Box Three Pro 108mm Brake Caliper

Box Three Pro 108mm Brake Caliper

The Box Three Pro brake caliper is a cold-forged aluminum U-brake designed for BMX racing with 108mm arm length and up to 35mm of brake pad adjustment range. Machined from 6061-T6 aluminum, this caliper delivers strong braking power while keeping weight at 207 grams. Includes Box Three Air Flow brake shoes with dual-compound pads and all necessary mounting hardware for complete installation.

Key Features

• Cold Forged 6061-T6 Aluminum – Cold forging process compresses the aluminum grain structure for increased strength compared to cast calipers; T6 heat treatment further enhances material properties for stiffness and durability under hard braking
• 108mm Arm Length – Pro-size arms provide increased leverage and modulation compared to shorter mini brake arms; delivers stronger stopping power with less hand force required at the lever
• Up to 35mm Brake Pad Adjustment – Wide adjustment range accommodates different rim widths and allows for precise pad positioning as pads wear; provides flexibility for various wheel and rim combinations
• Box Three Air Flow Brake Shoes with Dual-Compound Pads – Dual-compound pad design balances initial bite with consistent stopping power and pad longevity; air flow design helps dissipate heat during repeated hard braking
• Complete Hardware Included – All mounting bolts, springs, and hardware needed for installation come in the box; no need to source additional parts

Technical Specifications

• Material: 6061-T6 aluminum, cold forged
• Brake Type: U-brake (990-style)
• Arm Length: 108mm (Pro size)
• Brake Pad Adjustment: Up to 35mm
• Brake Shoes: Box Three Air Flow with dual-compound pads
• Weight: 207g (7.3 oz)
• Color Options: Black, Orange, Polished, Blue
• Includes: Brake caliper, pads, all mounting hardware

Compatibility and Ideal Use Cases

This brake caliper fits frames and forks with standard 990/U-brake mounts (welded or removable brake bosses). The 108mm Pro arm length is designed for 20″ and larger BMX race bikes where increased stopping power and modulation are needed. Best suited for competitive racers who need reliable, powerful braking for technical tracks with jumps, berms, and rhythm sections where precise speed control matters. The wide pad adjustment range makes this caliper compatible with various rim widths and allows riders to compensate for pad wear without replacing components. Not recommended for frames designed specifically for mini brake arms (shorter than 108mm), as the longer arms may contact the frame or tire.