I have fiddled with the Luna 30T Mighty Mini, 40T, 42T and stock Bafang 46T chain ring. The Bafang 46T will not hold the chain consistently. The 42T is where I am sticking. Coupled with the 14-28 you can go anywhere and the stock freewheel gears seems really durable. The Luna 42T Chain line has a perfect off-set. (see pics) The 30 and the 40 had enough of an angle to cause the gears to ghost shift and grind and chatter.
I've been running the 42T with the stock 14-28 Mongoose Freewheel and it works perfectly. Comfortable top speed is about 18-20 MPH. 21-25mph, I am pedaling quickly but the motor is really spinning where it should be. I have my speed limited to 25MPH as I do not fancy dying on the road. I avoid roads and traffic as best I can.
I've got the DNP 11-34 Freewheel from Amazon that I tried earlier with the 30, 40, and 46 chainring, but I have not tried it with the 42T yet. Since the chain-line was previously less than ideal and I was getting ghost-shifting, I tried shifting the DNP 11-34 freewheel outwards with a 3mm spacer (upon advice from my local LBS) and used the 40T chainring. The gear setup for speed (11T) and climbing (34T)was excellent but I managed to completely strip the threads on the hub while climbing a 45 degree hill. Turns out losing 3MM of threads on the hub was critical under so much power. So I figured i would order a Cassette-type hub to replace the freewheel hub. No such luck. There are no fat bike cassette hubs that will fit that bike (190MM) and rim with 36 spokes in the US at this time. They are all 32 spokes. So I managed to call Pacific Cycle, the distributor for Mongoose and they shipped an entire back wheel and hub for $39.00!
So now I am running the Luna 42T with the stock 14-28 freewheel and it works great. Totally satisfied.
But.... in my never ending quest to improve upon my project, I've ordered a Shimano Type 36 spoke cassette hub from AliExpress which should be here in a week. Now that I have a near perfect chain-line, I want to try a 10/11 speed SRAM/Shimano 11-42 or 11-46 rear cassette and upgrade from the Tourney Derailleur and shifter to a higher quality.
This bike build by the way is a monstrous beast! There really is no place I cannot go, and I get a lot of looks and compliments.
Let me know if you need any help on the install ~Tom
Tom@WashDC building same bike would love to pick your brain about chainrings and gearing, can I call or text you?
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