I’ve decided to do a less traditional fat bike “build.” I’m using my Pugsley Necromancer as the base. Most of the parts will still be used, but modified. I love this bike. I’ve always been a fan of steel bikes. They’re flexy, more forgiving, and the tubing has a memory. The frames will flex, and always return to their original position. And the frame geometry is perfect for all seasons of riding. This is my only bike, so I use it in the spring and summer, fall and winter. The Necro had a Shimano Deore long cage 9 speed derailleur on it. I like to jump my fat bike and I’ve been dumping the chain regularly. I also need some meatier tires for winter.
The Necro awaiting its’ new parts
I’m keeping my wheels the same. Rolling Daryls laced to Phil hubs. Why Phil? Why not? Phil Wood makes amazing products. Not doing anything with the frame or fork, they’re amazing the way they are. I love the bb7 brakes, they work well in all conditions and are far less expensive to fix if anything goes wrong.
I am a fan of a 9spd drivetrain. The cassettes are spaced wider so they shed debris well and I think they wear longer. It’s also a little more forgiving in the shifting. With a 10spd system I’ve found everything has to be adjusted perfectly for shifting to work well. The chains are also narrower, which means they generally wear out faster and are more prone to breaking. Case in point: Iceman this year. Not to mention that replacing a 9spd drivetrain is far less expensive than a 10spd. The thing that’s missing is a 9spd derailleur with a clutch, which should help me keep my chain in a jump. No one makes one. After some research and calculations, I think I’ve found a solution.
Notice the wide spacing and awesome-bombproof Phil hub.
My plan is to use a 10spd Shimano SLX rear derailleur with a clutch, and a 9spd SRAM x9 rear shifter. I’m going to use a spacer to raise the pinch bolt on the rear derailleur, which changes the pull ratio. SRAM uses a 1:1 ratio and Shimano uses a 2:1 ratio. This makes it so that you really can’t mix and match the two brands because the length of the cable pull between shifts is different. By using a spacer on the rear derailleur, it should change the ratio of the cable pull, thus allowing me to use a Shimano clutched derailleur with a SRAM shifter. I’m also going to run an X9 crankset with a Wolf tooth direct mount chainring. The X9 cranks are great. They are stiff, have a spiderless mounting system and they come with a new bb at a reasonable price. They’re pretty light too, not that I really care about that.
The X9 shifter I originally intended to use.
I used a SRAM 9spd shifter that I already had. They no longer make X9 9spd shifters. You’d either have to go with an X5 ($28) or an X0 ($134) 9spd shifter if you wanted to go with a trigger shifter. A lot of people are going with the grip shift shifter on their fat bikes lately. They have fewer moving parts internally, which makes them generally last longer than a trigger shifter. They do make X9 grip shift shifters still ($41). The main thing you need is a SRAM ESP/1:1 9spd rear shifter. I decided to try an old X7 grip shift shifter. I like the idea of being able to dump all the gears if I ever need to. There are some tight, technical trails around GR that would be perfect for this setup. Being able to go from 1 to 9 in one quick motion is pretty cool.
I then installed the cranks. There are now a bunch of different manufacturers that are offering fat bike cranks. The Surly cranks don’t really give you the option of running a single ring up front. They also don’t make a narrow wide chainring. The narrow wide chainring helps prevent the chain from falling off the front, it also reduces flex and allows me to run smaller than a 30t chainring.
X9 Crank with Spiderless Wolf Tooth ring.
I went with a Shimano SLX 10spd rear derailleur ($79.99). After I mounted the derailleur, I installed the 6mm spacer between the cable mounting surface on the derailleur arm and the pinch bolt. This, in turn, raises the cable 6mm, and pushes it out slightly. What this does is change the distance that the cable pulls. SRAM uses a ratio of 1:1, while Shimano uses a 2:1 ratio. This is why you normally can’t mix the 2 brands together. The distance that the cable pulls is different between each shift. I then adjusted the derailleur as normal. It shifts perfectly like they were meant to work together.
Special touches that only the friendliest of machinists include.
Custom made block (thanks LB)
This is awesome! I get to keep the 9spd, and I get a clutched derailleur. This prevents the chain from dropping off the front chainring. I could always get the chain to drop on a traditional, un-clutched rear derailleur if the conditions were rough enough. So far, I haven’t had any issue with the chain dropping. This makes me very happy. Also, I actually love the grip shifter. I haven’t had one on any of my bikes and I’ve always been skeptical. You usually only ever see them on entry level bikes. I love that I have the ability to shift through more than two gears in one quick motion. I don’t have to click multiple times to run through the gears. Sometimes it’s the little things. Speaking of shifting, it’s on point! With the new spacer added to the rear derailleur to modify cable pull, I have zero issues with shifting. It’s perfect, every time. Shifting is nice and smooth; there’s no hesitation or jumping. I kept the 11-32 gearing with a 30t front chainring, and haven’t had any issues. When I do need to replace the cassette, I’ll probably go to an 11-34 or a 12-36 to get a little lower gearing. It’s easy and effective. It’s also awesome knowing that when I need to replace a chain, I can replace it with a tried and true SRAM PC951 chain for only $24.99 and a SRAM PG970 ($48) or a Shimano XT ($79.99) cassette. So I can replace an entire 9spd drivetrain for less than $100 with high quality parts, versus 10spd, where I’ll easily spend $50 more for the comparable parts. Oh, and I forgot to mention the Surly Nate 120 TPI tires I installed, awesome traction – I’m sure I’ll appreciate that more once it snows again.