A recognizable situation: you pedal, the bike pulls ... and yet it feels like it is “changing gears”
Anyone riding an e-fat bike or e-bike with the Bafang H720 for the first time often notices two things. When pulling away, the support feels powerful and direct, and as soon as you speed up, the character of the drive changes. That second feeling raises questions: is this internal acceleration, when exactly does it happen, and can I influence it?
The Bafang H720 is a rear-wheel motor with a built-in automatic 2-speed system. So you don't shift gears with a lever; the motor “chooses” itself between two gears to make both pulling away and continuing cycling more comfortable.
In this article you will read about what happens technically, what you notice in practice and what conditions determine when the engine shifts.
What is the Bafang H720 and what does “automatic 2-speed” mean in normal human language?
The H720 is a hub motor for e-bikes with wide tires and higher loads, such as e-fat bikes and cargo bikes. “2-speed” means that internally there are two fixed gears: a “low” position for torque at low speed and a “high” position for a more comfortable pedaling feel at higher speed.
You can compare it to a car with two gears, but fully automatic and built into the motor housing. The motor does this to avoid two problems you encounter with many simple hub motors: a heavy, viscous feel at higher speeds or, conversely, a less convincing start at low speeds.
Why do manufacturers use such a system?
- Smoother driving away with more pulling power without the engine immediately “hitting its rev limit.”.
- Pedaling more naturally as you pace so that the support does not feel abrupt or choppy.
- More control with loading, which is especially noticeable with cargo bikes or heavy shopping.
The mechanism explained: what is in that engine that can ‘shift gears’?
An automatic 2-speed hub motor essentially contains an additional set of gears (a planetary gear) and a shifting mechanism (clutch/ratchet) that can choose between two paths. The motor rotates internally in a manner appropriate to electrical efficiency, and through the transmission, that is converted to wheel speed and torque.
With the H720, then, shifting is not a software trick that just changes the power. It involves a physical change in the gear ratio in the engine. This is also why some riders may feel a subtle moment of “transition.”.
What drives switching?
In 2-speed automatic systems, the shift logic is in practice tied to metrics such as wheel speed (speed) and load (how heavy the system is). The controller evaluates those signals and allows the engine to shift to the other internal ratio when it makes sense.
The exact design details (such as exact thresholds and the way the clutch engages) can vary by version and adjustment. Manufacturers tailor this to the handling they want to achieve.
When exactly does the Bafang H720 shift gears? An honest answer (and what to expect)
The question “at what km/h does it shift?” is understandable, but there is rarely one magic number that is always correct. In practice, a 2-speed automatic motor shifts around a speed range, and that range is affected by load and conditions.
What you usually notice: the engine stays in the low transmission during acceleration and at lower speed. As soon as you drive more steadily and the wheel speed increases, it shifts to the high transmission. When braking or under heavy load, it may downshift.
Factors affecting the switching moment
- Total load: rider, luggage, child seats or cargo bike capacity.
- Slope degree: on a climb, the engine often stays longer in the “low” ratio.
- Wind and subsoil: headwind or loose ground requires more torque and can delay shifting.
- Support mode: higher support gives faster acceleration; that can make the transition happen earlier, but load can offset it again.
- Driving Style: building up slowly versus pushing hard.
A practical directional view
Think of shifting as a bandwidth: an engine like the H720 will typically shift gears at “from acceleration to cruising speed,” and downshift at “from cruising speed to heavy work.” So that may happen more often in city traffic than on a long, steady route.
Want to test it yourself? Ride on a flat stretch of road and build up the speed gradually without varying pedaling pressure much. Notice when the pedal feel and engine response change; that's often the shifting moment you're looking for.
What do you notice as a rider: comfort, sound and pedal feel
The main effect of a 2-speed hub motor is not that you suddenly go much faster, but that the assistance feels more “logical” over a wider speed range. At low speed, you have that push to get away. At higher speeds, it feels less like the motor is past its best operating range.
