Found: Berner Bikes’ Carbon Fiber Derailleur Cage Upgrades


Germany’s Berner Bikes makes carbon fiber upgrade parts and accessories, carbon road and ‘cross frames and other bits. These replacement derailleur cages caught our eye despite having been available for a while now.

Available for SRAM Red, Shimano Dura-Ace mechanical and Di2, and Campagnolo Super Record, the carbon fiber cages use oversized 13t and 15t jockey wheels with slick bearings to reduce friction. You can order them as a hop up kit on its own, or as a complete derailleur. You can even send in your own and have them do the conversion for you. They even offer a Ceramic Speed bearing upgrade if you’ve got money burning a hole in your pocket.

The switch adds about 19g to the part, but they say it’s good for almost a six watt savings and that numerous pros are running them in the peloton. The Shimano Dura-Ace part’s shown above, click through for more pics and pricing…


The outer face of the Shimano part above, a converted SRAM Red derailleur below.


Prices range from €269 up to €659 depending on model and whether you’re ordering parts or a complete derailleur.


Dave B - 08/04/14 - 9:47am

Let me see if I understand this. These ADD weight, add cost of $300 to $750 and are claimed to save more watts than a rear derailleur actually consumes, right? P.T. Barnum was too conservative.

gerald t. - 08/04/14 - 10:36am

Wow, thanks for bringing this to our attention bikerumor. How did i ever live without it?

AlanM - 08/04/14 - 10:50am

@gerald t., do you not understand what Bike Rumor is all about? It’s about interesting bikes, parts, etc. Don’t want to read about these, don’t click on it. I skip over all sorts of articles that don’t interest me and read the ones that do. It’s the beauty of the Internet! Then again, I don’t get to be as pissed off all the time as you.

eadm - 08/04/14 - 11:40am

much easier for a chain to get around

Champs - 08/04/14 - 11:50am

Dave: Larger pulleys on bigger bearings ought to roll more smoothly. Snake oil or not, there are riders after marginal gains where they can get them, like riding with Alberto Contador on the Port de Balès. Ahem.

Mick - 08/04/14 - 11:58am

@AlanM – +1…
@Dave B, gerald t…as best I can tell, no one is holding a gun to your head to either click on any links, or to purchase any products you see on BR…

Jock E. Wheel, Esq. - 08/04/14 - 12:59pm

A company publishing misleading numbers doesn’t bother you, as long as they don’t use force?

Mario - 08/04/14 - 1:38pm

Why would a Carbon Cage be heavier? Is it larger?

MarkV - 08/04/14 - 1:45pm

Cool idea and nice potential benefit, but the $’s to benefit is really hard to swallow. Who made this for him…..Swiss Watchmakers?

John - 08/04/14 - 5:22pm

Make longer cages for DA Di2. Lots of us Freds & steep mountain climbers want bigger cassettes on our fancy Di2.

mark - 08/04/14 - 11:46pm

For 99.% of the cycling world, something like this simple is not necessary. very cool, very expensive, but the cost vs gains are so far out there. The concept is simple. By making the pulley larger, the chain can turn the pulley easier by overcoming the friction in the bearing much easier. This is the exact opposite idea that makes Kreitler small-drum rollers so hard to spin. The bearings are the same but increasing or decreasing the diameter by which you are trying to spin them makes them easier or harder to spin. the carbon cage has no benefit over the stock aluminum one unless they just needed to make something out of carbon.

Derek - 08/05/14 - 2:53am

@John You can use the long cage off of an Ultegra FD on your Di2 setup.

Chris - 08/05/14 - 7:42am

Aerospace engineer here:

The pulleys are going around slower. Power is torque times rotational velocity, so slower pulleys consume less energy.

Larger diameter pulleys require less force to overcome the torque of the bearing. Power is also force multiplied by time, so less force over the same time is less energy.

Finally the chain’s link will swivel over a smaller angle joining and leaving a bigger pulley. Less chain articulation will mean lower frictional losses and less energy.

ian spivack - 08/05/14 - 12:55pm

Here is a link to purchase the study on the benefits of the Berner cage:

Geoffrey - 08/09/14 - 3:12pm

@Chris, great explanation. I was waiting for someone to put this in engineers laymans terms.

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