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KCNC Ceramic Derailleur Pulleys

Tue, 01/12/2010 - 11:03pm by Andy Shen

I received some KCNC ceramic pulleys from Fairwheel Bikes, a Tucson bike shop known for its eclectic inventory of specialty parts. Aside from being anodized in pretty colors, these pulleys promise better shifting thanks to a bit of lateral float, as well as less drag from its ceramic bearings.

In terms of float, these pulleys fall between Shimano (lots) and Sram (none). My Sram drivetrain did seem a tiny bit quieter with KCNC pulleys installed, but the difference was so tiny that it could have been my imagination.

The real interesting claimed benefit of these pulleys is reduced drag. Fairwheel's site claims that derailleur pulleys are the best place for a bearing upgrade, since they're the fastest spinning bearings on the bike. If you pedal at 100 rpm, your pulleys are spinning at 481 rpm's in the big ring, and 355 rpm's in the little ring (53/39). The faster the bearings spin, the more watts they suck up, so the logic goes. I have my doubts about this, since derailleur pulleys see far less radial load than wheel and BB bearings, and load also increases bearing drag. But since I have no way of testing this, let's just press on and see if these pulleys do decrease drag compared to stock pulleys.

There's two ways to reduce pulley drag: upgrade the bearings, and use a larger, slower spinning lower pulley (you can't put a bigger one in the upper position). A quick spin test immediately raised doubts as to the quality of KCNC's bearings – Sram's pulleys, also with ceramic bearings, had much less drag. Perhaps this is a good time to harken back to what Josh Poertner of Zipp said about ceramic bearings (cheap ceramic bearings are made to withstand heat, and don't necessarily spin faster), as well as the fact that Rich Sawiris of only recommends Ceramic Speed bearings (Ceramic Speed pulleys go for $140 on Fairwheel's site, KCNC, $35). KCNC's bearings may be ceramic, but they sure don't seem fast.

Next I tested the pulleys on the rollers, with a Quarq Cinqo crank and a PowerTap wheel. Since the Quarq is upstream of the pulleys and the PowerTap downstream, drivetrain drag should show up in the difference between the two power readings. I rode with a constant cadence using a metronome, and I did runs in both the big and little rings. Runs were done on Sram, Shimano, KCNC 11-11, and KCNC 11-12 pullleys.

Sadly, the differences involved were all well within the claimed margins of error of the Powertap and the Quarq. The only conclusion I might draw are that the Sram pulleys seemed 4 or 5 watts more efficient. But to reiterate, this was all within the margins of error for the two power meters.

Lastly, I tested one more theory from Fairwheel's Emiliano Jordan. He thinks that for the same gear inches, you're better off riding in the little ring than the big ring. The thinking is that when you're in the big ring, the rear derailleur is more stretched out, and that extra spring tension puts a radial load on the pulleys which increases drag. I ran the same pulleys in the big ring and small ring, pedaling at 100 rpm in the small ring and 74 rpm in the big ring so that the pulleys spun at the same speed, and got almost identical numbers.

So what's the moral of our story? First of all, things that make sense logically may not pay off in terms of real world benefits. Secondly, all ceramic bearings aren't created equal, but lesser bearings in your derailleur pulleys will probably only cost you a watt or two.  Based on my somewhat inconclusive tests, I'd have to say that derailleur pulleys aren't the best bang for the buck for a bearing upgrade. But there's a silver lining. One of my Sram pulleys split, causing my chain to occasionally pop off and lodge between the pulley and the cage. I happily swapped out the composite pulleys for the KCNC aluminum pulleys.

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By: Stephen Barner
Tue, 07/22/2014 - 6:35am

The comments about KCNC knocking off designs led me to look up Patent 192122, as labeled on the pulleys. The US patent with yhis number was issued June 19, 1877 for an "Improvement in machines for crozing, chamfering, and equalizing staves", presumably barrel staves. There is an international patent that includes that number, but it is for fiber optic connctions. I guess the patent claim is merely a graphical element.

