So I finally put the finishing touches on the Big Boy fatbike proto this past weekend. Albeit sans paint which is the final “finishing touch” on the build but for all intense purposes, it’s finished. I was hoping to get this finished for this past winter season but finances, timing and luck didn’t play out in my favor. The weather did in some ways (not as cold/snow so I was able to continue working on the shop well into the winter) but in other ways, did not cooperate. Not to fear though-I’ll be riding this and putting it through it’s paces here on the local trails all spring, summer and into/through the winter. I’m most curious about the snow in fact as that is what this build was primarily built for. I do realize that many are enjoying these off snow as well as rock crawlers. There is a roller behind the shop that is not too big not too small and of course, I headed right for it. No problem-the Big Boy ate it up and spit it right out.

One thing you notice right away on dirt is the traction and the gobs of it that the Surly Nate offers. The sheer size of these tires makes you shake your head with a giant smile. They’re truly something to admire. The second thing of note is the bikes ‘sure footed’ line choice. Bring it up to speed and it holds it’s line well. The audible hum/whirl of the tires is wonderful.

Build wise, I attempted to give the most tire clearance while balancing other attributes. I have noticed other builds being on the tight side sometimes – keep in mind this is with a 70mm rim. At the time of it’s conception, that was the largest rim on the market. But much has happened in a short time period with wider rims so I’d be excited to see this monster with a 100mm rim in the rear. I’ll be building up a matching front wheel but will most likely follow my current vein of thought with a wider front rim than the rear wheel – so most likely I’ll be building with a Speedway 90mm front / Paul Whub 135mm hub setup. More on that at a later date.

Setting up the drivetrain was a lot of back and forth as you can imagine with little tweaks here and there to get a good balance of chain clearance, crank spacing, chainring/chainstay clearance (I’ve never liked when those suckers get too close to the stays…) and proper chain guide setup. The Phil Wood 100mm bottom bracket is very well made and offers lots of adjustability. I went with a 150mm spindle length as I just wanted to make sure I had enough room to play with. So there was some back and forth as I mentioned to get things dialed in. Once setup, the modified e13 TR guide works like it should. I like using the TR or the LG1+ as it isolates all of the separate adjustments and makes for an easier time managing all the interfaces.

The build is a starting point to test out concepts and see what wheel size coupled with geometry choices renders. Kind of a control or base line as this is my first Fat Bike Build. The measurements are as follows:

70.5* Head tube angle
73* Seat tube angle (radius seat tube)
23″ Top tube
12.375″ Bottom bracket height
16.5″ Chainstay length
44mm Head Tube

I’ll report back in once I’ve had a chance to rip some more lines with this and take it out for some longer outings on well known loops. Very excited with how this has turned out. More soon…