29+ Bikepacking Granny Gear: Surly OD Crank vs Wolftooth vs Rohloff

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The Surly OD Crank is a pretty piece of metal, not to mention one of the only options for setting up a 2x system on a 29+ bike… and one of the few options for yielding a granny gear for bikepacking. Also, a comparison by the numbers…

I have already touted the many benefits of the 29+ platform, so it shouldn’t be a surprise that I recently added a Krampus to the stable. The Krampus comes set up with a 1×10 drivetrain, out of the box. This could make climbing a little rough if you have it loaded for a bikepacking trip through steep and rugged terrain, like that of Pisgah. For now, here are my thoughts. Lots to nerd about when you’re talking Monkey Nuts with granny on a Krampus:

Surly OD Crank - 2x10 on Krampus, ECR, 29+

One pretty piece of metal.

There are a couple options for putting a true granny gear in the drivetrain of the Krampus, or the ECR. Ultimately I would like to have my Rohloff set up for both so I could switch the back wheel, but that’s not in the cards for this iteration. Plus, I’ll be using the Krampus as a trail bike as well. The simplest alternative would be to add a 42t Wolftooth cog to the cassette. This would provide a granny(ish) gear and keep the sleek 1x setup. The other option is to add a front derailleur and a capable crankset with a wider chain line to get around the beefy 3” tires for a 2×10 setup. Note: the OD has a chain line that’s about 6.5mm wider than a traditional Shimano 2x crankset.

Surly OD Crank - Bikepacking Granny Gear

A pretty piece of metal comes in a pretty box.

I opted for the latter option, obviously. I bought a cheap SLX front derailleur and spent some time in the garage mating it with the OD. Getting it all bolted together was easy, but tuning it was a different story (although I can’t claim to be an excellent wrench when it comes to derailleurs). When I first started toying with the OD I had a few issues including the Shadow derailleur hitting the chain when the wheel was mounted in the rear dropouts using Monkey Nuts (Monkey Nuts clamp into Surly horizontal rear fork ends (aka dropouts) to make spacing the wheel back easy). Also, the front derailleur required some finesse. In the end I ditched the Monkey Nuts, but eventually I will probably get a different derailleur in order to reinstall them and add a little space between the tire and seat tube. But nevertheless, it works beautifully and I have a true granny gear. For shits and giggles I thought I would take a look at some numbers in comparison to the other options and put the 29+ granny gear in perspective… or complicate it depending on how your mind works.

Surly OD Crank - 2x10 on Krampus, ECR, 29+

A little space between the frame and the Knard, but the Monkey Nuts would back the wheel up and give it a little more clearance.

Chain Inches: Wolftooth vs Surly OD vs Rohloff

To do this I will illustrate each of these drivetrains on a 29+ (3” Knards) using gear inches. From Wikipedia: Gear inches is one of several relative measures of bicycle gearing, giving an indication of the mechanical advantage of different gears. Values for ‘gear inches’ typically range from 20 (very low gearing) via 70 (medium gearing) to 125 (very high gearing); as in a car, low gearing is for going up hills and high gearing is for going fast. Essentially to calculate gear inches, use this simple formula: Gear Inches = Wheel Diameter x (Chainring Teeth/Rear Sprocket Teeth).

Surly OD Crank

Here are numbers calculated from my Krampus setup. For each of these I use the lowest three gears to show range:

  • Crankset: OD Crank (39/26t)
  • Cassette: 11-12-14-16-18-21-24-28-32-36t
  • Granny gears: 22.2 (26/36t) / 24.8 (26/32t) / 28.3 (26/28t)
  • High gear: 108.1 (39/11t)
  • Edit: Switched to 36/22 18.6 low / 99.8 high

Wolftooth Components 42t Cassette Cog

This is a pretty cool cog replacement for enabling a granny gear on a 10 or 11 speed cassette. The installation procedure involves removing the 16, 17, or 18t ring and adding the 42t Wolftooth to the back. For this example I referenced a 32t front chainring on a traditional 1x crank. A friend of mine uses a 30t, but there is chain rub with the Knard when engaged with the 42t Wolftooth ring, so he is planning on switching to a 32t up front which should do the trick.

