AbsoluteBlack 40-tooth cog for converting to wide range 1x10 cassette

The OneUp 42t cog got quite a bit of attention, and seems to be working out pretty well for Zach after a few tweaks to the rear derailleur. But, AbsoluteBlack founder Marcin thinks he’s got a better solution.

In development for a couple months now, his 40-tooth cog works the same way as OneUp’s: You remove one of the middle cogs to make room for a larger one at the top. The most superficial difference is that it uses two less teeth, which he says eliminates the need to tweak the B-tension screw. In theory, this means the expanded gear range comes with no major adjustments outside of the cassette.

There’s more to it than that…

AbsoluteBlack 40-tooth cog for converting to wide range 1x10 cassette

The tooth profiles are heavily shaped to make shifting crisp and fast. Sets of four up- and six down-shift teeth run around the cog, alternating to provide large swaths of shifting sections that should grab or release the chain on demand.

AbsoluteBlack 40-tooth cog for converting to wide range 1x10 cassette

Marcin says there are two other features that set his design apart. First, it’s about 7g heavier (~77g target weight), but those extra grams are used to make the splines very stiff, which should mean solid shifting and driving. Second, the splines that contact the freehub body maximize the surface contact area, which should reduce the chance of the cog digging into the freehub body, particularly alloy ones. OneUp’s also address this by using wide splines, the main difference here is the height of the holes is lower, so the cog is resting on the top of the freehub’s grooves, too. Time will tell if that makes an appreciable difference – we’re hoping to have one in for testing soon.

He’s shooting for an end of January release. Pricing TBD.


  1. The returns are getting smaller and smaller- all so that the B-tension screw doesn’t need to be adjusted? A 40t cog gives you only a third of the range that an XX1 cassette adds and and 2/3 of what OneUp provides:
    11-36: 327% (standard 1×10 range)
    11-40: 364% (Absolute Black)
    11-42: 382% (OneUp)
    10-42: 420% (XX1)

    And for the inevitable “why not take off the 11t?” comment, the answer is that you would end up with virtually the same range as a stock 11-36 (333%).

  2. By “tweak” the B-tension screw, do you mean stretch it out half an inch or so? Because most standard derailleurs simply don’t have that much range, no matter how much B-tension you add. My opening sarcasm aside, even adding a longer screw won’t fix that; at some point the derailleur rotates too far away from the tab, and the screw won’t engage any longer. These set-ups may give you more range, but they’re sure not going to deliver the perfect shifting XX1 promises.

  3. Oh the negativity lol.

    I’d prefer 40 teeth rather than 42 for a 10 speed block because the jump from 36-42 is just too big, 40 teeth is a good compromise. XX1 may well be great but it has a great price tag too, until the big companies bring out an affordable, wide range 1 x 10 set up this will fill a gap in the market very nicely.

    I’ll be ordering one if the price is right.

  4. What am I not getting here? Why not save up some $ and buy some XX1 or XO1. Chances are you can run your existing crank with a new chainring ($75 from Wolf Tooth works great). All you need is the derailleur, shifter, chain, and cassette. Buy the stuff on sale and you can probably get it all for $600 or $700. Chances are this cog and a new chain will run about $150. I just don’t get the math. Combine that with selling your old stuff for a couple hundred $$ and there you go. Is everyone trying to tell me they can’t save up $500? Come on. Why use these half measures? I guess as a stop gap while saving up?

  5. Save money for a $$$$$$$ derailleur? If you ride where we do a 2 broken year is good news! It is great if you can afford it. Most looking at this can not afford it-what ever reason I bet. In the mountains of WV-we need lower gears,not our 11t. Funny,the guys who brag about their big ring are not as fast as the 1x guys with a 30t here. I hope they do a 38t as well. Small diff,yes but I like my 38/24 and a 36/22 is too low. I will gladly give up my 11t for a 40 or 38t. A 12/40 cassette will be nice!

  6. @Tim A. To get a 10 speed with a range comparable to xx1/xo1, all you need is to get the 9t microdrive hub and conversion cogs from Canfield Brothers, then put on either the absolute black or the oneup cog on there. And you will save yourself the cost of purchasing an 11-speed shifter, derailleur and chain. Check it out.

  7. I got an idea for these up-and-coming components makers: Take a page out of Apple’s book and announce something at the same time it’s available for purchase. At the internet speed that everything moves, consumers aren’t willing to put a sticky note on their computer that says, “But this thing in January.” They want it now, or they don’t want it at all.

