BBSO2 Fat tire bike build


Active member
Local time
2:35 PM
Oct 22, 2022
I finished the BBSO2 Growler Fat tire bike build three weeks ago and thought I would share how it went and some pictures.

I used the easy install fat bike modification kit for Bafang BBSO2 from California Ebikes and a BBSO2 motor that was used to build my first e-bike but I never ride since I built my Felt Full suspension. I am also using a battery that I already had so all I had to buy was the bike, this kit, and a few miscellaneous spacers, nuts and bolts.

The kit went together easy enough. You need this tool from Leekie which was pricy $55! I would have just made a tool out of a piece of tubing but I wanted to get it built asap.

I put it together following this video
My BBSO2 was slightly different than the one in the video but I just put the parts in order and took some pictures as I was disassembling to make sure I put it back together correctly. I only have a small hydraulic press that wouldn't open up enough to press it together so I supported it on my work bench and carefully just taped it together with a hammer being careful to get it straight.

The first time I put it together just like he does in the video but when I mounted it in the bikes BB shell tightening down the retaining ring was pulling the extension back apart. I took it back apart using the BB shell and spacers to pull the extension back out of the motor assembly and then put it back together using red Loctite 271 and let it cure for 24 hours. I reinstalled and tightened it up and it didn't come apart. Red Loctite is pretty serious stuff requiring 500 degrees heat to break loose so I don't think it will ever come apart now.

I don't know if this is the same width as a BBSHD 120mm motor or not since I don't have one to compare it to. It fits perfectly in the 100mm BB shell with a 5mm spacer on the right side and none on the other side. There would be room for 10mm of spacers total so not really a 120mm motor I think. I then used 2, 1mm spacers under the Leekie 40 tooth chainring so the motor is In as close as possible for the best crank/pedal position, and as close as possible chain ring position. The chain alignment is right where I want it for using the lower gears. It is perfectly aligned in 4th gear so works even on the 42t 1st gear. It works with the 4.6 tires I have on right now but the chain might be touching the tire with 5" tires.

This bike is so much fun! I love the low slow gearing, great for riding up our steep county road with our dog.


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It's actually in fifth gear in the second picture but it's pretty much perfect in either fourth or fifth, hard to tell exactly but the chain is in closer than it was before I did this conversion. the Race Face crank set had 5mm of spacers on the right side and 2.5 on the left.

I have the Bafang cranks on it right now and with them the pedal placement is almost perfect side to side but I will be putting my red Kookas on as they are much better cranks and for more bling!