  • Crankset: Traditional with 32t ring
  • Cassette: 11-12-14-18-21-24-28-32-36-42t
  • Granny gears: 23.2 (32/42t) / 27.1 (32/36t) / 30.5 (32/32t)
  • High gear: 88.7 (32/11t)


I was actually pretty surprised at these numbers considering a 38t/16t ring combination on my ECR almost killed my knees. Of course that was with racks, and a load for international travel that included all of this stuff. About 2 weeks into our Africa tour I ended up switching to a 34t and here is what I was getting:

  • Crankset: Traditional with 34t ring
  • Rohloff: SpeedHub 14sp with a 16t ring
  • Granny gears: 18.1 (1) / 20.4 (2) / 23.3 (3)
  • High gear: 106.8 (14)

So, in conclusion, the Rohloff gets the lowest granny gear (18.1 gear inches). However, the 2×10 gets a slightly better range with a low of 18.6 and a high gear of 108.1 (vs 106.8 on the Rohloff).

Surly OD Crank - 2x10 on Krampus, ECR, 29+

Not much space between the front derailleur and the edge of the Knard. Again, adding Monkey Nuts would back the wheel up and allow a little more clearance.

Surly OD Crank - 2x10 on Krampus, ECR, 29+

The widest chainline swing: 39/36t.

Now, if you made it down here, go drink a beer or two and burn off that nerd knowledge.


  • http://www.gypsybytrade.wordpress.com/ Nicholas

    Logan, I found the 39/26 to be a little high for a 29+ bike, especially as it comes on the stock touring-minded ECR in this same chainring configuration. Also, the 5-bolt pattern is a bummer, as I prefer to stick to 4-bolt 104/64mm BCD for easy chainring selection. Lots of cheap 104/64 rings out there these days, and also the pattern for which you will find a 1x specific ring, such as a RaceFace or WolfTooth, if you choose.

    Finally, while the combination creates chain to tire clearance, the outer chainring and inner rear cog make for an unhappy chainline, It works, but creates unwanted noise an friction. Now, the real test is to pedal it backwards in that combination. At least in my experience, the chain may drop to the next cog down. This doesn’t seem like a common possibility on the trail, but when riding trails, such things happen (riding fast, shift to climbing gear in rear, relocate pedals over technical climb by backpedaling, ohshit the chain dropped!). Ok, worst case scenario, but as Surly says, “we make stuff for the worst case scenario).

    You think that’s a pretty piece of metal? I might just call it a functional piece of metal. Looks like a chunky Andel crank with some heavy-duty rings.

  • Skyler

    What’s the trouble with putting your Rohloff on the Krampus. Shouldn’t a Monkey Bone disk adapter be all you need for that?

  • http://www.pedalingnowhere.com/ Logan

    Hey Nick. I took it out yesterday on the Uwharrie trails here in NC. There are a couple decent climbs there so I got to stretch the gears out a bit. I never had a noise problem, or lost the chain, but I also never have it in 39/36… it doesn’t really make sense to use that combo anyhow. I’ve found the best way to ride a 2x setup (especially one with a wide chainline) is to use the inner ring as much as possible (it has a better chainine) and then use the outer for only the smaller 6 or 7 in rhe back. I hear you on the 4 bolt argument, but at the same time, if you aren’t counting grams, those surly stainless rings will last 20,000 kms.

  • http://www.gypsybytrade.wordpress.com/ Nicholas

    Yes, all good points. I prefer to consider a double like a 1x with a bailout gear (which I use more often than the name suggests, at least in a loaded application). With the big ring, the chain and derailleur create more tension and less chain slap and less ghost-shifting under extreme circumstances– this is the theory behind all the clutch derailleurs these days, and the reason DH riders used to descend in the big ring.

