Just In – OneUp Components 42T Sprocket Adapter

by Brian Mullin on December 13, 2013

your 10-speed cassette to an awesome 11-42 wide range cassette with the
OneUp Components 42T Sprocket. It’s a low-cost alternative, that’s easy
to install on a 11-36 cassette, and only requires swapping out one cog
from the main cluster.

The 11-speed drivetrain rolled like a
freight train into the mountain biking world when SRAM released their
1×11 XX1 system, and its now joined by the just released X01. The system
uses various front chainrings (28T-38T) combined with a 10-42T cassette
for its 1×11 gearing. The price tag and the requirement of mostly using
a full set of SRAM parts for the drivetrain has kept many people away
from enjoying the benefits of the 1×11 simplicity and smooth shifting of
SRAM’s excellent product. It didn’t take long for third party companies
to jump into the fray to give consumers workarounds for the 1×11

The first workarounds were for 1×10 gearing using the
current 11-36T cassettes combined with narrow-wide chainrings from Race Face, Wolf Components and others, along with a clutch rear derailleur
(SRAM Type 2 or Shimano Shadow Plus). Next came cassette adapters that
use portions of a 10-speed 11-36T, and replacing certain cogs to give a
wider gearing range to more closely emulate the SRAM 11-speed cassettes.
One of the first offerings was the General Lee cassette adapter, which
replaced the last four 24-36T cogs with a 25-40T, but it only works with
SRAM 1030, 1050 and 1070 cassettes, and costs $200. There are few other
options on the market, including the Recon 11-40T cassette, and a
couple of smaller companies operating out of Europe with cog
replacements of some sort.

The latest and most interesting alternative is OneUp Components
single 42-tooth cog, which will come out in January and only costs
$100. The OneUp 42T cog fits at the end of the Shimano XT and XTR, SRAM
X5, X7 and X9 11-36T cassettes, and you remove the inner 17-tooth to
keep it as a 10-speed system. Another interesting aspect of this system
is that you can run it as a 2×10 if desired, though I am not sure what
front gearing you might use. The cog is made from 7075-T6 aluminum,
weighs in at 70 grams, and has 12 up shift points. To help prevent the cog from digging into the soft material of most
freehub bodies, the cog has wide tabs by the spline for a better load distribution.

The initial 2×10 setup on my Ibis Ripley 29er was a Shimano XTR 11-36 cassette, a medium
caged SRAM X0 Type 2 rear derailleur and an E*thirteen TRS+ crankset with 24-34T chainrings.

Test #1
For the first 1×10 test, I used the existing 34T front
chainring and the OneUp adapted 11-42T cassette. I left the rest of the 2×10 components attached, to make initial testing easier, and never used the front derailleur or shifter for anything.

Test #2

For the second test, I removed the front derailleur, front shifter, inner 24t
chainring and replaced the E*thirteen 34t chainring with a new Pacenti
32t, which saved 355 grams. Since adapting the cassette to 10-42T adds
50 grams, I therefore saved 305 gram (.67 lbs) over the 2×10 set
up that I started out with.

pulled the XTR cassette off the rear hub and tossed out the 17 cog and
its accompanying spacer. I then slid on the 1mm OneUp spacer and their
42T cog, and then the rest of the XTR stack (minus the 17T), and cranked
it down to specs. I liked that the OneUp 42T cog had a small arrow
pointing at the notch, so it made it easy to line everything up on the
free hub body. Swapping everything out increased the cassettes weight by
50 grams.

Update – I located an old Shimano 16t cog in my parts bin, so I swapped out the 15t with the 16t to create a more even range in gearing:  11-13-16-19-21-24-28-32-36-42.

Top Photo – 32t front & 42T rear/Bottom Photo – 32t front and 11T rear

wasn’t sure how long of a chain I might need for the 42-tooth rear and
34-tooth front combination, so I bought a new 120 link SRAM PC 1071
chain, and ended using 112 links plus the PowerLock connector. As shown
above, that chain length worked fine for both the highest and lowest
gearing options on my medium X0 derailleur.

I knew that I
would need to crank out the B-tension screw on the rear derailleur since
the derailleur was optimized for a maximum of 36 teeth, and I ended up
getting it close to its limit to keep the pulley the proper distance
from the cog. While in the stand, the derailleur shifted up and down
without any problems, and it all seemed fine until I actually pedaled it
under power while riding, and it wouldn’t downshift from the 42-tooth
cog. So I cranked the B-tension screw to its limit and tried again, and
it still seemed to have an issue with rolling down from the large cog
while under power. I followed OneUP’s
suggested trick of removing the small lock washer on the screw to gain
additional length, and it then shifted properly under power. They even
state that you can reverse the screw to gain more length, though I think
just getting a longer steel one at the hardware store (4x22mm) is a better
choice, and it gives you a spare backup in case you break one, which I
did during my initial tweaking.

First Impressions
how does it ride and shift? It works surprisingly well, and in direct
comparison to the 32T to 36T up shift, there is a slight loss of
smoothness, and a bit more of a thunk during the 19T to 15T drop due to
the missing 17T; otherwise, I didn’t notice any outstanding issues. I
have taken it out for several days of riding, and it shifted flawlessly,
in fact; I would be hard-pressed to realize that I had this gearing
installed on the bike. Although they suggest using a narrow-wide
chainring, I never suffered any dropped chains during my test period
with my set up. I cranked things under heavy loads on some pretty steep
terrain, in both loose and smooth conditions, and the shifting and power
transfer worked fine. I certainly liked not having to roll up and down
through the front derailleur to get my desired gearing options, and I
felt as though I could spin better with the larger chainring compared to
a granny sizing.

Once I had the derailleur tuned properly and
chain at the correct length, the OneUp 42T system has worked exceptional
well, and I really didn’t notice any difference in usage compared to
original 2×10 normal setup (11-36T rear and 24×34 front). I think this
simple system, with its low-cost and fewer part swap outs will appeal to
a lot of people. The $100 price, and maybe a new chain, clutch
derailleur and a narrow-wide chainring will get you a pseudo alternative
to the XX1/X01 wide range of gearing.


  • Wide range 1×10 gearing – XX1/X01 range
  • 1x and 2x usage
  • Low-cost and fewer part swap outs
  • Great shifting characteristics
  • Simplicity – no front derailleur
  • Weight saving –  depending on components used,.6 to .75 lbs


  • Missing 10T cog of XX1/X01 cassette
  • Clunky 19T to 15T shifting (due to missing 17T)
  • Might need clutch derailleur and a narrow-wide chainring (didn’t have an issue with the latter)
  • Only works with Shimano XT and XTR, SRAM X5, X7 and X9 11-36T cassettes

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