The Pros and Cons of Ceramic Bearings
What is a Ceramic Bearing?
While regular bearings are made from stainless steel, ceramic bearings are made from ceramic silicon nitride (Si2N4). Rolling resistance is the key trump card promoted by ceramic bearing fans. Because ceramic bearings are rounder with a smoother surface and more uniform size, friction is reduced and that can contribute to a less energy required to turn the cranks or spin the wheels. A ceramic bearing is also harder than steel bearings (up to 30%), which improves durability, and they also don’t rust so less maintenance should be required.
Most sealed ceramic bearings are actually hybrid ceramic bearings, which combine a steel race with ceramic ball bearings. Full ceramic bearings use ceramic races, which can be lighter and provide the lowest friction, but come at a durability cost. Unsealed ceramic bearings can be used to upgrade components that don’t use cartridge type bearings, like cup and cone hubs.
Ceramic Bearing Pros
Longevity of a well-built high-quality ceramic bearing, in many cases, can be up to 10 times longer than commonly used stock bearings. The 'rule of thumb', as we like to call it when built well, and of high-quality materials, a ceramic bearing should always be able to outlast and outperform a steel bearing.
The second advantage of ceramic bearings over stock steel bearings is their performance under load in reducing drag. Performance cyclists are performance driven and all data shows that the best performing bearings for reducing drag are ceramic bearings.
That, in theory, should mean less energy is required to turn the wheels or cranks. Add the lower weight and improved durability, and why wouldn’t you run ceramic bearings? But are all ceramic bearings the same? Of course not, CeramicSpeed is keen to point out that not all ceramic bearings are made equal, and it tells us that a ceramic bearing built poorly with low-quality materials will deliver very poor longevity.
Ceramic Bearing Cons
Not Made for Cycling
We have looked at ceramic bearings in the past and talked them over with our bearing suppliers,” explains Hope’s Alan Weatherill. They do run with less friction, which offers a significant advantage in industrial applications running at 20,000 rpm. A tiny percentage reduction in friction here can equate to a worthwhile power saving, but when you're only turning at 300 rpm, as you do on a bicycle a small percentage increase in efficiency will make a negligible change to your power output. Certainly not worth the significant increase in cost.
Leading industry wheel dynamics expert and CEO of Edco Wheels , Paul Lew, backs this up and reckons it makes ceramic bearings a poor choice for hubs and headsets, also adding that they offer no weight savings and are only beneficial in environments where high rpm (revolutions per minute) are required.
For bottom bracket applications, the maximum sustained rpm may be 130. For wheel hub applications, the maximum rpm may be 500 – 600 revolutions per kilometer (depends on wheel/tyre diameter). The maximum rpm values in cycling are far below the typical ideal rating for ceramic bearings which is 10,000 rpm+.
It’s clear that Alan and Paul agree that the factors that make a ceramic bearing well-suited to industrial and medical equipment applications, and high-altitude operating drone motors (Paul does a lot of work designing drones) where the rpm is high, the load is low and the operating conditions are clean, are factors that mean they’re not suited to cycling.
Bikes require grease (not good for ceramic bearings)
Ceramic bearings are beneficial in environments not requiring grease lubrication. But a bicycle is expected to cope with a vast range of conditions, rain and dirt, and where maintenance schedules may be less than optimal, and the last thing you want is to ride bearings without grease. It’s this requirement to cope with the conditions common to cyclists that offset the promised lower rolling resistance of a ceramic bearing, according to Paul Lew.
The rolling resistance of a ceramic bearing compared to an ABEC 3, 5 or 7 steel ball bearing is offset by the resistance of the grease. In order for a ceramic ball bearing to out-perform a steel ball bearing, grease is not an option. Does this mean I should run my ceramic ball bearings dry or with light oil? Yes, but you won’t like the result in an environment where the bearings can become contaminated. If you run your bearings dry they will feel gritty and rough.
Hope’s Alan Weatherill concurs with Paul Lew’s conclusion that ceramic bearings are not suited to the demands of cycling and says their suitability to industrial machinery doesn’t necessarily provide the performance benefit for cyclists that many people and companies claim they do.
Ceramic Ball Bearings are too Hard
Another issue with using them on bicycles is their hardness. While this again is an advantage in many industrial applications, it's a major drawback on bikes. The shocks from hitting potholes and other road blemishes impact the hard ceramic balls into the softer steel races commonly used. This dent in the race is then felt when the bearing is rotated, giving you rough bearings.
Then there is the fact that Ceramic bearings aren’t cheap. CeramicSpeed’s BSA Road external bottom bracket for threaded frames costs £298. A Shimano Dura-Ace 9000 bottom bracket cost £39.99, much less if you shop around. A CeramicSpeed bearing upgrade kit for Campagnolo and Fulcrum wheels will set you back £120, and Zipp charges £194 for a CeramicSpeed bearing kit for its wheels. That makes upgrading to ceramic bearings a serious investment, fine for a professional cycling team, less so for a privateer racer.
The premium for ceramic bearings is high then, and their advantages, while looking promising in an ideal world, appear to stack up much less in the demanding environment that a bicycle is expected to perform and survive in. So should you choose ceramic bearings? We’ll let Paul Lew have the last word.
Although the re-selling markup/ margin for ceramic bearings is significant for manufacturers such as Reynolds, and they could represent a profit-center for the brand, we choose not to offer them because they don’t improve performance, and they represent a consumer cost that we can’t justify, and that’s contrary to our value system.
Hawk Racing Bearings
It is our opinion that the cons of a ceramic bearing significantly out weigh the pros of a ceramic bearing. Which is why we set out to make the #1 alloy bearing on the market.
Our bearings will give you friction loss that is comparable to ceramic bearings without all of the cons that are associated with them.
Head over to our website to see all the Hawk Racing alloy Bearings we have to offer!!