When it comes to electric bikes, hub motors dominate the market. However, some people are also opting for a mid-drive motor. Rather than having a motor in your wheel, mid-drive systems power your crank, allowing the torque produced by the electric motor to run through your gears.
The main advantages of a mid-drive system are:
- Lower and more centralized center of gravity.
- Ability to use power through gears
- Added wait is “sprung weight” it can be protected through bicycle suspension.
I recently got my hands on the 750W 48V version of the Bafang mid-drive system and installed it on an ORBEA URBAN 20 bicycle. The following are my impressions of the system.
Installing the mid-drive system was not a difficult task but it was time consuming and required some specialty tools. Unlike regular hub conversions you will need to remove the bottom bracket. However, the rest of the process is fairly straightforward. I’m still not 100% sold on the way the motor is fastened to the frame, it’s not going to fall out but it has some potential to rotate if the fastening plates vibrate loose. As long as you have a bottom bracket removal tool and some other basic tools, installation could be performed by an amateur mechanic.
The Bafang system I was used was the 48V 750W version, it’s also available in 36V 250W, which is the legal limit in many countries for on road riding. The motor itself is rated for 750W however I suspect it could comfortably output more than that using a higher rated controller . The high voltage coupled with the 25A controller will allow for high speed if the right gears are used.
To control it, you have 3 levels of pedal assist and a throttle. A readout provides you with some basic information such as speed and trip distance. As you can see, all this equipment can get a bit cluttered. The kit also comes with electric brakes, these are necessary for any pedal assist system but sadly their quality is a little low but still functional. You may be required to find and purchase better brake levers if you wanted better braking or have hydraulic brakes as they have an electrical cut off signal that gets sent to the motor when the brakes are applied. This is needed with a pedal assist system to cut off the motor. They are not essential if the kit is throttle only as releasing the throttle stops motor power.
I took it for a 25km ride over a rough dirt path. My usual ride is a very upright 36V 200W hub motor single speed, so the increased power was quite noticeable. It cruised up to about 43km/h with moderate pedalling and when I pedalled as hard as I could with a slight tail wind I reached 54km/h. It was exciting to see how fast this thing could really go but it is dangerous at this speed. Even at these speeds, the bike felt fairly stable partially due to the weight being very low and centralized.
I have never been a fan of pedal assist so this system was not so comfortable to me. I prefer throttle only as I find I can regulate desired pedal input and motor input more finely. I often found myself caught in a juggling act between controlling the throttle, changing gears, selecting the right assist level and trying to pedal at a comfortable pace. Over the next few days I found myself getting better at it but only through a minimalist approach. What worked best for me was picking an assist level depending on the quality of the path, and then balancing the throttle and pedalling as needed. Yes, the system comes with both throttle and pedal assist sensor.
On the 48V version, I would like to see a larger crank. I was hoping I would be able to get use out of all my gears but I found myself stuck in the top gear and still frantically spinning my legs. This system uses its own style of cranks so to increase the number of teeth you will likely need something custom made. A larger crank option would really improve the versatility and the top speed.
It was certainly nice to have all that power at your disposal but it would be too dangerous on the road – and illegal. There is nothing stopping you from cruising at a comfortable 35km/h on the middle assist setting. I believe a 36V 250W version with only throttle control would be a safer system..
The BAFANG 48V 750W mid-drive kit is certainly a very well designed and constructed alternative to hub motors. While the price is more expensive than hub motors it does have its advantages. More moving parts and a slightly more complex system are its disadvantages. It could find a niche on dual suspension mountain bikes, where the high powered mid-drive will be more useful and protected in comparison to hub systems. The ability to use the gears is only minimal as efficiency losses through gears likely match any gains. Hub motors have an electrical gearing in a way by opening a voltage with the throttle. There is a finite speed range and if you are within this range on either system then using gears is not a particular advantage. Perhaps only if you wanted greater torque to pull a heavy load up a steep hill you may find a significant advantage with a crank driven system but electrical motors all have high levels of torque so any hub motor will greatly assist in any case.
- A simpler option without pedal assist.
- A larger default chain ring or at least the option to get a larger one.
- A different mounting on the bottom bracket.
- Testing one out and deciding for yourself which system you prefer.