After all this, you can’t blame me for being slightly hesitant when ceramic bearing technology started to crop up in bicycles. If I am being absolutely honest, I thought that ceramic bearings were a total hoax until recently. Before we get into that, though, I think a crash course in bearing basics is in high order.
There is a plethora of articles that discuss all angles of bearing technology as it pertains to cycling all over the internet. So I will do my best to stick to the basics. These two articles from Zipp do a great job of explaining some of the merits of “good bearing design” so I will save my breath by not delving into radial contact vs. angular contact. Bearings are classified in two different ways: Grade, and ABEC rating. ABEC or Annular Bearing Engineering Committee ratings are used to classify the roundness of a ball bearing. A high ABEC rating means that the bearing has a lower eccentricity than a lower ABEC rating. These ratings are ideal for applications that require a smooth rolling bearing at extremely high RPMs. I’m talking like 30,000 RPMs. So unless you do your fast cadence drills at 30,000 RPMs, any rating of ABEC 5 or higher (9 is the highest) will do just fine. Cyclists often put too much emphasis on an ABEC rating. The real rating that effects cyclists is a bearing’s grade. Grade measures three things: surface integrity, size, and sphericity. What you need to know: the lower grade is better. A grade 2 or 3 bearing is ideal. A bearing’s manufacturing tolerances, however, are not the only cause of drag. Bearing seals and lubrication viscosity are major players in causing bearing drag.
So why does all this matter? How does ceramic technology come into play? Relax, I am about to tell you.
Si3N4 (Silicone Nitride) Ceramic bearings are not only lighter than standard steel bearings, but they are also stronger. Zipp claims a 30% weight savings and a 40% gain in overall strength. I haven’t seen the studies to confirm this, but Zipp is a technology driven company. They have loads of engineers doing complicated math problems with lots of numbers and decimals that I trust know more than I do about these kinds of things. I think it is safe to say though, that ceramic is a stronger lighter bearing material than steel. The savings in weight is negligible at best, but the gains in strength have major ramifications when it comes to rolling resistance. A stronger ball means that you can use a thinner (more viscous) lubrication and seals that cause less drag. This directly translates into a faster rolling bearing. Though the reduction in drag is mostly caused by low drag seals and high viscosity lubrication, these are only options because the ceramic ball is less susceptible to wear. If you were to use the same seals and lube with a steel ball, the life of the bearing would be drastically reduced—maybe even destroyed in a single ride.
Both steel and ceramic bearings can be manufactured to the same grade and rating, but that does not mean that they will perform the same over time. Besides the performance gains I already mentioned, a ceramic bearing will hold its grade longer. As a steel bearing wears, it will come out of round and small chips and imperfections will form on the surface on the bearing—both causing rolling resistance. Ceramic bearings are much harder than steel, meaning they will hold their form and resist chips and cracks for much longer than steel.
Like steel bearings, however, ceramic bearings are not all created equal. Actually, grade 25 bearings or higher don’t even have the right to vote in most states. When making a choice of bearings make sure you pay specific attention to grade, type of seal, and both viscosity and fill rate of the grease.
I know you are all asking, (silently in your head, I hope—because otherwise you would be talking to a computer…and everyone would be whispering about you) “All this technical jargon is well and good, but what good does all this do me out on the road? How much difference does it actually make?” I asked myself similar questions—it being a part of my inquisitive nature. Where’s the beef, so to speak? Well, the beef is in the pudding…or something like that. All the technical information and scientific studies in the world wouldn’t mean a thing unless it makes us enjoy riding our bikes more, right? That is why we love cycling—for the riding.
Here in the shop we recently had an opportunity to install ceramic hub bearings and derailleur pulleys on Thomas Brown’s Cyfac. Thomas is one of our favorite customers, so when he asked us to hook his bike up with some ceramic upgrades in addition to a full overhaul, we were really excited to dive into the project.
Believe it or not, derailleur pulleys are one of the leading causes of drag among drivetrains. A faster rolling set of derailleur pulleys will improve shifting, as well as greatly reduce drivetrain resistance. We replaced Tom’s old Campy pulleys (which are better than most standard pulleys to begin with), with Enduro Zero pulleys.
Shiney Enduro Zero Pulleys-The derailleur before the overhaul
---Disassembled----------Cleaned and ready to go!-
With the installation of the pulleys the drivetrain spun with very little resistance. With a spin of the pedal, the crank would rotate at least 3 full rotations. (spin your crank arms on your bike….they probably don’t go around 3 times). Before the conversion, Tom’s cranks spun about 361.7 degrees around. I measured it.
We also replaced old campy steel bearings and retainers with shiny black Si3N4 ceramic bearings with a synthetic retainer.
-Campy Ceramic Bearings---The hub before the conversion--
Notice that Campy recommends using only a light oil to lubricate the bearings.
-New bearings and oil-----------The finished product.----------
This allows for a drastic reduction in rolling resistance. I was thoroughly impressed when I took this bike out for a test ride. The Cyfac Nerv is a great riding bike to begin with, but I was totally struck at how smooth the bike rode after the conversion. It spun up smoothly and was very responsive. I immediately looked into ordering ceramics for my Caad9, but then I remembered that I’m completely broke. Oh well.
So what can we take from all of this?
Ceramic technology really does make a difference out on the road, but are a more expensive than standard steel bearings. So you have to ask yourself how much you are willing to spend for the top level of performance. We all have to decide between bike upgrades or say…donuts. For me the choice is obvious: donuts.
Thanks for reading. See you at the shop.
PS. I would love to hear any comments or suggestions for topics for the mechanical posts on this blog. This blog is yours just as much as it is mine—except for the fact that I write the posts. But I really do want to know what topics you are interested in discussing. Don’t hesitate to email me at email@example.com. Or leave your comments and suggestions in the “comments” section. Rocket science, right?
Additional Links and Pictures:
Ceramic Tech Information
Zipp Si3N4 Technology
F1 Ceramics explains grade and ABEC ratings
Campagnolo Delta Brakes