The best non-drive-side crank arm is one that matches your bike’s crank length and spindle interface. The Epessa arm is a straightforward 170 mm replacement with diamond- and square-hole options; the Alps2Ocean model offers more length choices for a diamond interface; and the PATHGNAR listing is a 170 mm square-taper pair intended for electric bicycles. Check your original crank before choosing: length, interface shape, and whether you need one arm or a pair all matter.
| Product | Best For | Key Fit Detail |
|---|---|---|
| Epessa Left Crank Arm | Common 170 mm replacements | Diamond or square interface options |
| Bike Crank Arms, Multiple Sizes | Square-hole size selection | 89–175 mm options |
| Alps2Ocean Diamond-Hole Arm | Diamond-interface replacements | 89–175 mm options |
| 170 mm Lightweight Left Arm | Single-arm replacement | Listing has conflicting hole-shape details |
| PATHGNAR 170 mm Pair | Electric-bike square-taper replacement | Pair; square taper |
Epessa 170 mm Left Crank Arm
This is a left-side replacement arm, making it a direct category match for a non-drive-side repair. It is made from aluminum alloy and is listed with either a diamond or square spindle interface. The listed hole spacing length is 170 mm, and the total arm length is 210 mm. It fits a 9/16-inch pedal, according to the product details.
Best for: Riders who need a 170 mm left crank arm and can select the interface that matches their existing spindle. Its separate interface options make it more adaptable than a listing with only one hole type.
Check before buying: Confirm the exact interface option, arm length, and pedal thread requirement. The product information does not identify a particular bike model, so do not assume compatibility without comparing your original part.
Square-Hole Crank Arm With Multiple Lengths
This square-hole crank arm is listed in lengths from 89 mm to 175 mm, including 170 mm. The feature details identify forged 6061 alloy and describe the arm as high-strength and resistant to deformation. The listing mentions use with e-bikes, mid-mounted motors, and torque applications, but the key fit requirement is still a matching square-hole interface and correct length.
Best for: Buyers who need a square-interface arm but require a length other than 170 mm, or want to match an existing nonstandard crank length. Multiple choices make it easier to compare sizes in one listing.
Check before buying: The product details say both crank sides should have the same hole type. Verify the selected length and confirm the interface on your bike; this listing is not suitable for a diamond-hole spindle.
Alps2Ocean Diamond-Hole Crank Arm
The Alps2Ocean arm is listed with a diamond-hole interface and ten length options from 89 mm to 175 mm, including 170 mm. Its features describe forged 6061 alloy and list applications such as electric, commuter, exercise, and fat bikes. The broad length range can help buyers seeking a specific crank measurement rather than assuming that every bike uses a standard 170 mm arm.
Best for: Riders whose original non-drive-side arm uses a diamond-shaped interface and who need a particular length. Choose this over a square-hole option only when the spindle shape matches.
Check before buying: The listing says both left and right arms should have the same hole type. It also specifies a crank-arm bolt tightening torque of 35–45 N/m and warns not to exceed 45 N·m; follow the product’s instructions and verify the correct unit and procedure for your setup.
170 mm Lightweight Left Crank Arm
This listing describes a 170 mm left crank arm made from aluminum alloy, with a stated weight of 7.1 ounces. It is presented as a replacement accessory for bicycles, including mountain and road bikes. However, its product name refers to a diamond hole while its feature text says the center opening is square and instructs buyers to confirm a square hole.
Best for: Buyers considering a 170 mm single-arm replacement who can resolve the hole-shape discrepancy with the seller or listing details before ordering.
Caution: Do not select this arm based on the title alone. The hole-shape information conflicts, so it is a less certain choice than a listing that clearly identifies the correct interface.
PATHGNAR 170 mm Square-Taper Pair
This product is listed as one pair of 170 mm crank arms made from forged 6061 alloy. The interface is square taper, and the listing says the arms can only be used on electric bicycles. Although a pair includes an arm for each side, it may be relevant when replacing a damaged non-drive-side arm if the buyer needs matching arms or a complete set.
Best for: E-bike owners who need 170 mm square-taper arms and want a pair rather than a single replacement.
Check before buying: Avoid this option if you need only one arm, your bike is not an electric bicycle, or your spindle interface is not square taper. The listed arm length must also match your current setup.
Buying Guide: How to Choose a Non-Drive-Side Crank Arm
Does the crank length have to match?
Match the replacement’s stated crank length to the original arm. The products here include fixed 170 mm options and models with lengths ranging from 89 mm to 175 mm. Measure or check the marking on your existing crank rather than estimating from appearance. A different length changes the distance from the spindle to the pedal and may affect your pedaling position.
How do I identify the spindle interface?
Inspect the opening where the crank attaches to the spindle. These listings describe square-hole or diamond-hole interfaces, which are not interchangeable. Compare the replacement opening with the original arm and confirm both crank sides use the same interface type. When product details conflict, as they do for the 170 mm lightweight listing, verify the shape before purchasing.
Should I buy one arm or a pair?
A single left arm is appropriate when only the non-drive-side part needs replacement and the existing opposite arm remains suitable. A pair may be preferable when replacing both sides or when matching arms are needed. Check the listing’s quantity carefully: the PATHGNAR product is described as a pair, while the other products are presented as individual crank arms.
What else should I check before ordering?
- Confirm the side required: non-drive-side generally means the left crank arm.
- Match crank length and spindle-interface shape to the original part.
- Check pedal fit where listed; the Epessa arm specifies a 9/16-inch pedal.
- Review intended-use limits, including the PATHGNAR listing’s e-bike-only statement.
- Follow the relevant installation instructions and use the appropriate crank bolt tightening procedure.
Frequently Asked Questions
Is the non-drive-side crank arm the left crank arm?
On a conventional bicycle, the non-drive side is the left side, opposite the chain and drivetrain. Confirm the orientation on your specific bike before ordering.
Can I replace only the non-drive-side crank arm?
Often, a single-arm replacement is an option if the other crank arm is serviceable and the replacement matches its length and spindle interface. Some listings sell a pair instead.
Are square-hole and diamond-hole crank arms interchangeable?
No. The crank-arm opening must match the spindle interface. Check the shape of your existing crank and spindle before choosing a replacement.
Is 170 mm a universal crank-arm length?
No. The products listed include several lengths, and the correct choice depends on the original crank and the rider’s setup. Match the existing length unless you have a specific reason to change it.
What should I do if a product listing gives conflicting hole details?
Do not rely on the product title alone. Confirm the interface shape with the seller or another reliable product detail before ordering, especially when the listing’s title and features disagree.