E-BIKE MOTOR Front, Back, or Mid?

Where best your e-bike motor – front wheel, rear wheel, or in between?

Until now the majority of production electric bikes have had a hub motor in the rear wheel. The more powerful (ie “offroad”) will stay with rear wheel drive, either hub motor or chain motor, because they need all the traction they can get, and there is more weight on the rear wheel.

For bike conversions you can choose either front wheel or rear wheel drive. Several factors influence your choice.

If you ride tracks a rear wheel drive is better because even the lower power 250 watt bikes with front wheel drive lose traction on sandy or loose tracks.

If you have “cassette” gears and not a screw on gearset and you’d prefer to keep those then you (may) need a front wheel motor, because rear wheel motors mostly have provision for screw on gears. There are only few motors for cassette gears, and they are more expensive.

If you are likely to be swapping your powered wheel and original wheel then it’s easier to do that with the front wheel.

Mid mounted motors for conversions are possible and there are some kits for that. These have used a motor attached by a bracket to the bike and driving the chain with a small sprocket. That arrangement is more difficult to install.  Motors that integrate the chainwheel and cranks that fit into the bottom bracket (where pedal axle is) are now available and they are easier to install.

The difference between front wheel and rear wheel drive for a bicycle is much the same as it is for a car.  It’s a personal choice.

There’s a trend away from rear motor towards front wheel hub motors or mid mount chain driving motors in production bikes. 

The hub motors for a front wheel are very similar to the ones for a rear wheel. They need to fit into a 100mm space between the forks instead of 135mm for a rear fork. Usually a motor is designed to fit either front or rear so the only noticeable difference is that the front motor is missing the lug which gears attach to and has a shorter axle. There is very little cost or weight difference.

More brands of electric bikes are now being produced with a motor between the pedals or adjacent to the pedals. This is achieved 3 ways.

  • Integrated pedal, chainwheel and motor in specially designed frame. The motors are made by Panasonic or Bosch. They are welded to the bike frame and they completely replace the bottom bracket. The systems are expensive, and so are the bikes that incorporate them, but are becoming common in Europe with many brands having a mid drive motor, especially Bosch. The Europeans are much more accustomed to paying a high price for a bicycle and they do expect quality parts.
  • A separate motor attaching to chainwheel or pedal axle. Some bikes from China have these systems. They are much cheaper – similar in price to the hub motor bikes from China.
  • A motor incorporated into the bottom bracket inside right pedal crank.These are made by Bafang in China (a motor of good repute)These can be fitted into bottom bracket of (most?) bikes replacing chainwheel and pedals and so can convert (most?) ordinary bikes to e-bikes. I see one big e-bike brand in US will be selling bikes with these motors. The cost for this system is a little more than the systems with separate motor and much less than the Bosch or Panasonic systems. I expect they will be more reliable and simpler to operate than the cheaper systems with separate motors

You can read about the pros and cons for these mid drive systems elsewhere.

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