Black Ops One-Piece Crank Sealed Bottom Bracket – 24 TPI – 51mm – Chrome

This Black Ops sealed bottom bracket set is designed for bicycles running a one-piece crank (OPC) system. It features a sealed bearing mechanism and chrome-plated steel cups.

This is for traditional BMX, cruiser, and older steel frame bikes that use American (Ashtabula) style bottom bracket shells. Confirm shell size and crank type before ordering.

Key Functional Details

• Designed for one-piece crank (OPC / Ashtabula) systems
• Thread pitch: 24 TPI
• Sealed bearing mechanism
• Press-fit cup design
• Cup outer diameter: 51mm
• Cup material: Chrome-plated steel (CP)
• Weight: Approx. 310–315g
• Spindle Type: OPC (One-Piece Crank)
• Platform Type: BMX / Cruiser / Vintage

Compatibility & Technical Notes

• Fits frames with American (Ashtabula) bottom bracket shell
• Shell inner diameter: 51mm required
• Designed for one-piece crank arms only
• Does NOT fit 3-piece crank systems
• Does NOT fit Mid, Spanish, Euro, or PressFit 30 systems
• Requires 24 TPI compatible one-piece crank spindle
• Press-fit cup installation required
• Platform Type: BMX / Cruiser / Youth

Service / Ownership Context

This bottom bracket presses into the frame’s 51mm American bottom bracket shell. Installation requires proper bottom bracket cup press tools. Sealed mechanism reduces maintenance compared to loose-ball OPC setups.

Fit & Use Signals

• Good Fit: Your bike uses a one-piece crank.
• Good Fit: Your bottom bracket shell measures 51mm ID.
• Good Fit: You are replacing an older loose-ball American BB.
• Not A Fit: Your bike uses a 3-piece crank.
• Not A Fit: Your frame uses Mid, Spanish, or Euro bottom bracket.
• Not A Fit: You are unsure what bottom bracket standard your frame uses.