rotating mass, will be much more responsive in acceleration
and deceleration, with much less effort.
50% Higher Modulus of Elasticity:
that's just a fancy way to test how easy it is to deform something.
Ceramic has a 50% higher modulus of elasticity, so it takes a
lot of work to alter its original shape. That gives you a much
longer life expectancy in a hard wear zone like a bicycle's bottom
Steel on steel has a nasty habit of welding itself together, that's
why you use anti-seize on some fittings. In a bearing the lubricate
helps to prevent this but when bearings sit over the winter this
can happen. Ceramic is NOT able to weld itself to steel. Steel
and Ceramic are incompatible in that respect so cold welding is
another difficulty you can avoid with ceramic ball bearings.
So what does this mean to a company like FSA that has chosen
to make some of its bike parts with ceramic bearing? Studies by
a number of cycling magazines, FSA and even bearing companies
like SKF have repeatedly shown extended life expectancy.
Research suggests that FSA Bottom brackets equipped with ceramic
bearings have a 5-10 times longer life. Industrial literature
might suggest ceramics add 3-5 times the life expectancy. Either
way we know they'll be there longer than their carbon steel cousin.
Equally exciting, in tests with Olympic and professional racers
and in controlled lab tests with wheels, ceramic bearings repeatedly
show significantly less friction, making for faster speeds, acceleration
and deceleration with less force.
So whats not to like? Only the price. Ceramic Bearings are easy
to justify with longer life, less vibration, more speed but at
maybe 5 times the price of traditional bearings the questions
still remains as to whether you can justify the added cost?
|| Silicon Nitride
Hardness (Vickers Hardness Scale)
| 1580 kg/mm2
|Maximum Use Temperature
|| 1500 C
Bicycle Cranksets Components:
Bottom brackets, cranks & chainrings