Choosing a reliable left crank arm is essential for bike performance and safety. The left crank connects the pedal and chainring to the bottom bracket and must match your bike’s spindle interface and length. Diamond and square hole orientations are common, and 170mm is a versatile standard for many riders. The following five options are well-regarded left crank arms available on Amazon, covering a range of materials and sizes to fit mountain, road, hybrid, and e-bike setups. Each product highlights compatibility, durability, and ease of installation to help you choose confidently.
| Product | Brand | Length | Hole Type | Compatibility |
|---|---|---|---|---|
| Rhinenet Left 170mm Crank Arm | Rhinenet | 170mm | Diamond Hole | Left crank arm for various bikes |
| Alps2Ocean Universal Left Crank Arm | Alps2Ocean | 152–175mm (several options) | Diamond Hole | Left crank for city, MTB, ebike, road |
| WEEROCK Left 170mm Crank Arm | WEEROCK | 170mm | Diamond Hole | Left crank replacement for multiple bikes |
| THALOUS Universal 170mm Crank Arm | THALOUS | 170mm | Diamond Hole | Left crank for MTB, road, ebike |
| BLLREMIPSUR 2 Pcs Left Crank Arm | BLLREMIPSUR | 170mm | Diamond Hole (front; diamond) / Square compatibility noted | Left crank replacement for multiple models |
Rhinenet 170mm Left Crank Arm – Diamond Hole
Rhinenet’s left crank arm is designed for dependable left-side installation with a diamond-hole spindle. The 170mm length aligns with many mountain, road, and hybrid bikes. The product emphasizes durability and reliable performance for daily riding and maintenance tasks.
- High-quality materials with strong durability; built for reliable use.
- Specifically described as the LEFT crank arm; easy to install and operate.
- Length: 170mm; optimized to fit without interference with chainring bolts.
Alps2Ocean Universal 152–175mm Left Crank Arm
Alps2Ocean offers a forged alloy 6061 left crank arm available in multiple sizes from 152mm to 175mm. This design supports a diamond-hole interface and emphasizes stiffness and resistance to deformation. It suits city bikes, folding bikes, MTBs, and ebikes, with easy installation and compatible dimensions for a balanced ride.
- Material: Forged Alloy 6061 for strength and durability.
- Available in 152–175mm in 5 size options; ensure length matches crank and frame.
- Diamond Hole interface; check orientation to match your left crank.
WEEROCK Left 170mm Diamond Hole Crank Arm
WEEROCK’s left crank arm is a steel 170mm replacement designed for durability and straightforward installation. It specifies a diamond-hole interface, making it compatible with many bicycles using the same hole orientation. A solid choice for riders seeking a robust, long-lasting option.
- Material: Steel for high strength and impact resistance.
- Length: 170mm; compatible with diamond-hole spindles.
- Simple installation suitable for a range of bike models.
THALOUS Universal 170mm Diamond Hole Crank Arm
THALOUS presents a universal left crank arm at 170mm length with a diamond-hole interface. Made from forged aluminum alloy 6061-T6, it emphasizes high strength, light weight, and durability. The product notes ensure correct hole orientation and compatibility with 9/16″ pedals for a broad range of bikes, including MTB and ebikes.
- Material: Forged aluminum alloy 6061-T6 for lightness and strength.
- Diameter and hole type: Diamond Hole; confirm crank orientation before purchase.
- Length: 170mm; compatible with 9/16″ pedals.
Buying Guide
Choosing the right left crank arm involves balancing fit, durability, and compatibility. This buying guide covers key considerations and practical comparisons to help you decide which option matches your bike and riding style.
- Crank arm length: Common options are 152mm to 175mm. Shorter arms reduce knee strain for some riders, while longer arms may improve leverage for others. Confirm your inseam, crankset, and pedal position before buying.
- Hole type and orientation: Diamond hole and square hole are the two prevalent interfaces. Ensure your bottom bracket spindle and the left crank match; misalignment can cause installation problems or poor performance.
- Material and durability: Aluminum alloy (6061-T6) is common for light weight and stiffness, while steel offers ultimate strength and impact resistance. Consider riding style and maintenance expectations when selecting.
- Compatibility scope: Some arms are universal across many bike types (city, road, MTB, ebike), while others are model-specific. Check the product description for compatibility notes and any required adapters.
- Installation considerations: Look for arms that note easy installation with standard crank bolts and compatible pedal threads (e.g., 9/16″). Some sets include hardware or require separate bolts; plan accordingly.
- Left vs right crank alignment: Always verify you are purchasing a left crank arm if that is your aim. Not all left arms are interchangeable with every frame or crankset.
- Maintenance and wear: Periodic inspection of crank arms for cracks or deformation is important, particularly with steel arms and older bikes. Replace any arm showing signs of fatigue.
- Brand reliability and warranty: Reputable brands with clear specifications and warranty support can save time and ensure proper fit and performance.
In summary, the best choice depends on your bike’s hole orientation, length requirements, and the level of durability you need. The five products highlighted here offer solid left-crank options across different materials and lengths, with diamond-hole compatibility that covers a wide range of models. Always confirm compatibility with your specific bottom bracket, chainring clearance, and pedal threading before making a purchase.