    I don’t entirely dislike the Surly crank– it provides a genuine solution to 29+ geared bicycles– but it is imperfect. The industry designs cranks with specific chainlines for a good reason (shifting performance and wear). At least on some fatbikes (such as the Muk2), the Surly OD crank would derail when pedaled backwards in the big-big combo. It’s a weird thing, but it also suggests a poor chainline when pedaled forward.

    One final caveat is that I currently design my drivetrain with a 32T cassette in mind. These are cheap and easy to replace when needed. For this application, 36T is a bit high. The 39/26 never made much sense on the ECR, even for unloaded applications.

  • http://www.pedalingnowhere.com/ Logan

    Hi skyler. You’re right, it shouldn’t be a big deal to set up. But, I have the 36 spoke Rohloff and I wanted to see what wider rims did for the footprint of the Knards (and ultimately the Dirt Wizards or that new Maxxis tire). Unfortunately, as far as I know, there is not a 50mm+ rim on the market with a 36 spoke drilling…

  • http://www.pedalingnowhere.com/ Logan

    Yeah I think the 22/36 combo would be better for my upcoming trip in Pisgah… big climbs with luggage. That would provide an 18.6 for the granny and a 99.8 on the high side. And regarding the pretty factor, I do like the look of this crank… simple and sturdy. Kind of like the Race Face Sixc.

  • Skyler

    If you’re willing to use a unicycle rim, like the Snowcat, you might find options for a 36 hole 29er rim. But, it might be hard to accept the half pound weight penalty compared to the latest and greatest from Stan’s.

  • Andrew

    I’ve been silently reading the blog here for a couple weeks and really enjoying it – thanks.

    This particular post is one I wish i’d been able to read a few months back when i got my own Krampus and made the same switch to the OD crank right out of the box – and running it without the monkey nuts. I’ve been riding the thing around out here in northern New Mexico – where there are a lot of long hills, and a lot of rocks to backpedal through – several days a week for the past 4 months or so and it’s been great. The gearing could be a little lower for some of the multi-hour climbs (I would imagine this is even more the case were i hauling bags loaded with gear on top of my own 220 pounds), but then again, i could be a little stronger.

    I haven’t dropped a chain, nor encountered any issues with the admittedly nervous-making closeness of the front derailleur and the rear tire. There was one ride where the mud got pretty thick (adobe, as we’d call it out here) around the bottom bracket – front derailleur – giant tire nexus, but even then the only thing that slowed me down was pulling over to look at it and wonder if it’d be a problem.

    The closest thing to a problem with the setup was having to put some spacers in to allow a water bottle cage to fit over the front-derailleur adapter, which was remedied at the hardware store for about 0.80 cents.

    Have fun with the bike, I’m having fun with mine. and thanks for the great blog.

  • http://www.pedalingnowhere.com/ Logan

    Hi Andrew. Thanks, glad you are enjoying it. I posted this because I couldn’t find much info out there either. There were a few hints here and there on MTBR, but I thought this might help clarify things for people who may be searching. Are you also running the 39/26 combo? I also think it could be a tad lower… I am thinking about swapping to a 36/22 for a bikepacking trip next week…

  • http://matthewplummer.org.uk Matthew Plummer

    I’ve just built up my new ECR with 36 spoke Duallys – Velocity did a small run of them and I managed to snaffle a pair. They’re laced to SON 28 and Hope Pro 2 Evo hubs. I’m also thinking of swapping the 22t for a 20t chainring – still mulling that over though.

  • http://www.pedalingnowhere.com/ Logan

    Nice… jealous of those 36h Duallys. I had the 22/36 combo on a 5 day bikepack in Pisgah (just got back); seemed like a great combo for me…

  • Peter Mac

    Hello mate,
    I have just overcome a conundrum and built up an ECR. What a fab frame. It’s using 2 x 9 Shimano XT kit running Blackspire 36/24 fronts with 34 rear cassette. It functions very well for my bike packing needs. I’ve cheated, I guess in reference to 29er plus rear tyre clearance issues, because I actually don’t intend to run the ECR with 3″ rubber. I think there’s enough 2.3 wide 29er stuff out there to satisfy the need. Plus they tend to be much more economical. As I also have a Pugsley, this will form the basis for any fat tyre tourer needs. Also, when I ran my Rolhoff on an earlier situation, I ran a 32 front ring which allowed the use of the top 7 gears. The lower 7 gears tend to be way too draggy and actually make me think unless you’re absolutely “out there”, then a stock derailleur setup is much more sympathetic to one’s knees. Before I forget, there’s no problems with the ECR’s low BB. I think all the forum “chatting” in reference to this is over specified.
    Take it easy and best wishes.