On a more serious note, this type of jockey wheel is not going to be long-lived under adverse conditions, regardless of the quality of the ceramic bearings. There simply isn't enough aluminum on the outside. Under grit conditions, these pulleys will likely wear through to the lightening cutouts before the bearings fail.

The drag increase may very well be due to the bearing seals. A small drop of very light oil to the seals may recuce this significantly, at the expense of collecting grit. Any drag tests should be done after subjecting the bearings to a reasonable break in period.

Test Method
By: Lucas Tubie
Wed, 05/11/2011 - 10:38pm

The best way to test the drag of the pulleys is to use device called an active dynamometer. It consists of a calibrated electromagnetic hysterisis brake that applies constant torque. This is configured to measure simulated road loading and measure the drag on the pulley at loads (rpm) measured in torque units (dynes). You can also use the brake itself like a rheometer to turn at a constant speed and measure the resistance force of the bearings (using very small weights in the sub-gram zone). The resistance force will only be relative to the samples (an empirical test). Either way, you won't get stronger by farting around in the test lab. Ride!

It's definitely because the
By: Diego Cage
Fri, 04/22/2011 - 11:44pm

It's definitely because the pulleys are adorable.

It's definitely because the
By: Danato Tubie
Fri, 04/22/2011 - 11:43pm

It's definitely because the pulleys are adorable.

Nice one!!
By: property management company mn
Fri, 04/22/2011 - 11:09pm

The pulleys look newly painted. It is shining and sparkling. I wonder why people collect a pulley and don’t use it for important things; maybe they are just collecting it because it looks adorable.

Wow - the haters
By: Recco Chainline
Thu, 02/17/2011 - 1:57pm

Love the number of people with "well I would have done it this way..." or "Your wrong as...". Additionally, the hateful stuff... While can be funny, I am quite sure you would not say that majority of it in person. Anonymity creates some serious courage. Enjoyed the write-up.

Are you supposed to lube
By: Anthony Supple
Sun, 07/18/2010 - 2:50am

The old style shimano ceramic bushing pulley?

Plagiaristic KCNC
By: Alessandro Brazeon
Thu, 05/20/2010 - 11:17pm

KCNC machine shop in the isolated boonies in Taiwan's Shoushwei Township in Changhua District. They're very low-end in Principles and Values, they prey upon idealistic Westerners to submit designs, product lines for mfg., then hijack the customer's design idea for their own promotion with the excuse we're not interested in mfg for you.

They make many claims about lightweight stems, pulleys, cranks, copycat Zero Gravity brakes, etc...resulting with failed components that leave its Retailers feeling betrayed. KCNC's classic excuse for a Component's Catastrophic Failure is "We accidentally shipped you a prototype" or "It's busted from your mechanic's error". The excuses are meant to waive liability and distract from the root cause- inadequate testing / no testing, non-genuine authorship of application (as it was stolen from a Western Designer with manufacturing endeavors).

I feel bad for Fairwheel's Mr. Jordan and other entrepeneuring Retailers, as they purchase directly from KCNC (who sells at the Taipei Bike Show) and travel afar looking for the coolest, shiniest gadgets to make a decent dollar without knowing they're headed for a "dollar descent". That's why you occasionally see snippets of KCNC at grassroot websites.

The only English Speaker at KCNC is Mr. Jackie. Otherwise they try and exploit Western English Instructors in Taiwan with a penchant for cycling and idealistic values. Their many components have machine marks, stress raisers as disguises and an excuse for design.

KCNC is not represented by a bonafide US Distributor for all the reasons that industry insiders know of ; bad failure rates, copycat complaints, piracy, no testing, excuses for waiving proper component protocal, no US liability insurance.

I'm glad this grassroots website tested the KCNC Ceramic pulleys and came to an objective "aint all that". Unlike other websites with "review by looks", this website truly gives objective results- 2 Thumbs Up.

P.S- KCNC failures:

Cracked Scandium BB, Cracked Al7075 & 6061 Road & Mtn Stems, Catastrophic Failed Al 7075 Alloy Cassettes with Ti, Broken Seatposts.