    I read this article and had my credit card out. Until I saw the release date. Guess what? This product will now be forgotten by me because I will eventually find something just as good that’s available now. How awesome would it be if this guy announced this 40-tooth chainring, working in stealth mode up until today, and had the order page ready to go on his website at the same time?

  8. Pete// You also need a rear hub with XD driver as well and we all know nice hubs aren’t cheap. I think it’s a great alternative to someone who wants the simplicity of 1x without loosing the lower gear ratio. I am personally really happy with my previous 1×9 and now 1×10 drivetrain.

  9. Does this have to be used with a certain model of cassette like the one from OneUp?

    @Pete – Let me know where you find XX1 or X01 derailleur, shifter, chain and cassette for $600 to $700. Also, you forgot to add in the price of a new rear hub that most of us will have to buy to adopt.

  10. @pete I can get the XX1 but I prefer the shifting of Shimano. I already have XTR and want to keep it. I would also like a little more low end so a 40t might be the solution.
    @David I completely agree with dumping the 11t

  11. Pete-Because most people can’t justify the cost. Its’ stupid expensive even if you buy it at wholesale (which by the way just went up a wee bit) And as James pointed out…..you’ll still need the new driver ($80-$120 depending on your hub)….if your hub is even in the running. If not, new wheelset. FYI Wholesale on xx1 is almost $860 now before tax with everything you need. No one needs to discount xx1 or “put it on sale” either at his point…it’s in and out of stock lately.

    $100 for a cog that’ll likely last 2-3 cassettes (Yes I know chains stretch, but the effect is rarely felt on largest cogs only smaller…and let’s face it cheap skates will make it work longer) is a steal. Hell most people can sell there front der/left shifter/leftover ring(s) for $100+.

    Reality here is this and OneUp’s solution both are very good solutions to what most of us are running. And as someone who’s loved 1×10 for a few years I have only two concerns: Having a good top end gear and having a better low. I like a 34t or 36t ring up front to get a good cruising gear, but feel it on some climbs the other way….a 40t or 42t option would be perfect.

    Kudos to all these guys for coming up with a worthwhile workaround.

  12. @Geeves, most suspension designs are optimised around 1 chainring size, so even if they have a triple they will work best in only one of those gears, as most people spend the majority of their time in the middle chainring, the suspension is usually optimised around a 32t chainring. No idea what setup you run but if you were running say 38/26 then the suspension is not going to perform as well as it would with a 32 or 34t chainring. 1x drivetrains allow suspension designs to be optimised for 1 chainring and perform better for more of the time. The benefits of 1x on MTB’s are huge, not just in gearing, but in frame design as well.

  13. I just don’t get why a 40T is “a better solution” than a 42T … Seriously, the 36-42 gap isn’t as big as it seems (you barely notice it), you actually feel a LOT more the gap left by the missing 17T cog (or even worse, by the 15T cog if you choose to remove this one).

    And stop with the “I’ll just remove the 11T”, you just kill the point of the bigger cog ! if you remove the 11, you end up with a 11-36 cassette but you’ll need a bigger front chainring. The point of this cog (or any other solution of 40-42) is to keep the WHOLE range of 11-42 (or 11-40).

  14. To each their own. I find the 36 to 42 gap HUGE in racing or training situations (~17%), and I seldom use the 11 (which, from a mechanical standpoint, is an incredibly inefficient gear).

    I’d buy a 12-40 cassette from Shimano or SRAM in a heartbeat and give it a whirl. Until then I’ll stick with 2 x 10 for endurance racing.

  15. Give me a cassette with aluminium spider for 6 biggest cogs and range 11-13-15-17-20-23-27-31-36-42 and take my money!!
    The biggest ratio jump is between 11-13 and 17-20 (both 18%).
    I have the same jupmps on my current 9spd XT cassette and haven´t absolutely any problem with it.
    I hope one day somebody from shimano get it!

  16. this whole thing is stupid.

    people need to give their OCD a rest and ride more, and worry less about a few more or less teeth here and there. Everyone is so obsessed to make an “ideal” 1x set up or save a couple dollars.

  17. Hi,
    Marcin @absoluteblack here.

    I think Ron G. and bz nailed it here already but i will reinforce that.
    42T ring in our opinion is not good solution for most frame designs + current non xx1 rear mechs. Majority of people is facing issues with B tension screw, “wrong” position of hanger to get such spring tension and so on. Leaving alone that when you screw b tension to max, rear mech no longer works like before. Try yourself with your current setup and see how it performs on lower end of cassette (11-13-15).