  • http://www.pedalingnowhere.com/ Logan

    Thanks for the input! I used a 34t ring with the Rohloff on the ECR and it seemed like it was geared perfectly for touring/bikepacking. There are a lot of 2.4″ tires out now that make the BB height tolerable on the ECR. However, it really depends on where and what you are riding. I was in Pisgah this past week and used every bit of BB height on my Krampus for logs, rocks, roots, drops, etc. Enjoy the ECR, it’s a great bike!!

  • Andrew

    I’m running the 39/26 combo, yes, and it could be a little lower sometimes.

    Also, had an interesting issue come up with the shifting that I thought I’d ask about. When the bike was originally set up, at the advice of a friend i set the 3-speed shifter (XT RFP shifters) to move between the two rings in the middle and outer settings. Recently i brought the bike in for a tune up and the shop changed this so that it now runs on the inner and middle settings. Seemed like no big deal, and i took the bike out on a long ride. But, the front shifter got some strange tension on it part way through, and then gave out. The bike’s going back in today and I’m advocating for a move back to the original setting, but the guy at the shop wants me to move to some friction shifters (which’d be fine if i didn’t have to buy them) and claims that the problem has to do with mixing shimano and Surly chainrings and chains.

    I’m wondering what you are running shifter-wise and how you have the shifter set up for the front – middle-outer, or inner-middle?

  • http://www.pedalingnowhere.com/ Logan

    Well, I have a dedicated XT 2×10 shifter set, so that probably doesn’t help you any. I got a pretty good deal on them from Jenson USA…

  • JB

    Great post! Been building my ‘dream’ ECR for some time now and decided on the OD and rabbit holes after all. Planning on outfitting XTR front and rear mech and shifters – do you anticipate fit issues based on your experience with the ECR? Thanks for any input!

  • http://www.pedalingnowhere.com/ Logan

    Thanks JB. It sounds like you are on the right track. With the XTR rear derrailleur you should be able to get by with the Monkey Nuts to add a little space… but I am not 100%. You might look on MTBR forums… cheers.

  • JB

    Sounds good, Logan. Does Surly simply get around the space issue by using the 9 speed cog? I guess I don’t understand why there is not a space issue on the stock build. Thanks! JB

  • http://www.pedalingnowhere.com/ Logan

    Ugh. Sorry I wad thinking about the krampus. I am not sure about the ecr… I have a rohloff… sorry.

  • JB

    Oh! No worries at all – I’ll be sure to post some info on this issue as I build things up and work out any kinks. Keep up the great work – love your site. JB

  • Chadman

    Just thought I’d add to this that I’m running an XT 2×10 on my ECR with XT cranks. Just barely clears my 3″ Knards in back. I am running Velocity P35 rims and XT hubs though. Quite sure it wouldn’t work with the rabbit hole rims.

  • Wedge

    I’ve finally bitten the bullet and heading toward the Rohloff crew but I’m trying to mirror the gear performance of the OTP gear setup as I love it. Anyone here able to steer me toward a front and rear chainring combo that might emulate the current set up?

    Thanks in advance.

  • http://www.pedalingnowhere.com/ Logan

    Rohloffs are great. I am unfamiliar with OTP, so I can’t help you there. I do know it’s pretty easy to adjust the gear ratios by swapping out the front ring. I use a 34t ring on my 29+ for bikepacking which gives it a nice granny range.

  • Wedge

    It’s a pretty spinny 1st gear which is great for me (heavy, but getting lighter) and my gear (heavy, but getting lighter also). I’ll start with 34t on the front, what rear would you use?

