Hub Motor

Summary

A hub motor is an electric drive system integrated directly into the front or rear wheel hub of an e-bike. It delivers silent, independent propulsion and is commonly used for commuter, city, and budget-oriented e-bikes due to its simplicity, affordability, and ease of installation.

Key Facts

  • Introduced: Commercial use since the early 2000s; concept dates to early 20th century
  • Category: E-Bike Systems
  • Also known as: Wheel hub motor, direct-drive motor, geared hub motor
  • Used by / Found on: Rad Power Bikes, Aventon, VanMoof, Ride1Up, Juiced, and many others
  • Common motor output: 250–750 watts nominal; torque varies by design
  • Typical applications: Urban, commuter, folding, light-duty cargo, recreational
  • Official website: Not applicable

Overview

Hub motors are among the most widespread and accessible e-bike motor types. As the name implies, the motor itself is built into the hub of the wheel — usually the rear wheel, but sometimes the front. Unlike mid-drive motors, which apply power through the drivetrain, hub motors drive the wheel directly, creating a simple and contained propulsion system.

This design has proven especially popular in the affordable and commuter e-bike segments. With fewer moving parts and minimal frame integration requirements, hub motors offer an easy way to electrify a bicycle — whether in a factory-built model or through aftermarket conversion kits. Rear hub motors dominate the category due to better traction and handling, but front hub motors still appear in step-through or folding bikes.

Hub motors are also found in performance e-bikes with lightweight “stealth” designs. These systems typically use compact, geared hub motors for minimal drag and integrated batteries for a clean silhouette — appealing to riders who want electric assist without the look or complexity of a full mid-drive system.

Over the last decade, the technology behind hub motors has matured. Improved torque sensors, smarter controllers, and more efficient motors have helped elevate the ride feel, especially at the mid- to high-end level. However, the core appeal of hub motors remains unchanged: they’re simple, quiet, affordable, and easy to live with.

How It Works

Types of Hub Motors

There are two primary hub motor architectures:

  1. Geared Hub Motors
    • Use internal planetary gears to reduce motor RPM and increase torque
    • Freewheel clutch disengages motor when not in use (low drag)
    • More compact and efficient at low speeds
    • Slight mechanical noise from gear operation
    • Most common design for modern hub-drive e-bikes
  2. Direct-Drive (Gearless) Hub Motors
    • Large motor rotates entire hub shell
    • Silent operation with no moving internal gears
    • Higher weight and less torque at low speeds
    • Capable of regenerative braking
    • Common in older designs or high-power speed pedelecs

Operation

Hub motors work independently of the drivetrain. When activated, they apply rotational force directly to the wheel axle or hub shell — turning the wheel without relying on chain, cassette, or crank motion. This enables:

  • Throttle-only operation (on some models), independent of pedaling
  • Pedal-assist (PAS) mode, triggered by cadence or torque sensors
  • No interference with shifting, because power doesn’t pass through the chain

Most hub motors are brushless, using a series of permanent magnets and stator coils to generate torque. The controller regulates current based on the rider’s input and the selected assist level.

Sensors and Control

Hub motors typically use:

  • Cadence sensors (common in budget e-bikes): Detect crank rotation to enable motor assist
  • Torque sensors (mid-tier and up): Measure rider effort and deliver proportional assist
  • Speed sensors: Regulate motor output as bike approaches assist speed limits

These inputs allow the system to deliver appropriate assistance while staying within legal speed thresholds — typically 20 mph (Class 1/2) in the U.S. or 25 km/h in the EU. Some models support Class 3 speeds (28 mph) using higher wattage or throttle support.

Advantages & Limitations

Advantages

  • Simplicity: Fewer moving parts, no drivetrain integration
  • Low Cost: Ideal for entry-level e-bikes and conversion kits
  • Independent Drivetrain: No added chain or cassette wear
  • Quiet Ride: Especially true of direct-drive designs
  • Throttle Support: Common in hub systems, rare in mid-drives
  • Easy to Retrofit: Many DIY kits use hub motors for simplicity

Limitations

  • Less Efficient on Hills: Can’t leverage bike’s gearing like mid-drives
  • Poor Weight Distribution: Rear-heavy balance can affect handling
  • Lower Torque Output: Especially in small geared motors
  • Flat Tire Hassle: Rear flats require motor cable disconnection and extra steps
  • Limited for Aggressive Terrain: Not ideal for technical mountain biking

In general, hub motors thrive in urban, flat, or mild terrain where simplicity and silent propulsion are valued more than off-road torque or climbing performance.

Notable Implementations

  • Rad Power Bikes RadRunner / RadCity – 750W geared rear hub motors on Class 2 utility bikes
  • VanMoof S5 / A5 – Sleek front hub motor with torque sensor and automatic shifting
  • Aventon Level.2 – Commuter e-bike with integrated 500W rear hub drive and torque sensing
  • Ride1Up 700 Series – Affordable city e-bike with rear hub and high-capacity battery
  • Swytch Kit – Compact front hub conversion kit for turning any bike into an e-bike
  • Mahle X35 / X20 – Ultra-light rear hub motors found on “stealth” road and gravel e-bikes

Related Terms

See Also on BBB

References

  • ElectricBikeReview: Hub vs Mid Motor Guide
  • EbikeSchool.com: Hub Motor Tech Breakdown
  • Mahle Smartbike Systems Technical Overview
  • VanMoof Tech Specs
  • Rad Power Bikes Motor Documentation
  • Electrek: Hub Motor vs. Mid-Drive Explained
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