Converting your bike to electric with a mid-drive motor opens up a new world of cycling possibilities. Mid-drive motors, such as the popular BBS02, seamlessly integrate with your bike’s existing drivetrain, amplifying your pedaling power with electric assistance. This system works by directly rotating the front chainring, which in turn drives the chain and rear gears, ultimately propelling your bike forward. From a rider’s perspective, it feels like having incredibly powerful legs that can pedal much faster and with significantly more force than your own.
The chainring size plays a crucial role in determining the performance characteristics of your electric bike conversion. Without delving into overly technical details, the size of the chainring dictates the amount of torque (rotational force) you get at a specific RPM (rotations per minute). Choosing the right chainring is essential for optimizing your e-bike’s performance based on your riding style and terrain.
Essentially, a smaller chainring will provide quicker acceleration from a standstill and reduce the strain on your motor, making it ideal for hill climbing and stop-and-go situations. However, it will limit your top speed. Conversely, a larger chainring will enable higher top speeds but will require the motor to work harder to achieve those speeds, potentially leading to increased heat generation and faster battery depletion.
To provide practical guidance, chainring sizes, measured by the number of teeth, can be broadly categorized into three types, each suited for different riding conditions:
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Small (30T) Chainrings: These are the optimal choice for riders who frequently encounter steep inclines. Mountain bikers and those living in hilly areas will benefit most from a smaller chainring as it maximizes torque for climbing and provides better motor efficiency in demanding situations.
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Medium (40-44T) Chainrings: A versatile option, medium-sized chainrings are well-suited for riders who experience a variety of terrains and prioritize a balance between climbing ability and top speed. This size is ideal for general commuting, recreational riding on mixed terrain, and riders who are not focused on high-speed downhill performance.
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Large (48-52T) Chainrings: Designed for flat terrain and riders seeking maximum speed, large chainrings excel on paved roads and level surfaces. If your rides primarily involve flat commutes or you desire to achieve higher speeds on your electric bike conversion, a larger chainring will be the most suitable choice.
Bafang mid-drive conversion kits typically include chainrings ranging from 44-52T, depending on kit availability. Beyond the standard options, the aftermarket offers upgrades like the Lekkie Bling Ring and other “narrow-wide” chainrings. A key advantage of these aftermarket chainrings, particularly narrow-wide designs, is enhanced chain retention. They significantly reduce the likelihood of your chain derailing, especially in bumpy terrain or during gear changes under motor power.
When fitting your chosen chainring to the motor, it’s helpful to refer to resources like this video guide around the 4:12 mark for visual tips. As a general rule, the default Bafang chainring should “dish” inwards, towards the motor. Always test the chainring fitment before fully tightening any bolts to ensure proper alignment and function.
One common issue encountered with certain conversion kits, such as some Luna Cycle kits, is that the included chainring bolts may be too long. As illustrated in the image above and this video, excessively long bolts can cause the chainring to rattle and even scrape against the motor housing. A simple solution is to replace the provided bolts with shorter ones. Origin8 Single-Ring Chainring Bolts are a readily available and effective replacement.
As shown in the final image, using correctly sized bolts ensures a secure and rattle-free chainring installation, completing a crucial step in your electric bike conversion process and optimizing your riding experience. Choosing the right chainring is a critical aspect of converting your bike to electric, directly impacting your bike’s performance and your enjoyment of the ride. By considering your typical riding terrain and desired speed, you can select the ideal chainring size to maximize your electric bike conversion.
