Do oversized derailleur pulleys really help? Part 2

posted by Ard Kessels
January 31, 2017

In part one of this post we analyzed oversized pulley systems and their effect on friction and shifting. Today we will look at their use in mountain bike setups and what you can expect from Kogel Bearings.

Increasing chain length

Sram introduced their new Eagle mountain bike group set last summer and it sure is another game changer. I remember when 50 teeth was reserved for chain rings, now we use it as a rear cog. The 50 tooth cog was introduced to increase the range of the drive train. Sram developed the XX1 group a few years earlier, which caused mountain bikers world wide to take the front derailleurs off their bikes. (Have a look at this viral video to see some new uses for your fd). The 46 tooth large cog on the XX1 did not offer a large enough range for everyday riders, forcing them to choose between pushing their bike uphill or getting dropped on fast downhills. Problems were solved by introducing a massive 50T cog as a twelfth gear.

  • The Scott-Odlo team with Jenny Rissveds and Nino Schurter rode the Eagle setup to double Olympic gold. Photo courtesy of

This large cog requires a longer chain in order to make smooth shifts. Instead of increasing the length of the derailleur cage, Sram increased the lower jockey wheel size in order to prevent the cage to run close to the ground and be susceptible to rock strikes. My wild guess is that they left the top pulley untouched at 12 teeth to increase shifting accuracy.

Good looks

Being a self declared bike snob, I need to address this issue. Let's face it: bigger pulleys just look badass. Any chance I get to make people look at my bike and open a conversation with 'Whooaa, dude....' I will jump at the occasion. Bigger is better. 

What about Kogel Bearings oversized pulley wheels?

Kogel Bearings judges products by their performance in the #terrainlab, we will bring performance benefits as long as they do not stand in the way of everyday use. We love reducing friction, but not to the point where it affects shifting or increases chances of ripping off your derailleur. You will not see a Kogel Bearings derailleur rebuild kit being sold anywhere soon. 

Increasing chain length: makes total sense, we follow Sram's guidance and actually use a 14 tooth lower pulley on our Sram Eagle ceramic derailleur pulley set

Good looks: We are always ready for a bit of experimenting on our own bikes: Our sram XX1 compatible 12 tooth pulley set can fit on Shimano mountain bike derailleurs by changing a dust cover. It actually seems to improve shifting accuracy due to the narrow-wide tooth profile. You will have to accept my word as circumstantial evidence for that though.


  • A 14 tooth pulley on a short cage derailleur? Probably not the best idea. Just don't judge me for trying, OK?

We have also managed to install the 12 tooth wheels on some short cage road derailleurs, but it's a hit and miss: Ultegra mechanical fits fine, Dura Ace Di2 runs fine, but Dura Ace mechanical seems to have some interference with the cage. Once it fits, it sure will turn some heads at your next ride, but please give me a ring before clicking the order button.