Fat Bike E-Bike Build (Pugsley and Bafang Content)

(Disclaimer: GRM might earn a commission if you buy any products linked in this thread. But I paid for all of this with my own money and nobody is paying for this content.)

Back in college, I built a Pugsley from a bare frameset. Sorry for the potato quality photos--my garage was dark and my phone was a bad camera back then.

So what's a fat bike? They're common now, but a decade ago they were something that nobody had seen before: Take traditional mountain bike geometry, add giant tires, and boom it's a fat bike. They're great for sand, which we have plenty of here in Florida.

But while the fat bike is a fun novelty (and perfect for riding on the beach), it's mostly sat dormant. I'll take it out a few times a year for a laid-back trail ride, but it generally has a different attitude about riding than I do. It likes to slowly trundle along the trail, while I prefer the faster, lighter experience that my XC bike or gravel bike provides.

Then I rode a modern e-bike--a $10,000 model from Specialized--and something clicked. I thought the electric motor was pointless on a carbon mountain bike, as it removed the light and playful nature I look for. But it would be perfect for a big comfy fat bike, and I just so happened to have one sitting in the corner... time to electrify the fat bike!

Step one: Throw the bike on a stand and order parts. Fortunately my garage is bigger and my camera is better this time around, so you'll actually be able to tell what I'm doing in these photos.

And here's my parts list:

$492 Bafang BBS02 Electric Bike Kit: 
https://amzn.to/3ZjLLaU

$270 52v, 13ah Battery:
https://amzn.to/3zaIuA4

$20 gearshift sensor:
https://amzn.to/3FVNP2d

That completes the hard parts for the actual electric conversion, but I also figured I would kill myself if I didn't also upgrade the brakes. Back when I put the bike together, I ran out of money and fitted the cheapest cable disc brakes i could find. They were barely adequate without a motor, so I bought a cheap set of hydraulics.

$90 Shimano Hydraulic Brakes:
https://amzn.to/3FUBT0v

And I'm adding some new $22 grips, because the ergonomic grips on there were never comfortable on long rides:
https://amzn.to/3TPa3bV

All in, this project is a roughly $900 adventure. But remember, the goal is to beat a $10,000 bike. I'm cautiously optimistic that I'll at least get close.

And before anybody asks: Yes, it would have absolutely been more cost-effective to just buy a pre-built electric bike. The bottom of the electric fat bike market is somewhere around $1500-$2000, but this conversion should end up with a way higher quality (and more powerful) finished product. 

I wholeheartedly agree with this content. It should be fun to read.

The bottom of the market isn't a great place to be in the world of E-bikes. 

This is my Biktrix Juggernaut Ultra Duo 2. It is a beast on and off road. It has a 1000-watt mid-drive and that's a lot more power than you need. I've never run the assist level above 1. There are also problems with the 1000-watt motors breaking chains if you aren't careful about your shifting. 

Okay, let's get this out on a tray....

First up, the battery. This thing is, well, terrifying. Why? Because it's a LOT of energy wrapped in the flimsiest plastic available. I chose a 52V nominal (roughly 60v fully charged), 13ah battery. What could go wrong? The instructions also show a completely different battery.

Oh, wait, it's Grade: A. Now I'm not worried at all.

This will bolt to the frame right here, in place of a bottle cage. 

The battery weighs in at just over 9.5 lbs.

Next is the motor/controller, which is known as a BBS02. These are available in a few different widths to match your bike's bottom bracket, and I had to hunt for a 100mm wide one to match the Pugsley. Rated wattage is 750 watts, or roughly two Lance Armstrongs on drugs. A normal cyclist makes maybe 100 watts. Total weight? Just over 9.5 pounds. Add in some wiring, and the entire conversion should add just under 20 lbs to the bike.

With the "staring at it" phase of the build complete, it was time to get to it. I pulled the chain, bottom bracket and front derailleur off, then did a test fit with the motor. I was fully prepared to start machining spacers, denting tubes, etc. but instead... It bolted right on with zero modifications. Sweet!

Next, I put the little display on the bars. This also just slid right in, and every wiring connection was plug and play:

Oh, and I put the little included headlight on the fork:

Next i clipped the battery on the frame, moved the wiring far enough out of the way to not get caught on the pedals, and fired it up... And nearly sent the whole contraption flying! Even on its lowest setting, blipping the throttle was enough power to nearly tip the bike stand right over thanks to the mass of the rear wheel. This thing is going to be rowdy!

With the test run complete, it's time to neaten up the wiring, finish installing those hydraulic brakes, and go for a test ride. I'm hoping to finish everything up tonight. So far I have about four hours of real-life time invested, but that's included a lot of hanging out in the garage, tidying up, reading about other peoples conversions and listening to podcasts. I've only done maybe 30 minutes of actual work to the bike.

After seeing how good the crackies and bums get around on them, im really curious to see how good this is. It should be great.  They have basically become lightweight electric motorcycles. Most of the time i see people hauling butt on them, they also aren't pedaling. 

Good to see some fat-tire love here. My wife rides a Haibike FatSix. She LOVES it. We did the entire length of the Great Allegheny Passage and most of the C&O canal Trail in September 2021, pictured. 300 miles in 10 days. Electric fat-tire bike was perfect for the rail trails. Leaving to ride the Escalante Staircase in Utah in a few weeks...mostly on forest roads. Should be good there, too.

BTW, I got one of those fancy carbon eMTB's -- Specialized Turbo Levo Comp Carbon. The nicest mountain bike I've ever ridden and it not even close. 

--bb

Whelp, life sidetracked this project a bit but I finally finished it up this morning:

And, uh, WOW. I have no idea how fast it goes yet--I softly pedaled it to about 25mph on assist level 5 of 9--but even in shop clothes and steel-toed boots I'm hooked. Time to take it to a trail and see what it can really do!

Very cool! I remember when the Pugs initially came out the local bike shop actually had a demo day for them.  I couldn't swing for two of them (son was pretty into riding at the time, and just gettingone would not have gone over well).  He bought his own a couple years ago, a Giant I think. It started off as a winter/spring bike to ride until things dried up, but his 'main' MTB never left the basement last year.

I'm horribly old, fat and deconditioned now, but I suddenly am looking for a Pugs...

Tom Suddard said:

Rated wattage is 750 watts, or roughly two Lance Armstrongs on drugs.

*golf clap* Well said.

I've had the same sized battery, and the same motor on my Bakfiets for 3500 miles and probably 5 years. No problems at all with either, and no complaints about the power. You were smart to spring for the better chainring - it will make the setup much more robust. 

It gets up to speed really quickly on my 120+ pound bakfiets with two kids on board. I can't even imagine it on a Pugsley. 

Make sure you check the lockring often on the bottom bracket motor. The BBS02 has a habit of torquing hard enough to loosen it, even when you tighten it with a hammer. 

Very cool bike! I ride the OneSport OT05, and I prefer this type of electric bicycle with an integrated battery. I think it's fantastic!

Time for an update: I converted this bike just over a year ago...

...and rode it maybe three times total.

Why? Honestly, I'm not sure: It's fun, it's fast, it's awesome. But I have three motorcycles and two mountain bikes, so this sort of fell into an uncanny valley where I consistently chose one of the other two-wheeled machines to play with. 

So I sold it to a local mountain biker, putting some money back into the fun budget. What's my next project going to be? Perhaps I'll finally get around to building my miniature golf cart:

https://grassrootsmotorsports.com/forum/grm/i-want-to-build-a-34-scale-taylor-dunn/262016/page1/