Ceramic bearings have been a topic of debate for a long time. Some people say that they are nothing but a scam, while others swear by them. After doing some research, we found the truth about ceramic bearings and where on your bikes you might want to use them. In this article, we will discuss the truth about the super expensive ceramic bearings as well as the benefits and disadvantages. We will also provide an in-depth review to help you decide if this is something worth investing in or not!
What are ceramic bearings?
Ceramic bearings are made of ceramic balls instead of steel ball bearings covered with a thin layer of oil. Ceramic is an inorganic compound made by heating Silicon Nitride (SiN4), Alumina Oxide (Al2O3), Zirconia Oxide (ZrO2), or Silicon Carbide (SiC) to extremely high temperatures until they fuse into one solid unit.
Most, if not all ceramic bearings for bicycles use steel inner and outer races because ceramic races are brittle and bicycle bearings have to bear heavy loads from the riders and road imperfections. So, using ceramic races doesn’t make much sense on bicycle bearings.
Ceramic bearings are usually three times more expensive than standard steel bearing sets (sometimes more). The claim is that they have very low friction and save you big watts. Whether that is true or not, we will find out in the next section.
The other main difference between ceramic and steel bearings is the clearance or space between the ball and its housing. Ceramic bearings have a smaller clearance because ceramic doesn’t expand as much as steel when it gets hot.
The advantage of ceramic (hybrid) bearings vs steel
In the right use application, ceramic bearings have many advantages over steel bearings such as:
- Ceramic ball bearings are rounder and smoother than steel, so the coefficient of friction is lower
- Increased bearing life compared to ceramic bearings with ceramic races
- Require less lubricants compared to steel bearings (lower frictions)
- Ceramic balls don’t expand as much as steel when hot
- No cold welding
- Ceramic balls are lighter than steel
Now, these all may sound good, however…
Do ceramic bearings work for bicycles?
The short answer is no.
Ceramic bearings have been around for decades and were used by NASA on space shuttles. They are in use on high-end vehicles like Ferraris, Bugatti Veyron, and Porsche Carrera GT.
This doesn’t mean that ceramic bearings on your bicycle are better than steel bearings.
The majority watt saving of ceramic bearings doesn’t come from the ceramic itself, but the bearing seal, cage, lubrication, and manufacturing quality. While it is true that ceramic balls are smoother and have lower coefficient of frictions, the difference is not significant enough for the low RPM use in bicycles. The thermal property of ceramic balls is also irrelevant because of it.
If you’re looking for weight reduction, ceramic bearings do not offer good dollar value per gram saving. We’re talking about less than 5 grams of difference per bearing.
When and where do ceramic bearings make sense?
In a non-bicycle context, ceramic bearings (not hybrids) do offer many advantages such as:
- Less friction: Ceramics are extremely hard and smooth. They have a lower coefficient of friction than steel balls, which means they will roll smoother for longer periods.
- Longevity: Because ceramics don’t expand or contract in heat like steel bearings do, they last longer under harsh conditions (heat/cold). They are also harder than steel, so they don’t deform as easily. This is not the case for ceramic hybrids as they have steel races which are not as hard and will get worn out by the balls.
- Reliability: Ceramics are less porous than steel and therefore, do not corrode as quickly or easily. They also resist rusting better due to their chemical composition (which differs from stainless steel).
It makes sense to use ceramic bearings in places where the above advantages are needed. In the chemical and medical industry, for example, ceramic bearings are highly useful because they do not corrode like steel and no lubrications equals fewer contaminants. The aerospace industry is another area where the use of ceramic bearings makes sense because they don’t cold weld.
In the bicycle context, however, all the advantages are irrelevant.
It gets worse because hybrid bearings (ceramic balls inside steel races) are not as durable and reliable as steel or full ceramic bearings in the long term. Hybrid bearings’ ceramic balls have higher hardness than their races, which means over time the balls will wear out the races at a rate faster than even the much cheaper pure steel bearings.
How many watts can you save using ceramic bearings?
Not much at all.
Theoretically, one ceramic bearing can save you about 0.15-0.20 watts compared to a standard OEM steel bearing. But again, the majority of the watt saving does not come from the smoothness and hardness of ceramic balls as claimed by online sellers and distributors; It comes from better seal/cage design that have lower friction.
If you compare a hybrid ceramic bearing to a comparable steel bearing with a similar quality, the difference is less than that.
Moreover, ceramic bearings wear out faster than steel bearings, so after a few thousand kilometers your ceramic bearings will have more friction and be less efficient.
So, are ceramic bearings worth it?
For most people, no. Unless you really care about the miniscule watt saving and you can afford to buy replacements before they wear out.
On CeramicSpeed’s website, they claim that using their products in your hubs, pulley wheels, and bottom bracket (which cost over $1500 in total) will only save you 6-9 watts. Considering it’s their own claim, the number they came out with is probably the best-case lab test scenario and the real-world number is going to be much lower than that.
Look at these graphs, taken directly from CeramicSpeed’s website:
The difference between the most efficient bearing (theirs, for obvious reason) vs the worst one (sleeve bushing, not even ball bearing) on pulley wheels is only 1.337 watts. And the difference between ceramic and steel ball bearings is 0.013 watts.
On a side note, funny how the bars difference in height look so massive when it’s only 0.5 watt.
For pros, ceramic bearings might be worth it. Pro cyclists do use ceramic bearings because any watt saving, no matter how small, will surely give an advantage in the highest level of competition. Also, they are getting paid to use them while the rest of us have to pay to use them.
But why do ceramic bearings feel smoother?
While some people can’t feel any difference. Some people swear that ceramic bearings do make each pedal stroke feel a little bit smoother.
Do they really? Well, maybe, if you are sensitive enough to feel the difference. Or if you replaced an old steel bearing with a new ceramic bearing, you might be able to tell.
However, that probably has little to do with ceramic.
The actual reason why ceramic bottom brackets feel nicer is that they generally use lower friction seals and low viscosity oils which contribute the most to the watts saving at the cost of long-term durability. So, new ceramic BB bearings will feel lighter to spin than steel BB bearings because steel bearings use thicker grease.
After a few hundred kilometers, though, you won’t be able to tell the difference.
The other reason is probably something like the placebo effect. If you spend lots of money on ceramic bearings, your mind subconsciously tells you to expect them to feel better, otherwise it means admitting that you just spend lots of money for nothing. Before you buy a ceramic bearing, try a friend’s bike who uses ceramic bearing and compare it with someone else’s who uses steel bearing (just make sure the bike setup is comparable, other than the bearings themselves).