About Mid-Drive

What is "Mid-drive"?

A mid-drive bicycle kit is one which positions the motor near the bottom bracket, and applies power through the front chain-ring. When installing a mid-drive kit, the bottom bracket, front chain-ring and cranks are replaced. The front derailleur can also be removed as it is no longer used. The rest of the bike remains unchanged.

Why choose a Mid-drive kit?

Load Distribution:

A mid-drive kit transmits all the torque of the motor through the bottom bracket. This is the strongest part of the bicycle and easily strong enough to cope with these forces.

Compatibility:

These kits will fit most bikes including road, commuter and mountain bikes. The only requirement is that it has a conventional threaded bottom bracket with a width between 68-73mm.

Gearing:

A mid-drive motor uses your existing gears. This means that it will work more efficiently (than a hub motor) when climbing hills or battling a nasty southerly.

Looks:

The motor controller for a Bafang mid drive kit is integrated into the motor housing, which avoids additional wires. A single multi-core control cable links the motor with the display, brakes and throttle. The battery is shaped to fit the drink bottle mounts. All of this makes for a comparably tidy installation.

Balance:

The weight of the motor is just forward of the bottom bracket so does not effect the balance or handling of the bike.

Performance

With a 300W Bafang e-bike kit you can easily cruise at speeds of 35km/hr or more - without even breaking a sweat. See complete specs below:

*Range recorded on flat roads using maximum pedal assist setting on a road bike applying light - moderate effort. Range value will be lower for a commuter or mountain bike. Range value will increase with increased rider effort or decreased assistance setting.

How much power do I need?

The chart below will give you an idea of the amount of power required to travel at a given speed. The chart has various different curves depending on what sort of riding position you are adopting (sitting upright (hands on hoods), hands on drops, or using Aero Bars). Note that the chart displayed below is for an 80kg, 6ft male riding a road bike. A smaller rider can expect higher speeds at the same power output. Conversely, if you are riding a mountain bike, or commuter bike then you can expect your speed to be less than that displayed.

For those of you interested, below are the parameters used to create the chart above:

• Drag coefficients: Hoods = 1.0, Drops = 0.88, Aero Bars = 0.8

• Frontal projected area: Hoods = 0.393 m^2, Drops = 0.352 m^2, Aero Bars = 0.291 m^2

• Rolling resistance coefficient: 0.011

What does it cost to run?

Below is a comparison of the daily running cost of various forms of transport for a 40 km return commute (costs as of 2019):

• Car (1.3L petrol) = $7.04

• Scooter (50cc petrol) = $2.64

• Bus (2 zones) = $7.70

• Bafang 300W E-bike = $0.12

You can see that the running cost of the E-bike is approximately 60 x cheaper than a petrol driven car. It's basically free!