  • http://www.pedalingnowhere.com/ Logan

    Rohloffs usually come standard with a 16t cog… which is what I’ve always used. If you are on a 29er, the 34t should definitely be spinny? I would move up to a 36 or 38 if it is a 26″ bike…

  • Wedge

    It’s for an ECR so I’ll try the 34/16 and have a muck about. Thanks for the help Logan.

  • http://www.shanecycles.com Shane

    Brilliant comparison thanks, Sadly most of us will never be a two Rohloff family and wheel swapping isn’t always an option with so many different size, brake, frame configurations.

    The Roholff granny gear you now have is interesting and though slightly heavier than the derailleur options I think that is more than compensated for by the Rohloffs’ ability to change gear at at standstill when you hit a rock or pothole that is bigger than you expected it to be. That said I’m considering a 1×1 or 1×9 conversion for some of my future trips where I’ll be carrying the bike as much as pedalling it. After all the Rohloff is a bit on the heavy side and gives a heavy back end.

    At the moment I’m running a 26″ with 36x17t stainless Surly ring (because its the largest 104bcd that they have) which is generally light enough. At the time this was slightly lighter than what was allowed by Rohloff.

    Interestingly Rohloff have lowered the minimum gear ratio (again?) and its now at 1.9 which gives an interesting arthritis granny gear of 32×17 which compares to 20×40 in old money…. http://www.rohloff.de/en/technology/workshop/sprocket_ratios/

    Meaning I’m more likely to order a smaller Surly ring than do a single speed mountain bike conversion :)

  • Gary Sullivan

    Thanks for that bit of math, saved me from doing it. I think on the strength of that I will go Wolf 42 on the back of my Krampus, and stay with the single ring. If me eyes still water when climbing a hill loaded I will look for a 30 chainring. I don’t plan on needing at 88″ high gear for the Krampus, it is for going quite slow all day. Do you know if the SLX derailleur that came on the bike will stretch to the 42? I am pretty sure the cassette is not compatible for that conversion, but I have one already mated to a 42 that might still be within the realms of functionality.

  • http://www.bikepacking.com/ BIKEPACKING.com (Logan)

    Not sure about the SLX der. I would think so, but I haven’t tried it…

  • http://www.bikepacking.com/ BIKEPACKING.com (Logan)

    Thanks Shane. Yeah, that should be fine for a smaller 26″ setup. I had a 38/16 Rohloff setup on my Troll…

  • Ian

    After not being able to find a 36t Surly OD chain ring after six months I decided to go out on a whim and try a Sram GX Boost crankset (36/24) on my Krampus Ops.

    When in the shortest gear, 24×40 one up conversion, it leaves 4 mm between the chain and the tire, I’m running Minnion’s on a RH rim. I’m sure you’d gain a mm with a 36t in the rear.

    In short Boost cranksets will allow you to run 2x either the Krampus or ECR, and you save about $100.

  • goodgnus

    The SRAM GX Boost crankset chainline (measured between the two chain rings on a 2x) is 52mm. The Surly OD is 55.3mm. The Surly OD gives more clearance, for those who want the most clearance.

  • matt

    have you thought about fitting the 11 or 12 cog on the cassette first,this will move the biggest sprocket further way from the rear tyre when your in your lowest gear on the granny ring preventing the chain rubbing on the tyre. matt

  • http://www.alpineluddites.com Alpine Luddites

    i run the 15 cog on my rohloff with 34 up front on 29’r. i found the 16 to low for spinning.

  • fthefox

    Old school square taper BB here with RF Turbines

  • Miles Arbour

    I just installed a 42T Blackspire on my Krampus, 32T chainring up front. SLX der. Had to tighten the b-tension screw all the way in, and adjust the limit screw slightly, but it looks like it is working fine now! If I had a bigger chainring up front I think I’d add a few links to the chain though.

    Easily installation, just took off the 17t and one spacer from the stock Sram 10 speed cassette.

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