Some of the most refined electric bikes on the market are mid drives. And until recently, if you wanted a mid drive electric bike you were limited to buying an under-powered and overly-priced 250-watt Euro electric bike. Or…if you wanted a powerful bike, your only choices then were a $10,000 plus USA bike (like the Optibike or the Hanebrink). Recently, several notable mid drive kits have come onto the market which allows someone on a budget to build a mid drive electric conversion that’s even more powerful than the factory mid drives.
Suddenly electric bike builders have a lot of choices between putting together a hub motor E-bike, or a mid drive…which to choose?
Benefits of a mid drive over a hub motor
1. Climbs steep hills MUCH better than a hub motor. There are videos of mid drives climbing stairs…(a feat nearly impossible to do on a hub motor electric bike).
2. Places the weight of the motor low and centralized in the frame (instead of a heavy hub in the rear wheel) which means a better balanced feel.
3. The motor can use the bikes gears, so the RPMs stay up in it’s efficient range = More range per battery-Ah.
4. Keeping the motor in it’s best RPM range means lower peak-amps drawn from the battery.
5. Giving the motor some gears to use, also means you can get a broader range of performance from a smaller and lighter motor.
6. Easy to change a flat tire with no hub motor.
7. No more broken spokes from hitting a pothole with a heavy hub motor in the wheel.
Drawbacks of a mid drive:
1. Often more expensive than a simple hub-motor.
2. Some mid-drives are noisier than a hub, a direct-drive hub with a sinewave controller is especially quiet.
3. Mid-drive kits are more complex to install than a simple hub.
4. Shifting a mid drive electric bike can be a real pain. With a hub motor bike, the only reason to use gears is to get the right pedal cadence which usually means just staying in high gear.
5. Mid drives are generally not as well suited for flat land street commuting as hub motor bikes.
6. Mid drives are not as stealthy as most hub motor bikes.
7. If you want a super powerful electric bike (over 2000 watts) you have better and more reliable options from hub motor kits.
8. Mid drives have more moving parts and therefore tend to be less reliable than most hub motor kits.
1. Bafang BBS02 750W
Our number one pick for a mid drive right now is the 48V Bafang BBS02, and for all the details, see our article, here. First of all, it can easily be installed on over 90% of the common frames available. The installation is simple enough that any average cyclist who is capable of fixing a bicycles flat tire…can install this drive by themselves.
Second, the 1,000W power range (when controller is unrestricted), and small size are fantastic for most potential E-bikers. Lastly, the big surprise about this drive is that it is so quiet! Also, the 500W/25A unit runs on a more affordable 36V battery for E-bikers who don’t have extreme hills.
2. GNG 1,000W
The GNG catalog lists this kit as the “450W brushless“. The second mid-drive on our list, is also a kit that can be added to just about any bicycle frame that you like (maybe 90% of them?). See our article on this awesome drive, here.
I feel this motor is a better pick for off-road compared to the BBS02 (even if you are happy with only 750W). This is because the GNG has more copper mass, and it sheds heat well, so it can take more power for longer. We will be getting our hands on a third-party upgrade kit that fixes all of the weaknesses of the GNG next month (look for our review soon).
This kit has also been run at 72V X 30A = 2,200W/3-HP (with a different controller), but be aware that this level of power requires a swap to a chain primary reduction, or a wider belt. Also, the GNG allows for a stronger crankset to be swapped-in for riders who like radical jumps without bending the spindle (the BBS02 crankset cannot be upgraded).
Because of the weaknesses of many of the stock parts, we can only recommend this kit at 36V, and the seller will swap-in a 36V controller at no extra charge.
This new kit uses the same motor as the GNG. It also uses the same basic configuration, with a quiet belted primary reduction in the high-RPM half of the drive, and a narrow and strong chain in the lower-RPM half of the drive.
Although the motor is the same, every part of this drive is very strong and uses the highest quality components, including a 25mm wide primary reduction belt, instead of the GNG’s 15mm wide, and…a #219 kart chain for the secondary, which is rated for over 20-HP (15,000W). By moving the motor-freewheel from the right side, over to the large primary driven pulley on the left, the reduction has been improved to 33:1 (compared to the original GNG reduction of only 21:1).
This kit comes stock with two chainrings, a 32T and a 48T. This kit has been run at 48V and 72V, the motor runs cool at 30A, and gets warm at 40A. Using 72V X 40A =2,800W, and this is the most power that should be run through the bikes gears. More power than this and you should run a chain directly from the motor to the rear wheel, or…use a large hub motor.
