The next stage in the build of my Salsa Mukluk fatbike which I am configuring for bikepacking is the specifying of the drivetrain, a SRAM based 1×10 drivetrain with a OneUp 42T Sprocket + 16T conversion. This post details my thinking and research into the drivetrain specification. Hopefully it will be helpful to others considering the options.
My intention is specify my Salsa Mukluk as a bike for bikepacking, a touring bike and just as a fun fatbike and mountain bike so it will be built to run fat wheels and 29+ wheels. With this in mind I have decided to go with a 1×10 derailleur drivetrain configuration rather than a Rohloff setup. I also think the Rohloff is steeply priced and I am struggling to see the $1,000 of value in the system.
With the Salsa Mukluk I am using Surly Marge Lite rims which are a 65mm rim width. The tyres will be around 3.8” in max width. Based on Surly’s tyre geometries I am looking at a maximum casing width of 95mm. This pretty much counts out a triple crankset with a couple of exceptions so my realistic options are 1×10 or 1×11 or a 2×10 drivetrain. My initial plans had been to go with a 2×10 drivetrain but over time I have swung over to giving serious consideration to a 1×10 or 1×11 drivetrain. This post goes through my research on the 1×10 and 1×11 options.
While SRAM has now introduced a lower priced 1×11 and a 2×11 groups, all the SRAM 11 speed cassette require a SRAM XD Driver Body and hence a compatible rear hub. My frameset came with a hub, but of course it is a Salsa Mukluk 2 rear hub rather than a Salsa Fat Conversion rear hub which can be converted to take the XD Driver or the Salsa Conversion 2 XD Fatbike rear hub which is an XD Driver hub.
Even with the reduced pricing on SRAM GX, adding in a new hub and possible SRAM XD Driver has really priced the SRAM 1×11 drivetrain out of the ball park for this build.
Shimano XTR M9000 drivetrain is the other option which has the advantage of using a standard Shimano compatible hub. The downside is that is limited to 40T which is really not going to be low enough for me as the gear inch table below shows.
The third option is to convert a SRAM or Shimano 10 speed 36T cluster to a 40T or 42T cluster. As noted above I do not believe 40T is going to be sufficient so with this option I am looking at a 42T conversion.
One such option is the OneUp 42T Sprocket + 16T conversion which appeals to me as it comes complete with a 16T sprocket to replace the existing 15T and 17T sprockets. Going with OneUp and Shimano also means having to replace the outer cage with a OneUp RAD or RADr cage, another complication. Being a SRAM fan-boy I have decided that with this option a SRAM 1×10 conversion base is preferred. I also like that I can get a single right shifter easily for SRAM.
As the table shows below, the lowest gear inches are the same for the SRAM 1×11 and SRAM 1×10 OneUp conversion at 17” but higher with the Shimano 1×11 at 17.8”. The variance is more at the high-end which may come into play as this bike will be both a fatbike and a 29+ bike.
Using Sheldon Brown’s Gear Calculator I set the wheel to 26 x 4.0 / 102-559 fatbike at 10 PSI and the crank length to 175mm. The resulting gear inches for the different combinations are reported in the table above.
|SRAM 1 x 11||SHIMANO 1 x 11||1 x 10||2 x 10|
|Kmh @ 90 RPM||7.3 to 30.8||7.9 to 33.1||7.7 to 28||8.3 to 30.1||7.3 to 28.0||7.9 to 30.1||7.2 to 21.7||12.8 to 38.5|
One option I didn’t consider with the 2×10 drivetrain is a 22T x 42T combination which would give me a seriously low granny gear I suspect. I will leave that there on the table as a possible option down the track.
As I alluded to above, the more I reflected on my drivetrain setup, the more my thinking was towards the simplicity of a 1×10 or 1×11 drivetrain. J.A. Caldwell at Old Glory MTB argues that running a 1X drivetrain has the following advantages:
- Lightweight – reducing weight on this bike will be beneficial for sure;
- Simplicity – only changing the rear derailleur; no oh sugar in the wrong gear up front;
- Lower maintenance – no front derailleur to maintain;
- More ground clearance due to using a smaller chainring up front;
- Quiet drivetrain – apparently the clutch type rear derailleurs reduce chain slap.
More recently MTBR.com has published a Tech document on 1×10 drivetrains, titled Tech:Deep dive on 1×10 narrow/wide conversion gearing which also shows the advantages of a 1×10 or 1×11 drivetrain.
All this has led me to a deciding to go with a SRAM 1×10/Race Face Turbine Cinch/OneUp drivetrain with a 42T Sprocket + 16T conversion as being the best bang for buck.
The key driver from my crankset/chainset setup was the availability of (1) 26T wide/narrow chainrings and (2) that I consider direct mount a desirable feature and oh the crankset needs to be available to fit 100mm bottom brackets.
The choice for me came down to either a SRAM X9 crankset with a removable spider or a Race Face Turbine Cinch. Both cranksets are 104/64 BCD which means that there is a good range of suitable 64 BCD chainrings. The SRAM X9 direct mount seems to have a wider choice of chainrings than the Race Face direct mount but there are still plenty of choices for Race Face. The key aspect of the Race Face Turbine Cinch that swung my decision in its favour is that is flexible and upgradeable. Oh I also like the way it looks. As it turned out I was able to get a Race Face Turbine Cinch at a good price from Ubyk Ltd in the UK so deal done.
I decided to go with a 26T Race Face NEXT SL Direct Mount Narrow Wide tooth profiling single chainring and a Race Face BSA30 Bottom Bracket to complete the crankset.
As alluded to earlier, this is a SRAM 1×10 build with a OneUp 42T Sprocket + 16T conversion. The rear cassette is a SRAM PG-1070 12-36T 10 speed cassette with a OneUp 42T Sprocket + 16T conversion.
The rear derailleur is a SRAM X9 Type 2.1 [Clutch] Long 10 speed derailleur and the chain I am going to start out with is a Wipperman ConneX 10sB black edition chain.
Nokon cables will be used to connect the rear derailleur to the SRAM X9 10 speed trigger shifter completing the drivetrain configuration.
So there is my planned 1×10 with . Now I need to gather the components to complete this part of the build.