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Is there a real difference between riding on ceramic bearings and riding on stainless steel?

How would you measure it? Does it require it to be every bearing in the drive train, or will each set of bearings replaced improve performance?

Does anyone have real world experience with them to relate?

Edit:

I don't know if it matters on the bike, but I saw this today. If this is an indication of the difference in the level of friction resistance ceramic offers, then I'm in.

In the video:

The left pulley shown is Shimano DuraAce, the middle one is Campagnolo Record 11 speed. All three pulleys are fixed to 5Nm of torque at the axle bolt. And all 3 three have at least 1mm of play at the pivot, so there is no extra tension on the bearings compared to normal install in a derailleur. There is a difference in movement of about 18 seconds of spin in the video. It's crazy.

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I'd only sorta heard of them. This page extols some of their (supposed) virtues: performancebearing.com . –  Daniel R Hicks Aug 7 '11 at 11:59
    
But at prices of roughly $2.50/ball, ya gotta really want them. –  Daniel R Hicks Aug 7 '11 at 12:04
    
I'm looking at www.ceramicspeed.com sets. They claim significant durability improvements, and the on display setup certainly seems to back up the claims of improvements in terms of friction. There are folks that say it is as much as a 5% decrease in power output, while maintaining the same speed and heartrate (as close as they can be measured.) That implies more speed for the same effort, or less effort for the same speed. I'm interested, even at the obscene pricing, but only if I will notice the difference. –  zenbike Aug 7 '11 at 12:12
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Yeah, if they really can reduce rolling resistance enough to notice that would be big. But keep in mind that air resistance is by far the larger factor at any "road" speed. If you use them, I would guess that you'd want to do the bearings carrying the most weight first -- probably rear wheel, then front, then bottom bracket. –  Daniel R Hicks Aug 7 '11 at 12:35
    
I wonder if Lance Armstrong used them. 5% is not to be ignored if it is true. –  Moab Aug 7 '11 at 22:59

6 Answers 6

up vote 15 down vote accepted

The short answer to your first question is "the power savings from using ceramic bearings compared to good steel bearings is almost zero." The short answer to your second question is "yes, it is possible to measure the difference but it's not easy." The longer answer, and the support for the shorter answers is below.

First, however, it depends a little on whether you're talking wheel bearings, or bottom bracket bearings, or both. If you're interested in measuring the difference, the way you measure differs for the two. BB bearing drag would show up in differences in drivetrain efficiency, while hub bearings would show up as a component of rolling resistance. The difference, of course, is that drivetrain losses only occur when you're pedaling, not while you're coasting, while rolling losses occur as long as you're rolling, whether pedaling or not.

You can measure differences in no-load hub bearing drag by holding the wheel up in the air with a fork, using a home-made speed sensor jury-rigged with a reed switch connected to a digital voice recorder. You spin the wheel up, then record and calculate the difference in timing "clicks" as the wheel decelerates. Swap bearings, lather, rinse, repeat.

However, this would be in a no-load setting and you might think differences in bearing drag might be amplified in load-bearing situations. If so, you'd have to test that way. You could do it in the lab but it's also possible to do yourself, in the field, with the jury-rigged speed sensor.

First some background. The rolling component of drag is typically measured by the coefficient of rolling resistance, Crr (the coefficient of aero drag is Cd, which is usually multiplied by the front surface area, A, and described by the combined term CdA). Crr can have a speed-dependent component but at cycling speeds this is negligible so we can assume Crr is constant. If so, the power demanded for moving a bike and rider at a given speed is pretty well known and understood: rather than go through it all here, I'll point to a (um, brilliant) method that allows you to estimate CdA and Crr which can be found here.

Now, if you do all of this, you'll find that for a typical bike, the total overall Crr from all sources (tires, tubes, hub bearings, and typical "smooth" road surface) of around .005. The Crr for really good tires on that same surface might be .0045; for really lousy tires the Crr might be .006; and for a really rough surface the Crr might go as high as .01. And, some context if you look at the power equation linked to above, you see that Crr scales exactly like gradient in its effect on power so when the Crr is .01, the effect on power is exactly like climbing a 1% grade. Likewise, an increase in Crr of .001, due either to a different tire or to putative bearing differences, is just like climbing a grade 0.1% steeper.

Here's one more fact, also derivable from the link above: a rule of thumb is that at 25 mph on a flat hard surface, a cyclist in good aero position needs around 250 watts (an exceptional aero position is achievable with under 200 watts). At 25mph, a difference in Crr of about .0005 is roughly equivalent to a difference in power of 5 watts. That is, a difference between a good tire and a very good tire is worth about 5 watts at 25 mph.