3. GNG Gen-2
This kit is a converted geared hub-motor that is listed in the GNG catalog as a 36V/350W, or…as a 48V/400W. Its a great choice for a street commuter, see the details in our article about this drive, here. It’s just as easy to install as the BBS02, and..although it has less power capability than the BBS02, it also costs less. It makes the same amount of gear noise as any common geared hub-motor.
Cyclone is one of the earliest producers of mid-drives, they are from hilly Taiwan. Although this looks like a simple drive set up, the Cyclone mid drive is actually a cylindrical Headway motor attached to a planetary gear-box, providing 10:1 reduction, attached to a double freewheel. Although the steel gears of the reduction are noisier than the GNG or BBS02, they are fully enclosed to protect them from dirt.
If you buy one of these kits I strongly suggest you spend the extra money and select a kit that’s big enough (650W or larger) that it uses an external controller. Even if you only need a lower power level, the high powered motor will be more reliable than its smaller Cyclone counterparts. This is because the lower-powered kits have the heat of the controller and motor inside the same housing. Read this entire ES forum thread before buying…it’s a great buyers guide to the Cyclone.
These guys (Applied Future Technologies) are in Australia, and although they use the same motor and geared reduction as Cyclone, the rest of the kit parts are heavy duty and this fixes many of the complaints from Cyclone users. The distinctive added fins help the Headway motor shed heat much faster.
The EGO kit is from Germany, and even though the European Union (EU) has a 250W street E-bike power limit, the German off-road E-bike scene is very dynamic, with lots of exciting developments. Read the details of this kit in our article, here. It uses the same motor and geared reduction that made Cyclone famous.
Formerly known as the “Gruber Assist“, it is the ultra-stealthy drive that has the motor hidden inside the seat-tube of your bike. You can read our article about the Vivax Assist here. This system provided a mild 100-200 watt boost and its only visible feature is a red button that is mounted somewhere on the handlebars. The power assist is smooth and quiet. The Vivax kit is not available in the United States as of yet, and it can only be added to a limited number of frames, so do your homework before ordering it.
The stokemonkey is only for long cargobikes like the Yuba Mundo, Xtracycle Edgerunner, and Surly Big Dummy, but…if you actually haul cargo, this drive absolutely conquers hills when you are fully loaded. They are still available in the classic edition (where the pedals turn when the motor is running) but now…they also have a freewheeling crank option. This system has recently been upgraded, and is now sold by ebikes.ca
10. Urban Commuter M-Drive
This awesome drive is also designed for the Yuba Mundo, Xtracycle Edgerunner, and Surly Big Dummy. It performs exceptionally well on steep hills while pulling heavy cargo.
11. Sunstar SO3+
I haven’t been able to find a picture of the inside of the Sunstar SO3+ drive, but it appears to have only a single reduction (compared to the similarly-sized BBS02, which has a dual reduction, allowing higher motor-RPMs). This may have been adequate for the 250W power-limited EU market but the design ignores a large 500W/750W market in North America.
The TCM drive is hard to find any information about it. I finally found it as the optional mid drive system on “Whoosh Sport CD” in the United Kingdom. It also appears to have a single reduction.
This kit is from France and is available in the European Union. (Thanks to Carva from pedelecforum.de for the link)
14. MXUS / BTN
This drive is new and is VERY similar to the recently popular Bafang BBS02. This pic was taken at the April 2014 bicycle show in Shanghai, China. Pic thanks to ES member d8veh. On Alibaba, these have been seen being sold under the “BTN” label (Back To Nature). Thanks to the German pedelecforum.de member “airbox” for the link. Danke Schoen!
This is a late addition thanks to a posted link from Forum member Gob33 from our friends at the French electric bike website Cyclurba.fr
The Xing mid drive construction is similar to the famous Cyclone, with a planetary geared reduction between the motor and the output sprocket. The motor looks like it might be the 400W MAC/Kollmorgen used by Currie, and it is rated at 370W by Xing at 24V (which would equal a 16A controller) and the battery is listed as a Lithium-Ion with 15-Ah.
No information yet, other than this kit uses 24V and is from Europe, so it is likely a 250W system.
This company is from Italy. They have 250W, 500W, and 750W versions, and since they can be run at 48V or 72V, the amps should be very low. This drive should run very quietly.
If you like the idea of a mid-drive system, but you don’t want to install a kit, check out our article on factory integrated mid drives, here.
Written by Eric and Ron, originally published July 2012, updated January 2014