Other than changing the stock 30-tooth chainring to a 32-tooth option, my S-Works Stumpjumper Evo is the only bike I’ve ever had where I didn’t feel obligated to switch out all kinds of vital components to create a bike with my desired performance characteristics (which, for a bike with a price tag over $11k would hopefully be the case). Weather permitting, I ride that bike four to six times a week, and also use it for enduro races.
Equipped with SRAM’s top-shelf XX1 Eagle AXS wireless drivetrain, admittedly I wasn’t too excited about disassembling the derailleur to put on an aftermarket cage with claimed performance benefits when I had no discernable performance issues with the stock derailleur. Obviously, I don’t manufacture drivetrains in my spare time (rather, I tend to destroy them). I’ve built dozens of race bikes from scratch, but one thing I haven’t ever done was take apart a rear derailleur and monkey with the inner workings.
So, once I emotionally came to terms with the fact I did indeed need to disassemble a perfectly fine working derailleur to install the Kolossos, I literally rehearsed the very simple process over and over. I’ve replaced broken plastic pulleys and straightened bent hangers, which are relatively mindless procedures, but foolishly I was concerned that if I made a mistake winding the derailleur spring back in place with the Kogel cage installed I’d end up with a handful of XX1 Eagle AXS bits and Kogel-equipped non-functioning derailleur. I sort of felt like I was disassembling the internals of a Rolex, just to put on an aftermarket watch band that claimed to help me tell the time a bit better. Regardless, the installation process was extremely simple, and I quickly felt foolish for being so concerned about terminally messing up one of the most expensive derailleurs in the mountain bike game.
Any rider worth their weight in chamois butter knows it’s recommended to change all drivetrain bits at once, rather than only putting on a new chain, etc. The reason being, the longer the chain, cassette, and chainring are all working together, they more they tend to wear into each other and eventually will only play nice with those exact components they’ve grown to know so well.
Since I’d changed the pulleys (with significantly more pronounced teeth than on the stock plastic XX1 pulleys) on the derailleur I felt it was best to then install a new chain, cassette, and chainring as well. Due to the supply chain issues, I waited several months for an XX1 chain and cassette, and a new 32-tooth oval chainring to become available. Eventually, I just gave up and decided to give the worn drivetrain a go with the new Kolossos cage. The only modification I did make was to add three links to the chain, because the Kolossos uses 14 and 18-tooth pulleys, which are larger than the stock 12 and 14-tooth ones I removed. I already run a chain that’s likely a smidge on the short side, because when descending in the smallest cog on a 1x 12-speed drivetrain there’s a lot of chain leftover that can flap and slap around when charging down rough terrain. On one piece of instructional material from Kogel it suggested installing a new chain with the Kolossos cage. Whereas on another I read a new chain was not necessary, however adding a few links may be. Regardless, I had no choice other than to add a few links to my old chain, and thankfully after months of riding that setup I’ve had zero issues of any kind.
Not only does the Kogel Kolossos system look killer when installed on the bike, but I instantly noticed a reduction in drivetrain noise over the stock plastic pulleys. Instead of the chain rattling back and forth on the stock pulleys, the chain sits deeper in the longer pulley teeth and therefore makes for a more quiet ride, presumably improving chain retention as well. When it comes to shifting, the SRAM’s AXS wireless setups are already pretty darn precise. Yet, shifting with Kolossos cage felt more crisp in crucial gear-change moments, like downshifting for a sudden steep uphill section of trail, or upshifting and popping through the gears under full-power sprint.
When it comes to the claim of increased wattage, it would be disingenuous if I said I noticed anything significant in that area. In fact, simply meticulously cleaning one’s current drivetrain, and servicing their bottom bracket and wheel bearings, would almost certainly reduce the energy loss over a given distance. Road racers in a peloton or time trialists who hold one particular body position over a significant distance would be much more likely to notice increased drivetrain drag than on an often grime-filled mountain bike drivetrain. However, in the world of elite mountain bike racing, fractions of a second accumulate and ultimately matter. Whether in a 3-minute downhill race, over multiple stages of an enduro event, or during a fast-paced World Cup XCO cross-country event, performance advantages add up and ceramic bearings make perfect sense in those applications. For me, the benefits to looks and shifting crispness are good enough reasons to have the Kogel system, and it’s nice to know that I’m having to work that little bit less hard to summit those climbs.
It is worth mentioning that installing an aftermarket third-party product, like Kogel’s cage and pulleys, will likely void the derailleur manufacturer’s warranty. I asked SRAM if installing the Kolossos cage would void the warranty on the roughly $750 (original MSRP) XX1 Eagle AXS derailleur, and it appears so. Here is their response: “We do not test the use of third-party parts as spare parts nor do we support the use of these parts. Because we do not test third-party compatibility, installing one of these parts may cause unforeseen damage to the component. The official language in our warranty policy is that the warranty does not apply when the product has been modified.” So, proceed with fitting the Kolossos system at your own risk if you can foresee any need to pull the warranty card on your derailleur.
The Wolf’s Last Word
Like most bike nerds, I am proudly in tune with my bike setups. Each ride, I set the exact same tire pressure with a digital gauge. And I regularly service my fork and shock and refer to the notes I make so I can return to the exact performance characteristics after the service. Despite not really wanting to disassemble my derailleur, I’m probably the type of mountain biker Kogel’s Kolossos cage was designed for. You certainly don’t have to be a World Cup competitor to appreciate the reliability, subtle performance benefits, and increased bling factor Kogel’s Kolossos cage provides, although adding a $475 derailleur cage and pulleys won’t be for everyone.
Price: $474.99 (stock color) / $524.99 (custom)