First build, need help and advise......

Jpac007

New Member
Hello, I just bought my first ebike (fat tire) for hunting, camping, etc. and LOVE it. Now I see there are conversion kits for non-ebikes, (I did not now this) but am excited. I have a Trek 4series mountain bike I’d like to convert for my son. Mostly off-roading. I am suffering from information OVERLOAD regarding conversions, soooo much to take in. So if you could help with what I need, that would be great. I just don’t want to spent $400-$800 and it not fit or work on my bike. I’ll need something that will last days at slow speeds as we will be on the continental divide trail. I’m thinking rear hub motor, more for ease of installing as the mid-motors look a bit complex for me to tackle. I’m looking for a “kit” that will work for me as getting several components and assembling is not in my wheelhouse. Thanks for taking the time to read this, any help is greatly appreciated.
 

Clyde

Active Member
I'm not sure the 'last for days at slow speeds' requirement is realistic unless you've got a way to recharge during the day. A really expensive, really high capacity battery on flat ground at minimum assist on a very small hub motor might get you 100 miles of range, or a little more.

I've just finished converting a mountain bike with a BBSHD mid-drive (really only slightly more involved than a hub motor install if you're using a PAS sensor on the hub motor), and I'm in the middle of converting a kickbike for my son using a 500w Bafang hub motor.

Both came as a kit with e-brake cutoffs, display, throttle, motor controller, etc. I had the mid-drive installed in an afternoon (getting the bottom bracket clear was the bottleneck there, and I ended up having my LBS help out when the tool I'd bought proved inadequate). The hub motor install took about an hour and a half due to some clearance issues, but I have yet to decide on locations for the motor controller (the mid-drive motor controller is built-in) and battery. I'm not a mechanic of any kind, but fairly practical and have some basic tools around.

I chose the mid-drive for my bike because I wanted to be able to take advantage of a 3-speed internal geared hub, which will give me the equivalent of a 16, 24, and 32t cog at the rear. I'm currently running single-speed with the stock 46t chainring and an 18t rear cog, which makes pulling away from a light a little tough, but tops out around 33 mph. I may drop down to an aluminum 42 or 40t chainring, which should more or less maintain my top speed in 3rd gear, while giving me more low gear options for torque.

For the kickbike, which has no drivetrain, the hub motor was the only game in town. I went with a geared hub motor in order to still be able to mount a rear disc brake, and because the rear wheel is a 20" and might not fit a larger direct-drive motor. It's got its limitations, as it's unaffected by gearing, but should work well in that application.

I'm only familiar with Bafang gear, for the most part, but lots of others here will have great suggestions. Good luck!
 

TimJohn

Active Member
There is so much to learn...you are asking the questions at the right place. I did two builds with front HUB geared motors, controllers, PAS assist and GRIN CycleAnalyst that took about 2 hours to get assembled. You may not reach your objectives of range ... just buy additional batteries because that's what you are going to have to do if you want "that will last for days". However from what you describe, I think mid drives are best for mountain bikes.
 

TimJohn

Active Member
Ok that’s good to know. So in my case, I can get about an honest 30 miles per charge on one of my ebikes but that’s all city riding. So in the bush, you may be able to get a few days riding then.
 

indianajo

Well-Known Member
Buy a complete kit from somebody, so everything matches up. I've used ebikeling and lunabikes. Be prepared to buy tools if you have to remove a crank to install a PAS pickup. I like front hubmotors that allow me to have 8 speeds on the rear. Rear hubmotors require a freewheel, not a cassette, and only 7 speed clusters will fit the 135 dropout. Steep grades in dirt would be a reason not to buy a front hubmotor. You'll need a drill hacksaw vise and safety glasses to make brackets etc. If the slot in the fork doesn't match the motor shaft (mine didn't) you can grind out the fork slot with a 3" wheel on a mandrel. No suspension forks, aluminum carbon or plastic forks with front hub motors.
Best option for long range no AC available trips is a suitcase generator. Noisy but you don't have to camp next to the generator as you have to be near a blatting motor on a gas bike. Multiple batteries all deteriorate whether used daily or once a week, so that is an expensive option after a year or two when all the batteries expire.
with 77 hills on my commute I got about a 30 mile range out of 17.5 ah battery on the ebikeling hubmotor. Now that I've worn it out (~4000 miles) I changed to a MAC12 hubmotor which seems to be more efficient. I use from 52.5 to 48.1 v on my 30 mile commute now, about 2/3 charge. The mac12 from luna the clutch shudders & shakes the fork when it engages sometimes, not suitable for cadance PAS use. (I use a throttle exclusively).
 
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AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
For off road, I would not recommend a direct drive rear hub under any conditions, so that may help eliminate some choices. For me, the call would be a gear driven rear hub or a mid drive. For off road only in the area you mention, I would most likely go with a mid drive.