Information gathered from Personal Victimization, Ex-Retailers, End-Users.

Jig is up
By: West Coast Reader
Thu, 01/21/2010 - 8:28pm

I like the jig idea, but you still need something to measure the drag the pulley is causing. So something to spin the jig at a measured rate and pressure (torque) and then calculate the difference? Something like that.

Solving the pulley mystery is like solving a jigsaw puzzle
By: Guillaume Crank
Thu, 01/21/2010 - 5:40pm

From the previous post you can get the jig but then you still need the saw. You can't go "I solved it, I solved it!" and then when people ask you for the solution and you only have a jig and no saw, they would go "You have not saw!" and then you'll be the laughing stock of the scientific testing of pulleys world. I suggest you ask Lorenzo Rivnut for a saw.

new test protocol is needed.
By: Lorenzo Rivnut
Thu, 01/21/2010 - 4:39pm

I propose you create a jig to test the pulleys. You could use the remains of an old derailleur. Mount the pulley in the cage, use a torque wrench to get the preload the same during your test. The take a chain and loop it over the pulley. Add a 10lb weight to one side of the chain and a 5lb weight to the other. Raise the 10lb weight 3ft off the ground and do several timed drops to see how long it takes to reach the ground. Average out the number and see what you get. Then repeat with the other pulley/s.

new balls bearing frutis
By: Taddeo Bottle
Wed, 01/20/2010 - 12:13am

Gripes! Twice! The Sky is falling on the Shack! The season is already long...

You can't imagine? Good thing
By: Loic Ferrule
Tue, 01/19/2010 - 9:15am

You can't imagine? Good thing the writer quantified it then. Thanks for your unverified musings though.

real world
By: Alexander Saddlebag
Tue, 01/19/2010 - 12:44am

I cannot imagine that any of this makes a damn bit of difference in the real world other than as a negative i.e. worn/dirty or otherwise compromised bearings might create a little extra drag. but really the only thing that matters on a bike is aerodynamics (somewhat) and the quality of the rider.

As far as I could tell
By: Andy Shen
Mon, 01/18/2010 - 2:15pm

As far as I could tell they're interchangeable.

Thanks for writing up
By: Steve M
Mon, 01/18/2010 - 12:06pm

Hey Andy,

Very cool, thanks for writing up your test results.

Do you think Sram red ceramic pulleys would work well with DA7900 derailleur?

Mark Twain drank Old Crow
By: Remigio Cage
Sun, 01/17/2010 - 12:41pm

Mark Twain drank Old Crow

By: pearl e. gates
Sat, 01/16/2010 - 1:14pm

it's like comparing Basil Hayden and Pappy Van Winkle Bourbon. Both are excellent. By comparison, comparing Old Crow and Pappy Van Winkle, and you will know the difference immediately.

What if?
By: West Coast Reader
Sat, 01/16/2010 - 12:42pm

Well maybe testing some really ratty pulley's would prove disprove your hypothesis? If some pulley's off a $100 bike (new) show the same result then, yes you are right. Comparing top of the line vs supposed top of the line might not show much difference. I'm not saying it will prove the ceramic's are better just that any pulley will be the same.

Now to find some ratty pulley's?

Been working the last couple
By: Andy Shen
Sat, 01/16/2010 - 1:43am

Been working the last couple of days, catching up on some questions.

Spin test wasn't claimed to be accurate, but I think it lent some insight into the quality of the bearings.

Slope measurement for each power meter was not necessary. I was looking at the change in the relative measurements, so as long as they were consistent that was good enough. If I wanted to know the % power lost in the drivetrain, then I'd need to measure the slopes and y-intercepts and have a good grasp of the absolute numbers.

Gearing was the same for all the runs, very obvious factor to control for.

I don't NEED better test equipment. My aim was to test a marketing claim (these pulleys save power) because false advertising bugs me, and I think I did enough to say that claim is dubious at best.

