Check the listing for details. 128mm Alta Bicycle Conversion Kit Crank Set Chrome Bottom Bracket Kit Cruiser BB. Color: Chrome, Condition: New. Listed at 16.66 USD. Specifications: Shell Width:68mm: This conversion kit is designed to fit standard American bottom bracket shells with a width of 68mm, commonly found on cruiser, BMX, and vintage bicycles. Spindle Type:SQR JIS (Square Tapered Japanese Industrial Standard): The spindle features a square taper interface, which is the most common standard for three-piece cranksets. It ensures compatibility with a wide variety of crank arms designed for square-tapered bottom brackets. Cup Material:Steel: The bottom bracket cups are made of durable steel, providing excellent strength and longevity. Steel ensures that the bottom bracket will withstand the pressures of pedaling and off-road use. Threading Interface:24 TPI (Threads Per Inch): This is the threading standard for the cups, designed to fit American-style bottom bracket shells that have 24 TPI threading. Spindle Length:128mm: The spindle is 128mm in length, suitable for many three-piece cranksets. The length of the spindle determines the chainline, which is important for ensuring proper gear alignment on multi-speed bikes. Spindle Material:Chromoly (Chromium-Molybdenum Steel): The spindle is made from chromoly, a strong and lightweight alloy known for its durability. Chromoly spindles are more resistant to bending and wear than standard steel spindles. Color:Chrome: The chrome finish gives the bottom bracket conversion kit a polished, corrosion-resistant surface that adds aesthetic appeal while protecting against rust. Conversion Function:Converts 1-Piece to 3-Piece Cranksets: This conversion kit allows you to replace the old one-piece crank (common in American bottom brackets) with a more modern three-piece crank system. This upgrade provides better performance, efficiency, and a wider range of crankset options.Brand & Manufacturer:Brand: Alta, a recognized brand in the cycling industry known for offering durable and well-made bicycle components, particularly for cruiser and BMX bikes.Manufacturer: F&R Cycle Inc., a reputable manufacturer specializing in a wide range of bicycle parts and accessories, particularly for lowrider, cruiser, and custom bikes.Components Included: Spindle: Made of chromoly steel, with a 128mm length and square taper JIS interface. Bearing Cups: Press-fit steel cups that fit into the bottom bracket shell and house the bearings. These are threaded to accommodate American 24 TPI standard bottom brackets. Ball Bearings: Includes two sets of ball bearings that facilitate smooth crank rotation. Dust Covers/Seals: Protective dust seals or covers to prevent dirt and moisture from entering the bottom bracket area, increasing the lifespan of the bearings. Lockring and Retaining Hardware: Hardware to secure the bearing cups in place and prevent any unwanted movement during use.Functionality:1-Piece to 3-Piece Conversion: This kit allows you to convert older American-style bottom brackets that use one-piece cranks (common on vintage, cruiser, and BMX bikes) into modern three-piece cranks, which are lighter, more efficient, and offer a wider range of options.Improved Performance: By upgrading to a three-piece crank system, you get better pedaling efficiency, lighter components, and more precise crankset options, particularly important for multi-speed and performance bikes.Applications:Cruiser Bikes: Ideal for cruiser bikes that originally came with one-piece cranks but can be upgraded for better performance.BMX Bikes: Frequently used to convert older BMX bikes to accommodate three-piece cranksets.Vintage/Classic Bikes: Perfect for upgrading vintage bikes with outdated bottom bracket designs.Custom Builds: Ideal for custom bicycle builds where a modern crankset is desired on a frame that has an American-style bottom bracket shell.Advantages:Enhanced Performance: Switching to a three-piece crank provides better power transfer, smoother rotation, and lighter overall weight compared to a one-piece crank system.Durability: Chromoly spindles and steel cups provide long-lasting durability and are suitable for both recreational and performance cycling.Compatibility: Converts American-style bottom brackets (68mm) into a standard three-piece crank setup, which is widely supported by modern crank arms.