{"product_id":"lifetime-warranty-crank-left-arm-with-diamond-hole-170mm-aluminium-alloy-bicycle-crank-arm-left-replacement-for-mountain-bike-road-bike-black","title":"[Lifetime Warranty] Crank Left Arm with Diamond Hole, 170mm Aluminium Alloy Bicycle Crank Arm Left Replacement for Mountain Bike Road Bike (Black)","description":"\u003ch2\u003e170mm Aluminum Alloy Left Crank Arm (Diamond Hole)\u003c\/h2\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrecision Diamond Hole Interface:\u003c\/strong\u003e Features a square taper interface oriented at a 45-degree \"Diamond\" angle relative to the crank arm, ensuring compatibility with specific square-taper bottom brackets.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-Strength Aluminum Alloy:\u003c\/strong\u003e Forged from premium 6061 aluminum alloy to provide high fatigue resistance and durability while remaining lightweight for improved pedaling efficiency.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStandard 170mm Length:\u003c\/strong\u003e The most common crank arm length, providing an optimal balance between leverage for climbing and ground clearance to prevent pedal strikes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUniversal Pedal Threading:\u003c\/strong\u003e Features standard 9\/16-inch threading, making it compatible with almost all mountain, road, and indoor exercise bike pedals.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCorrosion-Resistant Finish:\u003c\/strong\u003e Treated with a deep black anodized coating that protects the metal from oxidation, road salt, and moisture.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eReplaces \/ Cross-Reference Part Numbers\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e170mm Left Crank Arm (Diamond Pattern)\u003c\/li\u003e\n\u003cli\u003eStandard Square Taper Replacement Arm\u003c\/li\u003e\n\u003cli\u003eDiamond-Hole MTB\/Road Crank Arm\u003c\/li\u003e\n\u003cli\u003e(Note: Not compatible with \"Square\" hole orientations where the flats are parallel to the arm).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCompatibility \u0026amp; Fitment\u003c\/h3\u003e\n\u003cp\u003eThis crank arm is a specific replacement part. Before purchasing, you must verify the hole orientation of your original arm:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHole Orientation:\u003c\/strong\u003e This is a \u003cstrong\u003eDiamond Hole\u003c\/strong\u003e. If your current crank arm hole looks like a square (sides parallel to the arm), this will not fit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBottom Bracket:\u003c\/strong\u003e Designed for standard Square Taper (JIS) bottom bracket spindles.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBicycle Types:\u003c\/strong\u003e Mountain Bikes (MTB), Road Bikes, Fixed Gear (Fixies), and many Indoor Spin\/Exercise bikes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePosition:\u003c\/strong\u003e This is the \u003cstrong\u003eLeft Side (Non-Drive Side)\u003c\/strong\u003e arm only.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhen to Replace\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eRounded-Out Hole:\u003c\/strong\u003e If the crank arm was ridden while loose, the square hole becomes \"rounded,\" causing the arm to wobble or fall off the spindle.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eStripped Pedal Threads:\u003c\/strong\u003e The internal threads where the pedal attaches are cross-threaded or flattened, making it impossible to secure the pedal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eVisible Cracks:\u003c\/strong\u003e Stress fractures appearing near the spindle interface or the pedal eyelet, often caused by high-impact jumps or metal fatigue.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBent Arm:\u003c\/strong\u003e The arm is visibly warped from a crash or a heavy pedal strike, causing an uneven pedaling motion that can lead to knee pain.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eInstallation Tips\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eVerify Orientation Twice:\u003c\/strong\u003e Hold your old crank arm and the new one side-by-side. Ensure the square holes are oriented in the same \"Diamond\" direction. If they are different, your pedals will be 45 degrees out of sync.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClean the Spindle:\u003c\/strong\u003e Before installing, use a rag to wipe away all old grease and metal shavings from the bottom bracket spindle.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGrease the Threads:\u003c\/strong\u003e Apply a small amount of bicycle grease to the \u003cstrong\u003epedal threads\u003c\/strong\u003e, but keep the \u003cstrong\u003esquare taper spindle\u003c\/strong\u003e clean and dry (or apply a very thin film of oil) to ensure a solid friction fit.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTighten to Spec:\u003c\/strong\u003e Use an 8mm hex wrench or 14mm socket to tighten the crank bolt firmly (typically 35–45 Nm). A loose bolt is the #1 cause of rounded-out crank holes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRetighten After First Ride:\u003c\/strong\u003e Check the tightness of the crank bolt after your first 10–20 miles. The aluminum \"sets\" onto the steel spindle and often requires a final snugging.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"BlueStarsParts","offers":[{"title":"Default Title","offer_id":46495303827645,"sku":"AZ00220972","price":17.32,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/2576\/7548\/files\/AZ00220972_1.jpg?v=1773213045","url":"https:\/\/bluestarsparts.com\/products\/lifetime-warranty-crank-left-arm-with-diamond-hole-170mm-aluminium-alloy-bicycle-crank-arm-left-replacement-for-mountain-bike-road-bike-black","provider":"BlueStars Parts","version":"1.0","type":"link"}