When replacing a non drive side crank arm on an e-bike, compatibility and durability matter as much as form. This guide highlights five well-matched options designed for square or diamond hole crank interfaces, including models from BAFANG, PROWHEEL, and Alps2Ocean. Each entry notes length, interface, and material to help you choose a replacement that maintains balance, pedal feel, and pedaling efficiency without compromising motor compatibility. Use the quick reference table below to compare core specs at a glance.
| Product | Brand | Interface | ||
|---|---|---|---|---|
| BAFANG Crank Arm Only Right Side 170mm Diamond Hole | BAFANG Store | Diamond Hole | 170mm | Fits BBS02B/BBSHD mid-drive kits |
| PROWHEEL Ebike Crank Arm (Left) 170mm | PROWHEEL Store | Square taper | 170mm | 6 size options; for electric bikes only |
| BAFANG Crank Arm Only Left Side 170mm Diamond Hole | BAFANG Store | Diamond Hole | 170mm | Left side replacement for BBS02B/BBSHD |
| Universal Diamond/Square Hole Left Crank Arm | Various | Diamond or Square | 152–175mm, multiple options | Forged 6061 alloy, multiple hole types |
| Alps2Ocean Bike Crank Arm | Alps2Ocean Store | Diamond Hole | 89–175mm (10 sizes) | Sturdy forged alloy 6061 |
Note: When selecting a crank arm, ensure the spindle interface type and hole orientation match your existing left crank and your e-bike’s motor setup. Mismatches can affect crank alignment, chainline, and overall drive efficiency. The products listed here offer a range of hole types and lengths to suit common e-bike configurations, particularly those using mid-drive motors.
BAFANG Right Side Diamond Hole 170mm Crank
The BAFANG Crank Arm Only Right Side 170mm Diamond Hole is designed for BAFANG AC-08-2 style interfaces, compatible with BBS02B and BBSHD mid-drive kits. Crafted from aluminum alloy for durability, this crank features a Diamond interface hole and measures a 170mm hole spacing, with a total length of 210mm. This option is best paired with its left-side counterpart or the matching right arm in a full crank replacement scenario. It helps maintain proper pedal alignment and drive balance on compatible systems.
PROWHEEL Square Taper 170Mm Crank Arm (1 Pair)
PROWHEEL offers a 170mm left-side crank arm in a square taper interface as part of a 1-pair set. Made from forged alloy 6061, it emphasizes high strength and resistance to deformation. Available in six sizes (140–175mm), this crank arm is intended for use on electric bikes with a square taper orientation. Check that both crank arms share the same hole type to ensure proper pairing and pedaling symmetry. The 170mm size suits riders seeking a balanced stance on mid-drive configurations that require a longer lever for efficient power transfer.
BAFANG Left Side 170mm Diamond Hole Crank Arm
This left-side crank arm from BAFANG mirrors the right-arm design with Diamond Hole compatibility intended for BBS02B and BBSHD mid-drive kits. The 170mm hole spacing is compatible with most original crank setups, and the total length reaches 210mm. Aluminum alloy construction ensures a balance of light weight and durability, supporting stable pedaling and consistent chainline within mid-drive systems.
Universal Diamond Hole Left Crank Arm (152–175mm)
This universal left crank arm covers multiple sizes (152, 160, 165, 170, 175mm) and features a Diamond Hole interface. The forged alloy 6061 construction prioritizes rigidity and durability, with a 12cm Diamond Hole diameter noted for compatibility. It is compatible with left-side replacement on a variety of electric bikes and requires matching size and hole orientation with the right arm to maintain proper pedal alignment and spin efficiency.
Alps2Ocean Diamond Hole Crank Arm (10 Sizes)
The Alps2Ocean crank arms provide a broad size range (89–175mm across 10 options) with a Diamond Hole interface, making them a versatile choice for various e-bikes. Forged alloy 6061 construction ensures strength and stiffness, contributing to consistent power transfer and reduced flex under load. When selecting, confirm hole type compatibility and ensure the positive orientation of the crank to maintain the correct pedal engagement and chainline for your specific bike model.
Buying Guide: Key Purchase Considerations
When shopping for a non drive side crank arm, consider the following factors to ensure proper fit and performance:
- Spindle/Interface Compatibility: Confirm whether your bike uses Diamond Hole, Square Taper, or another interface and match both arms to this specification.
- Left vs Right Arm: Some replacements are side-specific. Verify whether you need a left-side, right-side, or a symmetric pair to maintain balance.
- Crank Length: Choose a length that aligns with your original crank or desired riding position. Common sizes include 152mm, 160mm, 165mm, 170mm, and 175mm.
- Material and Construction: Forged 6061 aluminum offers good strength-to-weight; ensure the finish and alloy type suit riding conditions and corrosion resistance needs.
- Hole Type and Diameter: Diamond Hole interfaces typically have specific alignment requirements; ensure the hole diameter (often around 12 cm in some products) matches your crank.
- Bike Compatibility: If your bike uses a mid-drive kit (e.g., Bafang BBS series), verify that the replacement matches the motor mount and crankset arrangement to avoid misalignment.
- Maintenance and Coverage: Look for arms with durable classifications and reliable seller support, especially if you plan to replace both arms or need replacements in the future.
Across these options, purchasers should weigh compatibility with the motor system, the intended riding style, and the desired balance of weight and stiffness. For riders who frequently ride on mixed terrain, opting for stiffer forged alloy arms can reduce flex and preserve pedaling efficiency. If your bike uses a diamond hole interface, you may prioritize arms explicitly advertised as “Diamond Hole” to avoid misfit issues.