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A Progressive Fat Bike - is that even a thing?

Updated: Apr 9, 2022

Some History: I remember the first Fat Bike I saw in person (A Surly Pugsley). The year was 2011, and up until then I had viewed fat bikes solely as the domain of folks racing Iditarod - and definitely as a "mode" that existed on the fringes of two-wheeled endeavours.

I was winter trail running with a small crew that day, and got a good look at the rider and his fat bike as he rolled across the back country parking lot. The rider rolled past us, onto a snowshoe track - and off they went at a fairly good clip. I was so intrigued by this sighting that I started researching various options, and by the winter of 2013 I had procured a bike of my own - a blacked out Kona Wo.

I'm sure Kona tried their best with that bike, and it hit the market before many of their competitors did - but it was horribly heavy, had shameful geometry and came with an utterly dismal parts specification. Sort of like a beach cruiser. The bike was ghastly on trails, but - it was technically a fat bike. I enjoyed the experiences I had on it, but I definitely wanted more. Especially the ability to fit wider tires (I had the Wo setup with 5" front tire and a 3.7" rear). In those days, people really couldn't predict how popular winter trail cycling would become.

The Author aboard the Kona Wo, Circa 2013. 4.0" tire max. 70 degree HTA. 73 degree STA. Whoa is right.

In the next few years other brands began producing fat bikes in droves, as fat biking became the new "thing". Every serious bike nerd needed one and soon many offerings were available on the market. The Specialized "Fat Boy" dropped in 2014, and offered the ability to fit 26 x 5" tires - and came stock with a carbon fork. It was priced right as well. Hoo boy! I just had to upgrade.

Lake Minnewanka. 2014. The Specialized Fatboy on right. 5" rubber. carbon fork. 70.3 HTA. 73 STA. At least it was light(er) and could fit the biggest 5" tires.

The Specialized was better. Being lighter than the Wo and fitting the big Surly tires of it's day helped a lot - and I enjoyed that bike immensely. The bike started to show me what was capable on a fat bike, and moved me in the direction of an ever more aggressive and capable winter mountain bike.

In 2016 Trek stunned the fat bike faithful with the release of their Farley 9.8 and 9.6 - full carbon fat bikes paired with a brilliant parts specification. Well, I was compelled to upgrade yet again. This time I outfitted my bike with the newly offered Rockshox Bluto - a 32 millimeter stanchioned fat bike specific wallowing blunderbuss of a fork (it was a bit of a miss).

45North was offering serious tires for serious riders, studded and aggressive as all get out - and obviously I needed those too.

I was so very cutting edge (*sarcasm*).

The 2016 Trek Farley 9.6. A 69 degree HTA. Sliding dropouts. Room for a longer dropper post. Finally. a real mountain bike.
I miss you Farley 9.6. Even though you were built overseas by unethical labour, and were non-recyclable - we had some really great times together.

Ok, so maybe cutting edge is an exaggeration. The locals in the Calgary area were all evolving the sport of fat biking at a speedy pace, so what worked and what didn't was common talk on trails - in parking lots - and of course on the internet.

Next I dabbled in full-suspension fat biking, ditching my carbon Farley picking of a Trek Farley EX the following year. That bike was ultimately plagued by design issues; the shock would collapse and lose air at any temperature under -10 C (as would the suspension fork). It also could only fit a 4" wide tire, a serious impediment to winter performance. Ultimately I converted the bike to 29+ and used it as a shoulder season rig, which is where it had some utility.

The 2017 Farley EX8 suspension Fat Bike. A good idea, poorly executed. Discontinued due to identity crisis. 29+ made it (more) useful.

By 2018 I had a very good idea of what I actually wanted from a fat bike, so I ordered a custom chromoly steel bike frame from REEB cycles out of Colorado. That frame was actually the final catalyst in my journey to becoming a frame builder. I still have the bike. I love it, it is not perfect but - I love it.

I specced the frame with a slack 66 degree head tube angle, but where I messed up somewhat was I allowed REEB to set the seat tube angle. As a result I got a 70 degree seat tube angle, and it made the bike a somewhat poor climber. I have to run the seat in the forward and nose down position to compensate. Their Fat Bikes offered out these days have much more progressive geometry.

Coupled with Di2, a burly Manitou Mastodon Fork, custom Onyx hubs laced to Sun Mulefut rims - it is a mighty steed, but definitely not the final stop on the evolutionary ladder.

My mighty custom REEB Donkadonk. It is a bikepacking rig. It is also my winter shred bike. Just add and remove accessories as necessary. Is the seat angle ideal? Not really. The bottom bracket is also a bit too high. The standover is poor. Despite that, I log many rides in a year on this bike.

A Progressive Fat Bike borne from a Collaboration

You may have heard of a fellow named Reggie "Reg" Mullet, a well known Calgary MTB local. Reg has been a past President of MMBTS (Moose Mountain Bicycle Trail Society), a trail builder extraordinaire, and has held the world record for vertical meters of descent in a 24hr period. He is a great guy to ride bikes with too, with massive stoke and infectious excitement for the sport.

Six months ago Reg asked me about a progressive fat bike, and we started a conversation that eventually wound towards the following basic plan:

  • T47 bottom bracket on a 120mm wide shell

  • Room for 26 x 5 or 27.5 x 5 rear tire

  • Sliding dropouts

  • Room for a 230mm dropper post

  • Tucked rear tire

  • Low COG (similar to a Santa Cruz Tallboy, under sag)

  • Steep seat tube angle for climbing (76)

  • Slack head tube angle for descending (65.5)

  • Huge standover clearance

When we met up, Reg reported that he had never felt truly comfortable on a fat bike. He bemoaned the lack of space for a bigger dropper, the smallish cockpits, the poor standover room, the short front center, the slack seat tube angles - that essentially ALL fat bikes have (exception - Rocky Mountain Blizzard is close to what Reg specced from me, but still not quite up to true all mountain shredding). He was a great customer, very specific in his wants with great reasoning behind the various aspects.

The below rendering is exactly what Reg got, when I built him the bike over Christmas 2021.

Interesting fact. Reg's vision was more conservative than mine. I originally wanted to run a 77 degree HTA, and a 63 degree HTA. Ultimately we talked it out and he was correct, fat bikes experience different traction conditions than a regular MTB. Thanks Reg! Anyone who wants a fat bike from KRUCH from here on in, just ask for the "Reg".

On Reg's first daylight mission on the bike, aka "new bike day", I was along with my camera. I grabbed some photographs as seen below. Reg LOVES his new ride, and I'm stoked that I was able to deliver on a shared vision. This result is why I build bikes.

Hit me up if you want one of your own!


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