Box Two Chain Tensioners

Product Overview

Box Two chain tensioners are adjustable dropout-mounted devices designed to maintain proper chain tension on BMX bikes with horizontal or semi-horizontal dropouts. The dual mounting holes provide fine adjustment range to dial in optimal chain slack, protecting frame dropouts from stress while keeping your rear wheel securely positioned. Essential for bikes without internal gearing or derailleur systems that require manual chain tension management.

Key Features

• Dual mounting holes – Two adjustment positions on each tensioner provide a wide range of fine-tuning capability to accommodate different chain lengths and frame geometries
• Horizontal dropout compatibility – Designed for frames with horizontal or semi-horizontal rear dropouts common to BMX, fixie, and single-speed bikes
• Dropout protection – Proper chain tension reduces stress and movement at the dropout, extending frame life and preventing potential cracking or deformation
• Wheel retention – Maintains rear wheel axle position in the dropout, preventing accidental wheel slip during hard braking or acceleration
• Adjustable tensioning – Allows you to dial in the precise amount of chain slack needed for your specific setup without over-tensioning
• Universal compatibility – Works with standard 10mm axles and most horizontal dropout frame designs

Technical Specifications

• Axle compatibility: 10mm
• Mounting: Dropout-mounted with dual adjustment holes
• Type: Chain tension adjuster
• Material: Steel (standard construction)
• Quantity: Sold as pair (left and right)

Compatibility & Ideal Use Cases

Box Two chain tensioners fit any BMX or single-speed bike with 10mm rear axles and horizontal or semi-horizontal dropouts. They're essential for fixed-gear BMX setups, track bikes, and any frame without internal gearing where manual chain tension adjustment is required. Proper tensioning prevents chain slippage during hard acceleration, protects frame dropouts from stress concentrations, and ensures predictable rear wheel positioning. Not necessary for frames with vertical dropouts or internal chain tensioning systems. Compatible with all standard 10mm BMX rear hubs and axles.