42 Tooth Cog for 10 Speed from OneUp

A New 11-Speed Alternative

Words by Morgan Taylor. Photos by . Video by . Posted by
November 28th, 2013

The big 42 tooth cog on SRAM’s 11-speed XX1 and X01 drivetrains is an object of desire. While there are a number of other innovations present in SRAM’s system which other companies are endeavouring to bring to market, the 6 extra teeth out back were just not available for two-ring or 10-speed holdouts.

Enter the OneUp Components 42T Sprocket. Compatible with both SRAM and Shimano 10-speed systems, OneUp’s 42 tooth design drops the 17 tooth cog from a standard 11-36 cassette to make room for the new piece.


The OneUp 42 tooth cog slides in under the big cog of a 36 tooth 10-speed cassette, displacing the 17 tooth cog down the line.

The result is a 10-speed 11-42 cassette with the following gears:


This does, of course, make for a four tooth jump lower down on the cassette, but riders looking to get more range out of their 10-speed system may not use those gears very often anyway.


Compatible with most 11-36 cassettes from both SRAM and Shimano.

The swap to the aluminum OneUp 42 tooth results in a claimed 51 gram weight increase, which could in theory be offset by dropping a ring up front – but there’s a good chance people will want to keep their granny ring anyway.


The OneUp 42T is milled from a chunk of 7075-T6 aluminum and is available in both black and green anodizing.

At a cost of $100, the OneUp 42T combined with one of the 104 BCD “narrow wide” or “drop-proof” chainrings on the market could make for a relatively inexpensive way to achieve that 11-speed gear range and single ring simplicity.

We have a test piece on the way; stay tuned for an on-trail report soon.

UPDATE: OneUp is offering a $15 discount to anyone who mention this NSMB article when buying a 42T Sprocket by December 18th. Email [email protected] with “” in the subject line to get the discount code.

OneUp Components

Could this be the piece that gets some of the 9-speed stalwarts to upgrade to a clutch derailleur? The piece to keep budget low while upgrading your 10-speed setup?

  • hbelly13

    Uh, yes please!!!

  • Johnny Laroux

    Now this could be a game-changer! I’ve been running a RF Narrow-Wide, but kept my 26T “granny” and do the foot shift as per someone’s suggestion in another article. This could make that redundant…at a lot less cost than going full XX1 or XO1.

  • Oldfart

    But how well will a non XX1 derailleur shift into a cog size larger than it is designed for? I know people are doing that with other 40 and 42 cogs but it sounds from the reports that shifting is merely OK.

  • MrDirtt

    That…is really cool.
    So tempted to try dropping the granny (is a 28 tooth REALLY a granny anyways?) and use with my 39 tooth front ring.

  • sridout

    Help me out here, feeling a little more mentally slow today. Do you get a full cog set for $100 or just the one 42 cog?

    • C.Lee

      obviously just the cog

      • sridout

        If it was obvious I wouldn’t of asked the question. No need to be a dick! $100 seems a lot. I can a by a full set for that.

  • robjob118

    Sounds like a good idea in theory but will 10spd Shimano derailleurs work with a sprocket this big? The “shadow assembly” on the top of Shimano R derailleurs may need to be longer to in order to accomodate 42T.
    You may be stuck using an XX1 or XO1 R derailleur since they’re the only derailleurs on the market that are designed for this sprocket range.
    If Shimano 10spd derailleurs are compatible then I’m sold.

  • megrim

    That looks awesome! Does anyone know if there is something like this, but in a 40 or even a 38 tooth. 30t front ring with a 36 tooth rear cog is just barely not enough for me, but just barely. Looking forward to the review!!

    Morgan, any chance you’re going to stuff that thing on a downhill (or dare I say free ride) bike? See how it does?

    • morgman

      It’s most suited to a trail bike that actually gets pedaled – that’s how we’ll get the most mileage in quickly. Not many people truly pedal their DH or freeride bikes.

  • willywonka

    Review soon please! Crossing fingers that this product works flawlessly…

  • morgman
    • willywonka

      Any chance we can get a short-term review before Dec 18th? If this thing rocks – it would be great to throw some love behind these guys!!

      • morgman

        A test piece is in shipping. We’ll do our best.

      • DC

        @Morgan, any preliminary thoughts would be helpful once you get it, even regarding setting it up. If it’s possible to test it with both Shimano and SRAM drivetrains, that would be even better.

    • morgman

      Sure thing, please leave your questions in the comments here.

  • Vikb

    I use cassettes with multiple cogs on one carrier to prevent them from digging into the fairly soft AL freehub body on my Hope hubs. Looks like that won’t be possible with these 42T cogs.

    Anyone see that as a problem?

    If not what hubs are you using or do you not care about the damage to a soft freehub?

    Looks great otherwise. Thanks for posting. 🙂

  • somemorestuff

    you can get a cheaper steel version already – probably a lot heavier though

    • Benno

      I am surprised that from the pictures it looks like this one has no shift ramps.

  • GladePlayboy

    I emailed them yesterday inquiring about the hub gouging probability. They said it hasn’t been an issue with their testing as the carrier portion of the cog is 4mm thick. I would hope that the tolerances are tight to ensure no movement on the freehub.

    • Vikb

      Thanks for checking GP. That’s good to know. I was planning on a 1 x 10 setup on my new bike. I’m not sure I need more than 36T, but this seems like a good option to keep in mind.

  • amrskipro

    I pulled apart my XTR CS-M980 11-36T last night (recommended as compatible by One Up Components).

    I think with the range of trails, I ride and the fact that one is rarely ever pedalling (for speed) on technical trails once they head down hill, certainly not in 11 or 13T anyway, that dropping the 15T makes more sense.

    That would give a range of 17, 19, 21, 24, 28, 32, 36, 42 for normal trails and a drop to 11 & 13 for the road ride home or the rare (for me) fire trail descent.

    I am running a 36T large ring at the moment (26T granny).
    From a torque and shifting POV I would prefer to see a 40T large ring and that way most decent riders could get away with a 34T or 36T single N/W ring on the front.

    • morgman

      This seems completely reasonable, and I would agree that I’d rather lose the 15 than the 17.

  • hongo52ak

    I’m really interested in this 42 tooth cog. How can I get the coupon code? I’d like to try it on local trails in Japan. Thanks.

    • morgman

      I put the instructions for the discount code at the end of the article.

  • slimdog

    Can we still look forward to a review on this?