OneUp Components 40tooth replacement cog for mountain bike cassettes

After starting with a 42-tooth replacement cog for 10-speed mountain bike cassettes, OneUp Components joins Hope Tech in offering a 40-tooth option.

The new sprocket was designed specifically with Shimano’s Zee FR rear derailleur in mind since that mech couldn’t work with the larger 42-tooth ring. We’re thinking it’ll find a wider audience than that when it comes in stock March 17. From OneUp:

The new 40T has all of the same tried and trusted features as our 42T. It’s compatible with most SRAM and Shimano 10X rear derailleurs, no need to be limited to just one drivetrain company! It’s machined from 7075-T6, weighs in at 70g and has 8 upshift points and costs $90 including shipping.

Nick at OneUp also mentioned the 40T is compatible with Saint rear derailleurs when the mode converter is in Freeride mode. They’re still testing with Sram short cages, so can’t yet recommend the 40T with anything other than medium and long cage SRAM derailleurs. Their full compatibility chart is here. More pics below…

OneUp Components 40tooth replacement cog for mountain bike cassettes

OneUp Components 40tooth replacement cog for mountain bike cassettes

We’ve been testing the 42T cog with good results. First impressions posted here.


  1. I imagine I would rather loose the 15 instead of the 17, buy a single 16 tooth cog and use that gapping in the cassette instead.

  2. Awesome, I just bought a zee der and was having a little buyers remorse since you can’t get the canfield capreo hubs with just cogs you need anymore, only a whole $150 cassette. Think I’m gonna get one of these, maybe not even run it all the time, just swap it and a chain on for epic climbing days.

  3. This setup can place some demands on your rear hub. Shimano outlines this in their service instructions with their 12-36 cassette and recommends a stronger free hub. Something worth exploring more…

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