e*thirteen Helix Race e*spec Direct Mount Chainring for Bosch CX/SX - 36T, 13mm Offset, Black

The e*thirteen Helix Race e*spec Direct Mount Chainring merges cutting-edge engineering with a refined technical aesthetic, delivering the ultimate drivetrain performance upgrade for modern electric mountain bikes (e-MTBs). Forged and precision CNC-machined from premium 7075-T6 aluminum, this one-piece direct mount chainring is purpose-built to handle the high-torque loads of aggressive e-bike riding. When paired with Helix Race Alloy e*spec crank arms, it creates a clean, fully integrated look that significantly enhances both the strength and style of your motor system assembly.

This Bosch-specific version features a 13mm offset, meticulously calculated to deliver precise, friction-free chainline optimization depending on your specific Bosch motor generation. For Bosch CX Gen 4 and lightweight Bosch SX motor systems, it yields an agile 53mm chainline. When mounted to the latest high-performance Bosch CX Gen 5 motors, it transitions perfectly to a wider 55mm chainline. This accurate offset prevents premature drivetrain wear, minimizes friction, and guarantees smooth shifting performance across the entire gear range of wide-ratio cassettes.

Drivetrain security is managed by e*thirteen's updated M4 narrow-wide tooth profile. This advanced long-wearing shape features enhanced tooth geometry that locks the chain securely in place over punishing, high-speed trail chatter, eliminating the absolute need for a heavy chain guide. Furthermore, the M4 profile offers comprehensive cross-compatibility with Shimano, SRAM, and TRP 11 and 12-speed drivetrains—including seamless operation on premium SRAM T-Type Transmission systems, allowing you to run your preferred shifter and cassette setup without compromise.

Weighing 127g, this 36T chainring is the largest size in the lineup, making it ideal for aggressive trail riders and high-speed e-bike applications where maximizing top-end speed on fire roads and fast singletrack descents is a priority. The one-piece design balances weight-saving performance with structural stiffness to prevent flexing under hard, out-of-the-saddle efforts. Finished in a durable, stealthy black anodized coating that protects the alloy against rock-strike abrasions and elements, it delivers maximum wear life and long-term reliability. The Helix Race e*spec chainring is compatible with all matching Bosch direct mount motor systems and is backed by e*thirteen's dependable 5-year manufacturer warranty.

Key Features

• Forged & CNC-Machined 7075-T6 Aluminum: One-piece construction delivers maximum structural stiffness, high wear life, and premium impact resistance


• M4 Narrow-Wide Profile: Advanced tooth geometry offers bulletproof chain retention across brutal trail chatter and eliminates chain drop


• Universal Drivetrain Compatibility: Engineered to run seamlessly with Shimano, SRAM, and TRP 11/12-speed systems, including SRAM T-Type Transmission


• Bosch Direct Mount Integration: Designed specifically for clean integration with Bosch CX Gen 4, Bosch CX Gen 5, and Bosch SX motor splines


• Optimized Drivetrain Chainline: 13mm offset achieves a 53mm chainline on CX Gen 4 / SX systems, and a 55mm chainline on CX Gen 5 platforms


• Maximum Speed Output: High-gear 36T profile provides a significant top-end push for high-velocity trail segments and open forest tracks

Specifications

• Model: e*thirteen Helix Race e*spec Direct Mount Chainring


• Tooth Count: 36T


• Motor Compatibility: Bosch CX Gen 4, Bosch CX Gen 5, Bosch SX


• Offset: 13mm


• Chainline Realization: CX Gen 4 / SX: 53mm | CX Gen 5: 55mm


• Drivetrain Compatibility: Shimano / SRAM / TRP 11-Speed & 12-Speed (Including SRAM T-Type)


• Tooth Profile: M4 Narrow-Wide


• Material: Forged and CNC-Machined AL-7075-T6 Aluminum


• Weight: 127g


• Color: Black


• Warranty: 5 Years

A premium, high-stiffness direct mount chainring built for aggressive e-MTB riders who demand zero chain drops, maximum high-speed efficiency, and long-term gear durability on high-torque Bosch motor systems.