1. Introduction
This manual provides essential information for the installation, operation, and maintenance of your Bafang 36V 250W Cassette Rear Hub Motor (Model: RM G120.250.DC). This rear-drive motor, with a rated power of 250W, a reduction ratio of 1:4.42, and a maximum torque of 32 N.m, delivers efficient power for electric bicycles. Its robust and efficient design enhances riding comfort, making it suitable for touring bikes, commuter bikes, and mountain bikes.
2. Package Contents
Please verify that all items are present in your package:
- 1 x Bafang RM G120.250.DC 36V 250W Cassette Rear Hub Motor
- 1 x 800mm Motor Cable
3. Specifications
| Category | Parameter | Value |
|---|---|---|
| Core Data | Position | Rear Motor |
| Motor Type | Brushless Gear Hub Motor | |
| Construction | Gear drive | |
| Rated Voltage (DCV) | 36V | |
| Rated Power (W) | 250W | |
| RPM (n0/nT) | 290 / 255 | |
| Max Torque | 32 N.m | |
| Efficiency (%) | ≥80% | |
| Color | Black | |
| Operating Temperature | -20 - 45°C | |
| Mounting Parameters | Brake Type | Disc Brake |
| Installation Width (OLD) | 135mm | |
| Max. Housing Diameter | 136mm | |
| Cabling Route | Through shaft, Right | |
| Cable Length | 800mm (250 G9.1) | |
| Freewheel Compatibility | 7S-9S Cassette | |
| Tests & Certifications | IP Rating | IP X5 |
| Certifications | CE, ROHS | |
| Salt Spray Test Standard | 96h | |
| Further Specifications | Speed Detection Signal | 6 Pulses/Cycle |
| Reduction Ratio | 1:5 | |
| Magnet Poles (2P) | 20 |
4. Setup and Installation
Installing the Bafang rear hub motor requires basic bicycle maintenance knowledge and tools. If you are unsure, please consult a professional bicycle mechanic.
- Compatibility Check: Ensure your bicycle frame's rear dropout spacing (OLD) is 135mm to match the motor's installation width. Verify your wheel diameter (20/26/27.5/28 inches) is compatible.
- Wheel Preparation: If replacing an existing wheel, remove the old wheel and transfer the tire, tube, and disc brake rotor (if applicable) to the new motor wheel.
- Cassette Installation: Install your bicycle's cassette (7S-9S compatible) onto the motor's freewheel body.
- Motor Mounting: Carefully insert the motor into the rear dropouts of your bicycle frame. Ensure the axle nuts are securely tightened to the manufacturer's specifications.
- Disc Brake Rotor (if applicable): Mount your disc brake rotor onto the motor's disc brake interface.
- Cable Connection: Connect the 800mm motor cable to your e-bike controller. Ensure the waterproof connector is fully seated and the individual phase wires (yellow, green, blue) are correctly matched if using a non-standard controller.
- Final Checks: Before riding, ensure all connections are secure, the wheel spins freely, and the brake system functions correctly.
5. Operation
The Bafang hub motor operates as part of an electric bicycle system. Its function is controlled by an e-bike controller, battery, and display (not included with the motor). Ensure these components are properly installed and configured according to their respective manuals.
- Power On: Turn on your e-bike system via the display or battery switch.
- Assist Level Selection: Use your e-bike display to select the desired pedal assist level. Higher levels provide more motor assistance.
- Pedal Assist: The motor will engage when you pedal, providing assistance based on the selected level.
- Throttle (if equipped): If your system includes a throttle, you can use it to engage the motor without pedaling.
- Power Off: Always turn off your e-bike system when not in use to conserve battery life and prevent accidental engagement.
6. Maintenance
Regular maintenance ensures the longevity and optimal performance of your Bafang hub motor.
- Cleaning: Keep the motor casing clean from dirt and debris. Use a damp cloth; avoid high-pressure washing directly on the motor or electrical connections.
- Cable Inspection: Periodically check the motor cable for any signs of wear, cuts, or damage. Ensure all connectors are clean and securely seated.
- Axle Nuts: Verify that the axle nuts are tight and secure before each ride.
- Spokes: Check spoke tension regularly, especially after the first few rides, to ensure the wheel remains true.
- Avoid Submersion: While the motor has an IP X5 rating (protected against low-pressure water jets), avoid submerging it in water.
7. Troubleshooting
If you encounter issues with your motor, consider the following common troubleshooting steps:
- Motor Not Engaging:
- Check if the battery is charged and properly connected.
- Ensure all electrical connections, especially the motor cable, are secure.
- Verify the e-bike system is powered on and an assist level is selected.
- Inspect for any error codes on your e-bike display.
- Loss of Power/Intermittent Power:
- Check battery charge level.
- Inspect motor cable and other electrical connections for loose contacts or damage.
- Ensure the motor is not overheating (allow it to cool down if ridden intensely).
- Unusual Noises:
- Check for loose spokes or objects caught in the wheel.
- Ensure the disc brake rotor is not rubbing.
- If the noise persists and seems to come from within the motor, discontinue use and consult a professional.
8. User Tips
- RPM Information: The motor has a nominal RPM (nT) of 255, which indicates its rotational speed under load.
- Regular Inspections: Perform quick visual checks of your motor and connections before each ride to catch potential issues early.
- Proper Storage: When not in use for extended periods, store your e-bike in a dry, temperate environment.
9. Warranty and Support
This Bafang hub motor comes with a one-year guarantee from the date of delivery.
- Within 15 days of delivery: The seller will cover the round-trip shipping postage for any product defects or damages that are the seller's fault.
- From 15 days to one year: The seller will cover the return postage for eligible warranty claims.
For warranty claims or technical support, please contact your point of purchase with your order details and a description of the issue.