Review: OneUp 42-Tooth Sprocket


Have you ever been frustrated that 1×11 drivetrains cost a small fortune? Well you aren’t alone. At over $1,000 for a groupo, an 11-speed drivetrain upgrade is a big hit to the wallet. As a result, many of us were confined to the traditional 10-speed range of gearing, limited with a 36T maximum cassette sprocket size.

Many riders, like myself, threw their front derailleurs in the garbage bin in favor of a clean, simple life. Until now, running a 1×10 has always been a compromise of either the high or low end gear ratios. Luckily for us, there is a new novel solution that will now allow most riders with a 10-speed drivetrain to upgrade cheaply to nearly the same dynamic range of gears that the 11-speed groupset boasts!


OneUp components will sell you the magic.  Of course there is no such thing as magic, but some ingenious design, engineering, and manufacturing is just as good as magic when it come to OneUp’s 40T and 42T 10-speed cogs.  The idea is quite simple: remove your 17T cog from your cassette and install the OneUp Components 40T or 42T cog at the back of your cassette.  You lose your 17T cog, but gain a massive ability to handle steep climbs with the 40T/42T cog.  The coverage of gears is equivalent to most 11-speed rear cassettes, minus one gear in the middle.  At a 90% coverage range, the modified 10-speed gearing is quite amazing to use.

OneUp has been smart in designing the product: it is compatible with both SRAM and Shimano drivetrains, so long as you can remove the 17T cog.



I chose to install the 42T cog on my Santa Cruz Nomad.  My previous riding season, I choose to ride a 1×10 setup with a 11-36T Shimano XT cassette and a 33T front ring.  This worked great for me, but occasionally it was a struggle on steeper climbs. The 36T rear cog wasn’t quite enough.

The installation of the OneUp cog was just as easy as the installation of a new rear cassette.  After removing the old cassette, the OneUp 42T cog installed easily on my rear hub.


The reinstallation of the XT cassette minus the 17T cog went just as flawlessly.  Setting up the rear derailleur and chain length took a little bit of effort, but I experienced no issues. I found that I needed to adjust the limit screw controlling the distance between the cassette and the rear derailleur to the extreme end of the travel to allow for enough space between the parts. Once the spacing was set, a quick shift through the gears felt smooth and precise.

The OneUp website provides very detailed installation instructions that were quite helpful.

Out on the Trail


I had heard some warnings that a third party cog would ruin the tight-click shifting of an XT drivetrain.  Boy were the rumors dead wrong! The cassette shifted into and out of the 42T cog smoothly and at command, with no hesitation.  If I didn’t know I had installed it, there is no way I would have known based on shifting performance alone.

Most times I find I shift by two gears at a time in the rear, so I didn’t miss 17T cog one bit.

The goal of the upgrade was a complete success.  I was able to bail out into the 42T on brutal climbs, and stay on the bike when I would have definitely had to hike otherwise. One awesome side effect of this expanded gear range is that I gained some climbing confidence and found myself attempting climbs I never would have dreamed of before.


Bottom Line

OneUp components have delivered a quality product which has a great market base.  I am constantly asked about it on the trail, and other riders are keen to try it out.  The 40T-42T aluminium cog does not add much weight at 51g for a typical upgrade, and is a huge bang for the buck upgrade for anyone wishing to switch to a 1×10 drivetrain.

MSRP: $90 for the 40T sprocket, $100 for the 42T.

A big thanks to the folks at OneUp for sending the 42-tooth cog over for review!