Found: Berner Bikes’ Carbon Fiber Derailleur Cage Upgrades

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

much easier for a chain to get around

@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…

Spartacus uses one.

http://www.cyclingnews.com/features/photos/pro-bike-fabian-cancellaras-radioshack-leopard-trek-domane-6-series/259059

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

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.

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.

http://www.friction-facts.com/test-results/individual-reports/oversized-pulley-test

According to Friction Facts, the actual savings is about 1.8 watts over the Dura Ace 9000 11/11. The savings comes from 3 sources: Lower friction bearings, larger, slower spinning cogs, and, quite importantly, the spring tension applied to the chain is lower.

The price is 380 EUR. For people spending $8K on their bikes, this seems like a completely reasonable expense. If 10 similar enhancements were available, it would cost about 4K to add 18 watts, which is a serious advantage. You’d probably get better performance if you bought a $4K bike and did the 18 watts of enhancements.