With lots of competing information out there, it can be hard to sort out what sort of ebike motor system might best fit your needs.
Luckily, we are a brand making quality ebikes with both mid-drive and rear hub motors; so we’re well positioned to give you some unvarnished pros and cons of both systems. As for front-drive motors, we're concerned that they can be dangerous, as low-quality software can lead to a front wheel applying torque as you turn or ride across areas with low traction; a situation that can lead to loss of control and dangerous crashes.
But first, a note that motors are only one factor contributing to the ride feel and performance of an electric bike. The quality of the controller, firmware and software are also key! They interpret the input from onboard and external sensors – like torque and cadence sensors – driving the motor according to pre-set parameters along with rider-selected assistance levels. Even the best motors can seem jumpy or rough if the power control system isn’t well-designed. High-quality control systems like those from Acer used across our ebike line deliver the most natural ride feel and power, no matter what motor they are connected to.
Now to examine some of the most important benefits that these motor systems provide to riders:
Rear hub motors win the affordability prize, with good quality systems being available on bikes from around $1000 on up. With more complex construction, more sensors and (of course) dedicated frame designs, quality mid-drive motors are not found on many ebikes under $2000, making them out of reach for lots of riders looking at entry-level ebikes.
Wattage is important, but don’t forget about the torque output of the motor system on the ebike you’re considering. There are plenty of rear hub motors with major wattage output in the 500-750 watt range that only output a nominal 50-60Nm of torque. Compare that to most 250w mid-drives where 60-80nm of torque is commonly on tap. If you live somewhere hilly, or have lots of stop-start riding on your routes you should consider that mid-drive motors will be easier to ride in these conditions. *Also, note that motors over 750w (1hp) are not ebike legal in most US localities. If you live somewhere extremely hilly, you probably need a high-end hub motor or mid-drive as low-end "direct drive" hub motors may not provide you with the torque needed to climb steep hills.
The natural and powerful boost available from mid-drive motors with torque sensors is their primary performance edge over hub motors. Factor in generally higher torque outputs for faster acceleration, weight nicely balanced in the center of the bike and you can see why most ebike enthusiasts enjoy mid-drive motor performance.
It’s pretty much a tie here between motor types. We selected our Acer and MPF motors because they are built for durability. We chose to focus on longevity as we’ve seen plenty of reports of failure in lower weight and less expensive motors of both hub and mid-drive types. We’d rather offer a better unit and a 3-year warranty than save a couple hundred grams! All in all, the key to minimizing system maintenance is to ride lightly. On many systems; including ours, the motor outputs peak assistance when you’re pedaling between 80-100rpm, so keep up your cadence and use use the assist function like a gear changer to cycle through different levels of boost from 1-4 (or 5) as you build speed, and you’ll reap the rewards with the best longevity and lowest maintenance for your entire powertrain from motor to belt and gears.
We see the upsides of each style of motor and have models that utilize both types. Everyone’s transportation needs differ, but we have a couple recommendations to help you on your way now that you have a better grasp of the basics:
If you know you'll be pulling cargo or scaling hills you'd probably enjoy the extra torque in the mid-drive motor. But if you're looking for the simplest solution to get around, the hub motor is for you.
Vvolt Ebike motors By the Numbers
Acer/Xplova Rear Hub Motor (Alpha + Alpha S models)
- 350W nomimal output
- 45Nm max torque
- Geared output (not direct drive)
- Sensors - onboard speed and temperature, external cadence sensor
MPF Drive for Acer (Proxima and Sirius models)
- 250W nominal output and up to 550 peak output
- 80Nm max torque
- Full metal gearing
- Self-lubricating via internal oil bath
- Compatible with Class 3 controller (28mph top assisted speed)
- Sensors - onboard torque, speed, cadence, and temperature