Typical signals that the motor has switched
- Pedal feel changes: it may feel lighter or more consistent at the same pace.
- Engine response changes: the support can become less “jerky” and more suitable for cycling through.
- Subtle click or transition: some riders hear or feel a mechanical transition very briefly, especially with varying loads.
Why this is relevant to fatbikes and cargo bikes
Wide tires, a robust frame and often extra weight mean that you are more likely to ride in situations where a lot of torque is desired: acceleration with mass, speed bumps, turns, traffic lights, ramps and sometimes sand or cobblestones. This is exactly where a low internal transmission can make a pleasant contribution.
With a cargo bike, something else comes into play: stability and control. When the drivetrain is better “in its power” at low speed, maneuvering with a load feels calmer. That aligns with what many families and city riders look for in daily use.
Practical examples
- Stoplight road with two kids in the tub: less feeling of having to “get going” first.
- Curves in narrow streets: you more easily maintain even support without weird spikes.
- Long straights: the system looks for a ratio that makes cycling through more pleasant.
Overview table: what affects switching and what can you do?
The table below helps link the most common questions to a practical approach.
| Situation | What the engine often does | What you can do |
|---|---|---|
| Slow acceleration on flat | Stays in low ratio for a while and then switches to high | Gradual acceleration for a smooth transition |
| Hard on at traffic light | May shift gears later due to higher load | Just after taking off pedaling a little more consistently |
| Climb or bridge with loading | Holds low ratio longer | Increase cadence slightly and do not “stomp” |
| Headwind on open stretch | Switches to high possibly less quickly | Adjusting support mode for comfort |
| Slow down and turn on again | Can downshift and upshift again | Anticipate: keep light pedal pressure during deceleration |
Frequently asked questions about automatic switching
Is it bad for the engine if it shifts often in the city?
Many shifts in stop-start traffic are part of the design. An automatic 2-speed engine is designed to remain pleasant to drive precisely in changing speeds. However, it does help to avoid extreme, sudden load changes if you want as smooth a transition as possible.
Can I set the switching point myself?
With this type of system, the switching point is usually fixed in the motor/controller combination. In practice, you mainly have indirect influence through riding style, load and assistance level. If you want to know exactly how your bike is adjusted, it is wise to check the specifications of your model or ask the supplier.
Is this the same as an automatic transmission hub?
No. An automatic transmission hub sits in the bike's drivetrain (for example, in the rear hub as the gear system) and changes the pedal transmission. The H720's 2-speed is internal to the motor and changes the motor transmission toward the wheel. The purpose is similar (comfort over a longer range), but the technology is different.
How does the H720 compare to other sensors and actuators?
In many e-fat bikes, ride feel is heavily influenced by the sensor that controls the support. Some systems respond primarily to pedal rotation (rotation sensor), while others look at pedaling force (force sensor). This determines how “natural” support feels.
The 2-speed motor changes that because it also mechanically optimizes for low or higher speed. Combined with a low-maintenance drivetrain, such as a belt, you often get a quiet, consistent cycling experience.
More context on the H720 in STOER models
STOER Bikes describes the H720 and its automatic dual-speed system as part of the bike configuration on several models. You'll find this info in the brand's product specifications and background pages, including explanations of components used and low-maintenance component choices.
- STOER Bikes: background and brand story
- Overview of bicycles and configurations
- Documents and practical information
Resources: where to check general background on Bafang and hub motors?
For a general, non-brand-specific explanation of Bafang as a manufacturer, visit Wikipedia. That provides context about the brand and its product families, separate from specific tunings by bike model.
Practical tip for doubters: test on your route, not just in a parking lot
You notice the shift timing and benefit of 2-speed best in the same places you normally ride: stoplights, speed bumps, bridges and stretches with headwinds. Also consider a scenario with loading when considering a cargo bike.
Want to feel how this turns out on a STOER model with the H720 and automatic 2-speed? Then schedule a quiet test drive via the page Test ride and consciously pay attention to acceleration, cruising speed and transition moment.