    Second thing – the “range”. Many do lots of different calculations on the paper saying X>Y. But when i am out with friends doing trail or enduro riding none of them uses 11 or 13T. Same with people we pass on the trail.
    Lets face it- when you go up you use top half of the cassette only (mostly just 2-3 cogs) and when you go down you are sort of in mid range on the back. You don’t drop to 11 or 13T (or even 15T) as firstly chain would become too loose to properly secure N/W ring in gnarly conditions and secondly such gear is terrible when picking speed from switch backs. So in most cases you don’t use two bottom gears at all!
    There is a reason why most popular front rings are in size of 30/32 these days.

    If you really do need huge range because of your riding style or riding XC, then 1×10 is most likely not for you. Not to mention such conversions like ours. We try to nail the problem where rider consciously recognize that he only uses 3/4 of his cassette and needs this one more easier gear for uphills.

    What i recommend is to remove 11 and 13T and put in place 13T with serrations + adequate lockring. This saves you very important 17T cog which is used quite a lot when going down! We are sourcing such 13T end cogs, so we should be able to offer them along our product.

    yes i did make a mistake with “tooths”. English is not my first language, so promise to hire copywriter from now on:)


  18. why is everyone so concerned about making these “minor” adjustments to their cassettes?
    give the 1x setup thing a rest, and/or spend a few extra dollars for a different cassette.

  19. funny how everyone suddenly decided they needed custom wide range cassettes after XX1 came out, when these could have been put together a long time ago

  20. Soooo… if none of you are using your 11T cogs…. you’re all over geared.

    Drop down to smaller chainrings, and all of a sudden you’ll use that 11T, and you won’t need that 40T or 42T out back.

    Lets take a 36T ring with an 11-36 cassette. We don’t use the 11T, so our highest used gear is 36×13. That’s 76.5 gear inches (on a 29×2.1).

    So our low gear of 36×36 is 27.6 inches, and that isn’t low enough. So we want a 40T cog. 36×40 gives us 24.9 gear inches. Better!

    What if we just dropped that 36T ring for a 32T? Now we have a 32×11 at 80.4 gear inches (higher than that 36×13), and a 32×36 at 24.6 gear inches (lower than the 36×40).

    So we’ve got a more useful range and we didn’t have to kludge a cassette together to do it.

  21. Some may not use the 11 or 13t cogs but I sure as hell do! It’s nice to have the option to use it on road sections or on different trails, my trails at home are pretty flat and i use the 11t a lot, my trails at university are stupidly hilly and have some properly steep climbs and some mega fast descents, I want a wide gear range that can cover all bases and all trails. 1x systems are simpler lighter and offer no end of benefits to frames design as some have been mentioned. Granted they aren’t for everyone but people should really try these things and open their minds rather than simply dismiss or pick fault with a new product.

  22. mateo,
    Please notice that many people already use 28/30/32 up front right now. 36/38T users are in minority.
    So you can see that for many 28-32Tx36 is already not low enough.

    Like i wrote before, if you finding yourself using 11T a lot on your setup then you definitely do not need 40T on the rear as you are fit/strong enough:)

  23. I agree that most people should just use a lower front gear, but having more options isn’t a “bad” thing. If you don’t want it, don’t buy it! Some people may not want to change their setup up in front or the derailleur, so this is an option to do it differently.

    Personally, I run 1×10 with an 11-36 cassette and 32t front. I rarely ever use the 11 unless on road or long sustained non-technical downhills in the mountains. 32 front 36 rear is all you should really need for regular riding unless you are trying to go straight up the side of a mountain, much lower than that and it would be easier and faster to just hike a bike up. For the trails I ride, that range is more than enough. However some folks might have different stuff up front and this could work for them.

    People may make fun of you for riding a smaller front Chainring, but if you know how to spin and use it efficiently, it doesn’t matter. Plus for you WWs, it’s lighter to boot!

  24. I ordered a couple of Absolute Black chainrings (30t 64bcd & 34t 104bcd) a while ago Which I’m pretty happy with.
    Currently running 34t x 11-36 & haven’t run out of gears yet.
    I hope we start seeing some bigger narrow wide rings soon; so we can get the 1x cx & road party started.
    Cheers Marcin.

  25. I’ve been reading all these replies and at first I just didn’t get all the negativity. Then Tom cleared it up….you all race….now I see the bickering.

    But I have to tell ya, for those of us that just like to ride our bikes…..these ideas by OneUp, Wolftooth, and now Absolute Black are pretty effing awesome. Keep it up. I’ll be buying the first one that comes out in RED…..that’s a hint.

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