As for 'the final straw', you need to work on your reading comprehension. The point is that these things DON'T help you, and that just because some bearings are ceramic, doesn't mean they're better. The $140 pulleys might really be better, but I doubt they'll help you much either.

spin test is lame
By: Roboto Derailleur
Fri, 01/15/2010 - 3:02pm

What matters is parasitic loss under load, not freely spinning.

As mentioned, the results are within the margin of error. Additionally, you would need to do a measurement of the slope of each powermeter (with a known weight) in order to ensure the meters are correctly reading the proper numbers. Additionally, different f/r gear combinations have differing amounts of drivetrain loss, so you would need to factor that in as well. (Human Power 52 summer 2001, Chester Kyle and Frank Berto, Human Power 50, Spicer (with subsequent analysis in 51 by Walton & Walton)

Eben gets about a million
By: Loic Ferrule
Thu, 01/14/2010 - 2:21pm

Eben gets about a million per, he's that good at blowing Lance.

Re: Sacha Biopace comment
By: Webmaster
Thu, 01/14/2010 - 12:18pm

Ouch! How many extra web hits is a blowjob worth these days?

The final straw
By: Alexis Brakepad
Thu, 01/14/2010 - 10:50am

I'm so excited about this development. For years I've been feeling like my derailleur pulleys have been holding me back, keeping me from making the big jump to Cat 3. This is almost as revolutionary as the internal headset.

By: Gregorio Internal Routing
Wed, 01/13/2010 - 11:43pm


By: West Coast Reader
Wed, 01/13/2010 - 10:11pm

I think "the moral of the story" is you need better test equipment. At least to get the numbers you need or more accurate ones.

I heard the Aluminum pulleys were noisier than those plastic-ish ones? What's the word on that?

I bought some a while back (different brand) and thought they were less draggy (no solid data, of course) and the red bearing cover looked cool (hey at least I admit it)

Bikesnob takes a shot at Andy
By: Lennert Dry Lube
Wed, 01/13/2010 - 6:01pm

"This is called "cabin fever." One day you're compulsively spinning derailleur pulleys, and the next you're talking to a volleyball and roasting and eating your housepets."

Eben had some downtime from
By: Sacha Biopace
Wed, 01/13/2010 - 3:01pm

Eben had some downtime from blowing Lance?

By: mikeweb
Wed, 01/13/2010 - 2:39pm
I feel better
By: Gianni Rear Entry
Wed, 01/13/2010 - 1:39pm

Thanks Andy. Now I have confidence that I am doing the right thing by buying beer instead of cermaic pulleys.

Here's my logic. The pulleys
By: Andy Shen
Wed, 01/13/2010 - 11:35am

Here's my logic. The pulleys are on the lower run of the chain, so it should be independent of power. I kept chain speed constant, used the same gear combo, so the power output was pretty consistent anyway. But the key number is the difference between the two power meters on the same run, so some inconsistency between runs shouldn't matter too much.

I didn't use a torque wrench to make sure each pulley was installed with the same bearing preload, though.

Your last detail - the SRAM
By: Larry Hanger
Wed, 01/13/2010 - 11:30am

Your last detail - the SRAM pulley coming apart -- made me wonder: ss there any difference (quality, durability) between composite/plastic pulleys like the default Shimano D/A, and replacement aluminum ones, all bearings being equal?

not to nitpick, as I know you
By: Aurelien Brakepad
Wed, 01/13/2010 - 10:47am

not to nitpick, as I know you don't claim this is scientific, but the "spin" test you employed is hardly reliable. who is to say that (a) you spun each with equal force, and perhaps more importantly, (b) you held each pulley with equal force?

Perhaps a coast-down test from a given speed (on rollers or a trainer) with the only difference between each run being the pulleys might be more appropriate?

By: Samuel Seatpost
Wed, 01/13/2010 - 10:38am

You may not pick up any watts with new pulleys, but they can significantly increase performance. I just switched out the pulleys on my winter bike with Shimano 105 shifting. I put in something similar to what you are reviewing here except they have steel bearings in a sealed cartridge. It only cost me $35, and it works as well as the Campy Chorus on my race bike.

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