mg1970 said:
Hello. New to this board but am interested in converting my Giant Sedona DX to electric. Done some research and it looks like a rear hub motor is best for me. It currently has disc brakes, and from what I've read is that you do away with the rear disc when doing this swap? It also has the twist mechanism on each side of the handlebar for switching gears. Can anyone recommend a nice setup? I'm guessing at least 36v and 500w. I'd like a top speed of around 20mph with a 200-220lb rider. I also have a rear rack that I use with side bags at time. The top of this should be free for the spot for the battery install.
Appreciate all help! I wanted an electric bike for a long time, and then realized i could just convert my bike that i have. I'm fairly mechanically inclined so I may just have to pick up some tools at most.
You can keep your rear disc brakes with some rear hub motors, not all. I'd want to keep the disc brakes, so pick a motor that allows that. For minimal disruption of your shifters use a compact thumb throttle without any battery voltage LEDs. I'd mount it on the right side, between grip shifter and brake. You also need to pick either freewheel or freehub version of rear motor, to match your existing gears/shifters on your Sedona. If you have more than 7 rear gears or have a cassette gearset (likely you do), you need the freehub (cassette) version.
There are so many choices of motors that it's confusing. What voltage? Geared or non geared? Wattage? Realizing that people have strong and differing opinions on what is "best", I'll just share my thoughts.
For a target 20mph bike, either a geared or non-geared motor will serve. The geared motor will go much better on hills or into headwinds, and will make more efficient use of the battery energy. Non-geared motors tend to be more silent and more reliable, while costing less. You can buy non geared hub motors on ebay or amazon for cheap. In my opinion, they are not the best solution, but many people love them, so who am I to judge?
I'm a fan of geared motors because they tend to perform better on hills and into headwinds, and are more efficient. There are several geared motors that are popular in this forum.
The so called Q100CST is a very good 36v 350W rear motor that has a cassette freehub and is compatible with disc brakes. It has a 12:1 gear reduction, so is very efficient but has limited top speed. Performance is underwhelming, but it's tiny and stealthy, so quite popular.
https://bmsbattery.com/ebike-kit/651-q100c-cst-36v350w-32-hole-rear-driving-hub-motor-ebike-kit.html
Another candidate is the Q128C, a stronger 36v 500w motor with freehub, disc brake support and more power.
https://bmsbattery.com/ebike-kit/768-q128c-135mm-500w-rear-driving-ebike-hub-motor-ebike-kit.html
Either of the above comes in 201RPM and 328RPM winding versions, and you probably want the 201RPM one for your wheel size. It is possible to run both of these on 48v for higher top speed and torque, but there is some risk of overload and burnout on long uphills.
Bafang makes a well regarded 36v 500w CST motor that is popular. It costs more, I suppose for the brand name. It is a great motor too.
https://bmsbattery.com/ebike-kit/492-bafang-36v500w-cst-rear-driving-hub-motor-ebike-kit.html
There are higher performing geared hub motors from BMC and MAC that cost much more, but for your 20MPH target they are probably overkill. These are superb motors, just way more than you need. There is a very interesting 2 speed Xiongda motor that gives great performance on flats and hills thanks to its dual speeds, but... it has a problem. If you roll it backwards, it can freeze up internally and damage internal parts. Still, if you can manage not to roll backwards, ever, this is a very good motor to consider. I hope they are working on some sort of mechanical interlock so that this lockup won't happen, but for now, the motor has this quirk to be aware of.
Freight cost will be high for these motors, above $100. I suggest that you buy the bare motor and have it mounted on your rim here, because the Chinese wheel builds are of terribly poor quality and a waste of freight cost. Save the freight and pay a trusted technician to do it right, you'll come out ahead.
