S&M 19mm / 24mm Mid BB Kit

The S&M Mid BB Kit is a complete press-fit mid bottom bracket set available in both 19mm and 24mm spindle sizes, built around R-12 bearings and CNC machined anodised aluminium cone spacers. A full replacement or new build BB set covering the two most common BMX spindle diameters.

Key Features

• Available in 19mm and 24mm spindle sizes — Covers the two standard BMX crank spindle diameters; confirm your crank spindle size before ordering as these are not interchangeable
• R-12 bearings — High-quality R-12 rated bearings provide smooth, low-friction rotation and reliable load handling under the lateral and radial forces generated by pedaling and riding
• CNC machined anodised aluminium cone spacers — Precision machined spacers ensure accurate bearing positioning and consistent preload within the BB shell; anodising provides corrosion resistance and surface hardness
• Press-fit mid BB compatible — Designed specifically for press-fit mid BB shells, the most widely used BB standard in BMX; not compatible with Spanish or euro BB shells
• Spindle-specific center spacers — 19mm version uses a 2.005" (51mm) center spacer; 24mm version uses a 2.028" (51.5mm) center spacer, each sized to correctly position the bearings for their respective spindle diameter

Technical Specifications

• Brand: S&M Bikes
• BB shell compatibility: Press-fit mid
• Spindle options: 19mm / 24mm
• Bearings: R-12
• Spacers: CNC machined anodised aluminium cone
• 19mm center spacer: 2.005" (51mm)
• 24mm center spacer: 2.028" (51.5mm)

Compatibility and Ideal Use Cases

Compatible with press-fit mid BB shell frames only — not suitable for Spanish or euro BB shells. Select 19mm or 24mm to match your crank spindle diameter. Best suited to riders replacing a worn or damaged mid BB set or building up a new bike requiring a complete bottom bracket assembly.