e*thirteen has jumped into the oversized cog cassette adapter fray with two solid looking and well priced options.

The new EX Cog comes in a 40-tooth size for use with 34t max cassettes, in Shimano tooth profiles only. There’s also a 42-tooth cog to go with 36t max cassettes, with ramps and profiles timed for either SRAM or Shimano, helping ensure they work as well as possible with each brand.

Bonus number one: They come in colors – red, blue and black, to be exact. Bigger bonus? You won’t have to blow your bonus to get one. Retail is set at just $69.95 each. Beyond all that, they’ve gone out of their way to make it easy to upgrade your existing 1×10 or 2×10 setup by offering cassette compatibility charts and extensive how-to instructions on their website.

Cogs come with longer replacement B-limit screw for derailleurs since the stock screw could easily get maxed out, particularly on the 42t setups. They say it may not be needed on some 40t installs depending on dropout shapes and angles.

The compatibility chart not only covers cassettes, it also shows which 2×10 drivetrains can work. Chain wrap capacity will be an issue when used with some double cranksets. They also do not recommend using the 40t with 36t max cassettes – best to stick with the 36-to-42 and 34-to-40 upgrade patterns. Why? The ramp patterns aren’t optimized for transition between the two.


Like the other brands’ offerings, you’ll need to remove the 15t or 17t cog in the middle. And ideally you’ll have a medium or long cage rear derailleur. Charts, instructions and more here. Shipping to stores May 15, 2014.


  1. Weird that you can’t use the 40t with a 36 max cassette. How did Hope get around that then? Seems like a design flaw to me… but I’m just a stupid arm chair mechanic.

  2. I’ve been running the OneUp 42T for a while and just got their new 40T. Both work really well on my XT 11-36 10 speed cassette. The OneUp 40T shifts especially well.

  3. Charlie – Link works now. We accidentally published this about 12 hours early and e*thirteen’s site hadn’t made the info public. Our mistake (sorry, Chris!).

    Tad – most likely it’s simply the way the ramps, tooth profiles and such are shaped on the different cogs. They’ve designed each to work best with a particular cassette (optimization!) rather than make something ho-hum that’ll work with anything.

    BT – 16t cog you say? Check back tomorrow (Thurs, April 3) for a little something you may like.

  4. After Cycle Dynamics went belly up (they made individual gear cut cogs and spacers) I’m disappointed that someone hasn’t picked up the torch.. CD made all Titanium or stainless cogs, so you could make any range of any cassette possible. I still have one on my road bike, I can make anything from 11-23 thru 11-30. Oh, and the 11-23 (10 sp) weighs 140g including spacers and lockring..

  5. My bike: Spec Camber Comp 2013 with Sram X9 RD (29er)

    removed original cassette: Sram 11-36 (PCxx, cannot remember)
    replaced with WERK (CZ made) 10sp 11-40 in 12-2013 (different STX cogs + 40t AL cog)
    works fine with sram X9 RD, mud, snow
    changed shifter to X.0 as well (no need but faster)
    chain: Campa Veloce C10
    chainring: Race Face NW without chain guide, 30t

    ! single 40z cogs – should be ok with most RDs
    ! single 42z cogs – pay attention to RD compatibility

    I lost myself little bit:

  6. @kenny – If you replace the 11 or 12 (smallest cog) you’re giving up all the range you gain by adding the 40 or 42. If you want a 13-40 instead of an 11-36, just get a smaller chainring.

  7. BB – oh yeah, sorry. It’s been moved to Sunday April 6th. The brand in question wanted us to hold it until they had stock. Stay tuned…and I’m going to ride one today, so there’ll be real weigh in and first impressions!

  8. I’ve put a 1×10 together, a grocery getter sort of bike w/XT 11-34. I’m 68 and can almost always use an easier gear far more ofter than a faster one so instead of dropping the 15 or 17 I’ve figured a way to drop the 11 and maintain perfect clocking from 13 to 15. 40t is on its way and I’ll report again if this works as well as I hope.

COMMENT HERE: (For best results, log in through Wordpress or your social media account. Anonymous/fake email comments may be unapproved or deleted. ALL first-time commenter's posts are held for moderation. Check our Comment Policy for full details.)

This site uses Akismet to reduce spam. Learn how your comment data is processed.