GNG Gen2 build

[Joe T.]

I found myself here at endless-sphere.com over 3 years ago when I started looking for information on Ebikes. Since then I have built several ebikes as well as helped friends with theirs. This summer I built a bike using a GNG Gen2 kit. I am very pleased with this kit. I have built about 7 bikes this year all using this same kit. Most of these bikes are destine for rail trails and basically light duty flat riding. I test ride the bikes I build and I like to punish them to make sure they will be reliable. I have no doubt that this drive would be at home single tracking in the woods.

I decided to put my money where my mouth is. I bought a fat bike from the internet for $500 and installed a GNG Gen2. I have a few pictures of the bike I will share. The install had a few bumps like the 100mm BB but otherwise a simple bolt on like the others.

I pressed apart a bottom bracket cartridge to see what is inside. Basically a 16mm shaft and two sealed roller bearings. I grabbed a ¾” grade 8 bolt off the shelf and turned it into a new wider BB spindle. I re-used the bearings and threaded cups and created a new properly spaced BB.

The motor mount is nothing more than two flat steel plates that squeeze against the BB of the frame. The kit is for a 68mm BB and the fat bike is 100mm so I made a 40mm spacer to bridge the gap between the motor and the frame.

The kit comes with a large hose clamp to keep the motor against the down tube of the bike. It works O.K. but is a little tacky. I usually cut a piece of rubber belt ( Subaru timing belts are plentiful here) to protect the paint. On this bike I decided to support the motor a little differently. I took some 3/8 X ¼ aluminum stock I had and made a skid plate – mud guard – motor support. I then riveted some plastic sheet to keep the mud off.

Fat bikes are a bit unruly on pavement and this one is no different. In the woods and on the trails I am very impressed. I took it out today and this thing doesn’t blink an eye when it comes to the hills.

What I fix from the kit.

I made my own chain tensioner and I have yet to get the supplied bottom bracket lock ring to thread on the shell. Some I reused the original one from the bike. Others I pressed and welded the ring to the shell. That is about it.

 

[robocam]

How much did this kit cost you? How many miles have you put on the Gen 2? How did you decide upon this kit and what other kits did you consider?

I wonder if the chain tensioner should push on the chain so that more of it wraps around the motor sprocket.

...I test ride the bikes I build and I like to punish them to make sure they will be reliable. I have no doubt that this drive would be at home single tracking in the woods...

 

[Joe T.]

I personally own a GNG belt reduction with Lightning Rods updates. I have over 2000 miles on it. I have a Trek with a Luna/Bafang 750W kit on it that I have close to 100 miles on. I built it to sell and wanted to have a clean “store bought” look. I helped a friend build 2 fat bikes with Luna/BBSHD drives.

I liked the simple, clean look of the Gen2 but was concerned with the lack of support on here. I ended up building a light duty bike and decided to try the Gen2 to find out for myself.

The power of the Gen2 was impressive and unexpected. The bike has wheelie power! It was then when I decided to use this drive for more serious bikes. Most of which is covered in my opening post. The price in on GNG web site.

I tried the chain tensioner under the chain but the spacing simply doesn’t allow a good fit. Any slight run out causes an instant chain drop. The way it is in the picture has been rock solid. I think the long run to the driven sprocket allows the chain to self guide. Most of the bikes I have done use the supplied tensioner setup with no problems. I built the motor mounted tensioner in advance because I am going to test out larger reduction gears and drive gears that will block access to the stock tensioner bolt. I have had no chain skip on any chain rings.

 

[robocam]

Which GNG belt mid drive did you put 2000 miles on? The original, 2015, or 2016? I have the 2015 belt mid drive, and I have that exact crankset you have pictured in this picture, and the crankset freewheel failed within hours of using it (due to what I think is an engineering flaw), so I'm honestly surprised that you're having such good luck with it. How many miles of experience do you have with that specific crankset?

Yes, I know the price on the website is $468.80 but I was curious how much you paid for it, since $468.80 is a lot for something like that considering what's available today. Since you're after a store bought look, wouldn't a BBS make a cleaner install (no exposed chain, built-in controller)?

There's another user here that has nothing good to say about his GNG Gen2, so I guess it's good to see that you're having a good experience with it.

I personally own a GNG belt reduction with Lightning Rods updates. I have over 2000 miles on it. I have a Trek with a Luna/Bafang 750W kit on it that I have close to 100 miles on. I built it to sell and wanted to have a clean “store bought” look. I helped a friend build 2 fat bikes with Luna/BBSHD drives.

I liked the simple, clean look of the Gen2 but was concerned with the lack of support on here. I ended up building a light duty bike and decided to try the Gen2 to find out for myself.

The power of the Gen2 was impressive and unexpected. The bike has wheelie power! It was then when I decided to use this drive for more serious bikes. Most of which is covered in my opening post. The price in on GNG web site.

I tried the chain tensioner under the chain but the spacing simply doesn’t allow a good fit. Any slight run out causes an instant chain drop. The way it is in the picture has been rock solid. I think the long run to the driven sprocket allows the chain to self guide. Most of the bikes I have done use the supplied tensioner setup with no problems. I built the motor mounted tensioner in advance because I am going to test out larger reduction gears and drive gears that will block access to the stock tensioner bolt. I have had no chain skip on any chain rings.

 

[Joe T.]

I like the look of the Bafang but I don't like the function. The ones I have used have not suited my riding style. The GNG is a better fit for what I am doing plus I can juggle drive gears to alter the cadence to dial it in to me if need be. The throttle response is better in the trails.

My personal bike is the one in my avatar. I bought it in 2013 and upgraded it with LR parts after a year and about 6 belts. The LR belt has not failed. My crank set is custom made. You can see it in my build thread. THAT bike has over 2000 miles on it and the motor and controller are original. I have changed the motor bearings from salt and water issues.

The GNG freewheel in the picture seems to be working fine to this point. I don't know what has been failing on the new GNG set up. I have climbed good steep hills with every one I install.

 

[Joe T.]

I built an adapter for the GNG freewheel hub so I can use easier to get 104mm chain rings. I swapped out the 42T drive ring with a 48T. This gives the motor more advantage and lowers the cadence at the pedals. I anodized the parts red to add to other red features on the bike. This required a longer chain.

I took it out for a few rides and it is an improvement.