Surly Bikes
In my humble opinion, 1X11 setups are the best thing to hit mountain biking since reliable front suspension (I would say clutch derailleurs but they kind of go hand in hand with 1x). No more dealing with stupid front derailleurs or extra rings. Sure doubles and triples have their place, but I think bottom bracket clusters just look so much better with a simplified drivetrain…..but enough of my opinions and on to the nerdy facts.
We’ve recently had some people calling in trying to troubleshoot poor shifting with a new 1x11 setup on their Krampus or Instigator. So for those fine folks and for anyone thinking about making the change to 1x11, I’m going to drop some knowledge on you.
One important thing to note is that this only applies to OD cranks (Instigator and Krampus Ops), the classic green Krampus ships with a Shimano Zee crank which has a different chainline than the OD crank. Also the following information is in reference to 73mm BB shells, our Omni line will have different requirements. Did someone say another tech blog????
The OD crank uses 2 less common BCD spiders, 58 BCD and 94 BCD.
- The 58 BCD spider has a 51.4mm chainline
- The 94 BCD has a 59.2mm chainline.
- Sram 1x11 groups use a 49mm chainline
- Shimano 1x11 groups use a 50.4mm chainline
What this means is that someone wanting to run a 1x11 group on the outer (94 BCD) spider of an OD crank needs to space the chainring inboard 10.2mm for SRAM, and 8.8mm for Shimano to achieve the “ideal” chainline. You may achieve proper shifting at less than ideal chainline, but to remove as many variables as you can, I recommend running ideal chainline.
Another option is to run the Surly Stainless Narrow Wide ring in the 58 BCD position. If you choose this path then you won’t have to do any chainline adjustments. You will probably want to grab our OD Chainring Guard or risk looking like a kid wearing jeans to gym class because your 94BCD spider will be naked and your chainring will be unprotected.
The Surly Narrow Wide ring was designed in conjunction with SRAM and has a 51.4mm chainline on a 73mm BB shell. They have approved this for use with X-sync technology, so there is a little bit of wiggle room.
With great knowledge comes great responsibility. Also, this information is only useful if you are comfortable setting up and adjusting your own derailleur. If you aren't, bring your bike to your local shop and bring them a sixer while you're at it.
Finally, this has nothing to do with 1x11 troubleshooting but I was listening to these guys while I wrote this masterpiece and they wail
About Slippers Cortez
Well hello there, meet Ben, aka Slippers Cortez. Ben is one of the Engineers here at Surly. When Ben isn’t doing bike math and drawings, he’s likely enjoying a beer and playing the mandolin with his brothers in their folk/bluegrass band, The Thirsty River. If you don’t know what a mandolin is, there’s a google for that. If you meet Ben, you’ll notice that he’s the most Minnesotan person you know. We mean that in the best of ways of course. So the next time you're straddling your Surly, think of Ben, because he just might be thinking about you too.