There was a time when a 10-42 cassette on a mountain bike looked ridiculous. Then, seemingly overnight, it looked normal. And then their 50, 51, and 52-tooth successors quickly looked normal, too. To the point where a 36-tooth mountain bike cassette now looks anemic by comparison.

And such is the case after having installed the Kogel Kolossos pulley cage. All else now appears small and weak in comparison. And, in reality, they are.

Kogel Kolossos install notes & actual weights

closeup of the kogel kolossus oversized ceramic bearing pulley

The Kolossos oversized derailleur pulley uses a machined cage with trussed reinforcements to create an overly stiff, overly large replacement for the stock derailleur cage on your road bike.

They offer versions for Shimano, Campagnolo, and SRAM’s latest top-level road rear derailleurs, as well as mountain bike versions. I tested mine on a Dura-Ace Di2 R9100 rear derailleur that has seen countless miles.

closeup of the kogel kolossus oversized ceramic bearing pulley shown from behind

The back cage plate is smooth and flat.

Where the stock Dura-Ace (and Ultegra) cage uses 11 teeth for both upper and lower pulleys, Kogel ups that to 12 and 19, respectively…and spins them both on ceramic bearings.

Installation is easy, but does require disassembly of the stock cage and will void your warranty. Kogel provides easy-to-follow instructions, but here’s a quick look at it:

disassembled dura-ace rear derailleur

The first step is removing the stock cage, which is just a few bolts, including the retention pin that you’ll need to reinstall with the Kolossos. You’ll also remove the Stop Pin and re-install onto the Kolossos in one of two positions, depending on whether you had a short- or medium-cage derailleur.

And you’ll reuse the spring and its seal, which simply slides off once you have it all disassembled.

kogel kolossus rear derailleur pulley cage spring and parts disassembled

What’s nice about Kogel’s design is they give you three different slots to notch the retention spring into. They advise starting in the middle position to test performance, but the others provide either higher spring return force for offroad/gravel riding or lighter force for smooth roads. The former will help with chain retention on bumpy stuff, the latter makes shifts easier.

kogel kolossus oversize derailleur pulley closeup

Two stop pin positions ensure the pulley cage can’t retract too far when the wheel is off or the chain drops off the chainrings.

All told, the process took maybe 20 minutes, including minor adjustments to the B-screw and limit screws to fine tune placement on the bike.

actual weight of kogel colossus os pulley upgrade on a rear derailleur shown on the scale

The Kolossos added 38g to my derailleur. Kogel admits their cage might be a bit heavier than some other aftermarket oversize pulley options. They also say it’s stiffer, and I’ll explain why that’s a good thing in a minute.

How does it affect chain length?

chain length and derailleur position comparison after installing an oversize pulley cage

The original pulley cage on the left, Kolossos on the right, both in the big-big gear combo.

Kogel says that you may need to add a couple of links, but I didn’t have to. Above, the before and after with the chain in the big chainring and largest cog.

While I wouldn’t normally ride in the big-big combo, it’s always good to make sure the system can handle it. This might look like it’s at its limit, but it felt fine and shifted in and out of the big cogs smoothly and quietly.

chain length and derailleur position comparison after installing an oversize pulley cage

And here’s a comparison of pulley cage positions in the smallest and largest cogs when shifted into the small ring. With both extremes tested and working just fine, there was no need to add links to my chain.

Kogel Kolossos ride review

riding action photo for the kogel kolossus oversized ceramic bearing pulley review

The big question is, does this $400 upgrade improve performance?

Yes, but it’s definitely subtle. It’s hard to argue with bearings that spin freely when you’re holding it next to something that will get but a few revolutions for the same effort.

So, yes, these clearly have less drag, and thus reduce drag while pedaling.

riding action photo for the kogel kolossus oversized ceramic bearing pulley review

Shimano’s Dura-Ace Di2 group’s shifting performance leaves little to be desired. But, a stiffer pulley cage that smooths the chain’s path through it will (or should, anyway) make things just a bit crisper and smoother.

But it’s subtle.

riding action photo for the kogel kolossus oversized ceramic bearing pulley review

What’s less subtle is how much quieter it is. This, combined with a clean and properly lubed chain (with something like the CeramicSpeed UFO Drip, as used here), will effectively reduce your drivetrain noise to nothing. It’s impressive.

Also, I love the looks of it. I’m kinda having a hard time imagining the bike without the oversized addition now. It certainly stands out and has become quite the conversation starter, too…so there’s that, if you’re into that. (And if you’re really into that, they also make it in Gold and Red)

closeup of the kogel kolossus oversized ceramic bearing pulley

Is it worth it? Depends. There are certainly areas where $400 will make a bigger impact on performance. But if you’re down to the final few marginal gains to be had, the Kogel Kolossos OS derailleur pulley cage delivers smoother, quieter performance with crisp shifting and sharp aesthetics.


  1. Daniel on

    aluminum pulley wheels are never quiet!. This is the madness of todays third party manufacturers who think polymer is bad… because Shimano/Sram is using it. So lets make things worse and use aluminum that radiates the sound. They simply can’t afford the injection mold so they turn them from metal.

    I used their pulleys and also many others made of alu. When I finally moved back to polymer I suddenly found what quiet actually means.

    Not to mention Shimano has way taller teeth profiles on top pulley than all those alu ones. This is what makes the shifting good or bad.

  2. hoyhoy on

    I ran Kogel instagram pulley wheels for less than a year and the bearings failed. I tried to warranty replace them and they refused to honor their own warranty. I’d stay far, far away from anything Kogel.

  3. angry mechanic on

    Have you ever wondered why shimano placed lower pulley slightly at an angle? No it’s not you that bent the cage, it’s originally made like that. It’s to accommodate the chain angle when on bigger cogs of the cassette to reduce the noise and provide better shifting.

    this one is totally straight and supposedly very stiff leavening no room for error. I love those little companies who think they are smarter….not.

  4. solarider on

    I do wonder when/if the big 3 will simply make this their standard, thus relegating these aftermarket oversized pulleys irrelevant. If they really are that good, surely fitting one as standard wouldn’t add anything like the aftermarket cost to an OEM part and provide the Big 3 with a relatively cheap win for a component that is pretty much as good as it can otherwise get now, short of ditching derailleurs altogether as a means of shifting gears.

    • Crash Bandicoot on

      From what I can tell these oversized pulleys do little to nothing in terms of actual performance improvements. According to pink bike this saves 2.5 watts, of course that is assuming perfect frame tolerances (lol), I’d wager that the excess aerodynamic length and potential additional chain weight likely negates the minuscule watt savings. A wise professional triathlete who was sponsored by a company that makes products like this once told me, “if you are good enough for these things to make a difference then you’re not paying for them anyways”. My guess is the market for products like this is as tiny as their watt savings so it’s not worth it for the majors to make their derailleur a worse to market it them. There’s also an element of people that will always want to modify or hot rod stuff from third party companies.

  5. Mathias on

    It’s too expensive for what it does. You better spend those money on good set of hubs. Efficiency of bicycle depends more on hubs, because hubs carry load and hub spin tires. Prefferably Dura-Ace or XTR or Record (hubs).


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