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2016 Surly e-Krampus

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    2016 Surly e-Krampus

    **For any build, I will walk you though issues I have found, but if everything else is standard, I'll leave it out. Also, I may copy and paste segments in the beginning for a recap on the terminology.**

    I'm Knox from Community Cycles in CO and in this post, I'll walk you through the bumps I have found for the Surly Krampus.

    For any mid-drive kit, there are 2 main things you need to be looking for: chain-line and q-factor. With some builds, you can only get these so good, but the goal should be for them to be perfect.

    **The chain-line on any bike should be set up so that the middle chainring and the middle cog in the rear create a line parallel to the plane of the wheel. If you have a 1x then that's your middle, if you have a 2x then in between is your middle (you can cater to one or another depending on riding style), and if you have a 3x then it will be the middle. With a 7 speed in the back it will be 4th gear, 8 speed will be 4-5th, and a 9 speed cassette will use the 5th gear as your center. I wouldn't recommend going much higher than 9 speed to keep drivetrain replacement costs to a minimum. For mid-drives, we are referring to 1x setup.

    **The q-factor is the distance between your crank and your chain stay on both sides. If this is out greatly, it will affect your hip position and can misalign your body after lots of riding. Also, you will probably be able to feel it if one side is different than another.

    For the Krampus, we are using a BBSHD with a spindle for a 68-73mm shell powered by a 48V 11.6ah high-power (PF) battery. With the Krampus, I noticed immediately that the motor bottomed out on the yoke of the bike. On plus size, fat bikes, and some mountain bikes, the yoke is a single piece that connects the chain stays to the BB. Since the Krampus is a 29"+, the yoke is so large that without spacing the drive side of the motor, you will destroy your motor and potentially the frame by compressing it all the way without spacers. Spacers should be included in your kit, these are ONLY to be used on the DRIVE-SIDE because the Y-plate needs to contact the non-drive to prevent motor rotation. Keep in mind that if you use spacers, it will affect your chain-line, q-factor, and the amount of threads you have to tighten lock rings. For the Krampus, I had to use 4.5mm of spacers to get the motor off of the frame. You can seen in the photo below, the distance between the motor and the yoke is about 1.5mm. Same for the chainring and the yoke. If it's any closer the frame flex can cause damage to the motor and the chainring can cut into the yoke/chain-stay.
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    Since I had to use spacers, I had to figure out how to fix the already high-end leaning chain-line and the q-factor. We purchased a Luna Cycle offset chainring to help the chain-line. If Luna made a smaller size offset chainring that wrapped tighter around the motor, it would help the chain-line even more. I had to make due with their 46T, but because their teeth are so damn tall (probably to help grab the chain), I had to use their given spacer plus a small washer on all 5 bolts. If you look in the hole of the chainring below, you can barely see the extra spacer I had to use in conjunction with their given silver 3mm spacer (bad photo).
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    Also, because I had to use spacers, we could only use 1 lock ring with Loc-tite to secure the motor (tighten to 65-70Nm). I prefer using both lock-rings provided as it looks cleaner and it's nice having a backup with a motor. You can see my set up below.
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    In the photos below, you can see that the low-end chain-line is super far out. This makes grinding noises and shouldn't be operated. The second photo shows where the chain-line is straight, the chain-line caters to the high-end. Because its so far out, I opted for a 7 speed cassette to make the relative chain-line more centralized and much less noisy. This is best you can get it unless the Luna-made ring was smaller (around a 42T), just enough to clear the motor.
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    Since I made the chain-line the best it could be, I moved on to the q-factor. The first photo shows the stock crank arm set up. The second shows the offset crank arm you can order as an extra. The third photo shows the crank arm I used for the build. It's offset isn't as intense as the Luna aftermarket crank arm.
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    The stock crank arm has about an 18mm offset whereas the offset arm is around 48mm. For the Krampus I needed something in the middle. I found a left crank arm sitting around my shop that fit the bill perfectly. This arm has around 36mm offset. You can see the differences in the photo below.
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    All in all it went smoothly. The chain-line still isn't perfect, but it's the best that can be done with the bolt-on parts that are available today. The chain is noisier on the low-end but nothing nearly as bad as running an 8 speed cassette. The q-factor is perfect and the motor has no issues slipping with drive-side spacers. Enjoy the completed build photo below. Please comment. Click image for larger version

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    Attached Files
    Last edited by KnoxyBoy; 09-12-2016, 10:05 PM.

    What, no comments?

    Nice build! Thanks for sharing the details, well done. How many mile are on it now?


      Thank you for the write up on the Chain line, Q-Factor and Crank Arm Offset! Much appreciated, H20man


        My chain line on my 10 speed Sturgis Bullet is AT LEAST as wonked out as yours, but to my surprise over the last 650 miles of very steep trail riding (I have another bike for level road riding) I have yet to experience any chain drops or shifter problems. Just yesterday I checked the chain with my new Park chain stretch tool, and it still checks out fine. I also bought another ebike specific chain (should last even long I suppose) as a backup, the one I now have is the stock one that came with the bike.


          Great mod!
          How is the build holding up?