If you have done any field-testing of bicycle drag you'll realize that 5 watts difference in rolling resistance is pretty noticeable. Riders report that the difference between using ceramic and steel hub bearings is not noticeable.

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Welcome to Bicycles! Nice answer! –  freiheit Aug 22 '11 at 2:09

I have just read your article on ceramic bearings and am forced to give you an unprofessional view point. Firstly i am an 80 year old bike rider who rides weekends with a younger group of 6o year old riders. If you are still with me , my riding consists of between 30 to 40 kilom each ride at a speed of between 25ks and 35ks . I find recitals about ceramics nearly always are about the cost and no advantage.The reality is that a person of my age keeps up with a fitter group[. While there may be a slight speed advantage what counts is that i am fitter at the end of the ride than i would be with steel bearings. People decry ceramics being used by young fit cyclist who in the same breath would argue that a few grams saved may.make...a lot of difference. I have two TREK roadbikes with ceramics and a CANNONDALE road bike with steelbearings and changing roadbikes on riding days shows a decided difference. Your comments almost suggest it would be nice if we could all drive a Mercedes if they were not so dear so a Ford will do. *

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Welcome to Bicycles Stack Exchange! This is really a comment, not an answer. While this type of post is welcomed and expected in a traditional online forum, it's not in line with our goals as a Q/A site. Please see the Tour for an overview of how this and other Stack Exchange sites work. You may then want to edit your post to more clearly answer the question asked. –  Gary.Ray Aug 29 at 13:39

The material that the bearings are made of is only one piece of the whole mechanical package. I've worked on bikes in the shop that had ceramic BB's and all sorts of steel. From a material point of view, ceramic has the possibility to be better, but as others have noted, you pay a large premium...and often they may not be the best anyway.

Think of it this way, oak makes a better table then pine. But pine is easier to work with and the resulting table might be smoother and put together better than the oak one...and cheaper at that. Likewise, there are steel BB's, hubs, etc. that are better than some of the ceramic bearing counterparts. I have my favorite and it's a decent priced steel (Hawk Racing), I have yet to see anything that is better on a bike that I've worked on.

Sidenote: Videos like the one shown should be taken with the grain of salt...it's marketing and the demo has been set up for a particular purpose. Talk with the guys at the LBS and get opinions from both sides of the counter (the mechanics and the customers).

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Since the current answers are very road specific, I'll give my take on it for the disciplines I know.

Downhilling can benefit from them because they deform less under load, so in theory last longer. But in practice BBs and hub bearings in this discipline tend to fail from corrosion brought on by failed seals, and although ceramic bearings won't rust - the race will. The lower shock load isn't an issue due to long travel suspension.

For trials it really depends on how much of weight-weeny/rich you are. Ceramic bearings weigh far less than steel ones, so there's an instant benefit there. But, ceramic bearings are much less resistant to shock load so they will shatter, and because trials bike's are rigid, this will happen quickly.

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I don't have the source at hand, but from what I've read, converting your wheel bearings to ceramic will net you something like a 1 W savings at racing speeds, thanks to reduced mechanical losses. A ceramic bottom bracket would result in less improvement.

Considering the rider is putting out 200+ W at racing speed, the savings are clearly minor. Additional savings may accrue from the much lighter wallet the rider is carrying.

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I have ridden ceramic BB bearings. This is my one and only experience. They seemed to take a couple rides to break-in which definitely seemed odd. One of my training partners noticed the same thing, but in his case, it was after 90 minutes that the bearings seemed to spin freely.

I rode them for just shy of a year, which is approximately the same usage I get out of standard bearings. Based on the insane price and insignificant difference, I opted to go back to stainless.

The riding partner, I mentioned earlier, is on his second set after going back to stainless. If funds permit, I am open to trying again. It was not a bad experience in anyway. Another buddy has swapped all bearings including derailleur pulley bearings and swears by it!!

That's all I got!

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Can you expand on the "insignificant difference"? Maybe there are no more details to add, but could you detect any change in the riding/coasting/noise etc experience? –  Mac Aug 8 '11 at 23:56
    
Please do expand. I'm looking for specific details... I have to justify this as a purchase to my accountant... oops, my wife. :) –  zenbike Aug 14 '11 at 5:34
    
Since my only experience is using ceramic bearings is in my bottom bracket, coasting is not a factor. In terms of noise, there was no difference, meaning there was no noise. Now riding, this is perhaps the arena where there was an ever so slight smoother feel and maybe pushing the pedals required the most minute degree of less effort. For me the difference was only felt when the pedals were under pressure...either attacking or climbing. –  GuyZee Aug 18 '11 at 15:11

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