Description:

The ethirteen Helix Race Alloy espec Cranks are a premium, high-strength alternative to carbon fiber, engineered specifically for high-torque ISIS spindle e-bike motors. Forged and precision CNC-sculpted from 6066-T6 aluminum, these ultra-short 155mm crank arms maximize ground clearance on modern low-BB geometries. Featuring a 26.5mm offset for a balanced Q-factor, integrated alloy self-extractors, and impact-absorbing crank boots, they deliver maximum durability and weight-efficient performance on Bosch, TQ, Brose, Yamaha, and specialized e-MTB platforms.

e*thirteen Helix Race Alloy e*spec Cranks for ISIS Spindle Motor Systems - 155mm, 26mm Offset, Black

Upgrade your electric mountain bike with the stiff, lightweight, and beautifully engineered e*thirteen Helix Race Alloy e*spec Cranks. Forged and precision CNC-sculpted from premium 6066-T6 aluminum, these high-performance crank arms offer an incredibly robust, impact-resistant alternative to carbon fiber without the weight penalty. Purpose-built to handle the demanding, high-torque output of aggressive e-MTB riding, they feature a low overall profile and pair seamlessly with Helix Race e*spec Direct Mount chainrings to deliver the ultimate combination of premium trail performance and clean, factory integration.

This model is engineered for standard ISIS spindle motor interfaces, providing extensive compatibility across the industry's leading e-bike platforms, including Bosch CX Gen 4/Gen 5, Bosch SX, TQ HPR50, Brose S Mag, DJI Avinox, Yamaha, and Specialized Turbo Levo/SL motor systems. Featuring a 26.5mm offset, these cranks achieve an optimized 182.9mm Q-factor. This precise geometry balances internal motor casing clearance with a natural, ergonomic stance width that optimizes pedaling efficiency and maximizes control when navigating technical trail features.

At an ultra-short 155mm length, these crank arms are explicitly designed to combat pedal strikes on modern, low bottom-bracket frame geometries. Shorter crank lengths allow riders to maintain a high, fluid pedaling cadence through rocky, root-strewn climbs, significantly improving technical climbing capability while enhancing descending stability. The assembly is built to last with premium 7075 alloy hardware, integrated alloy self-extractors for effortless tool-free extraction, and an e*thirteen Adaptive Preload System (APS) adjuster for simple, play-free bearing setup.

Weighing 413g, these stealthy black anodized crank arms are engineered to take a beating. The full CNC finish strips away unnecessary material to maximize the strength-to-weight ratio, while the included **custom-molded protective crank boots** act as a resilient shield against inevitable rock strikes and trail debris. Fully engineered for continuous, high-performance trail abuse, the Helix Race Alloy e*spec cranks are backed by e*thirteen's dependable 5-year manufacturer warranty.

Key Features

• Forged & CNC-Machined 6066-T6 Alloy: Sculpted structural design delivers maximum impact resistance and stiffness, serving as an elite alternative to carbon fiber


• Ultra-Short 155mm Length: Dramatically increases ground clearance on low-BB frame designs to eliminate pedal strikes on technical singletrack


• Standard ISIS Spindle Interface: Broadly compatible with Bosch CX Gen 4/5, Bosch SX, TQ HPR50, Brose S Mag, DJI Avinox, Yamaha, and Specialized systems


• Optimized 26.5mm Offset: Delivers a balanced 182.9mm Q-factor to ensure clear motor integration and a natural, ergonomic pedaling stance


• Premium Pro-Level Hardware: Outfitted with 7075 alloy hardware, an integrated self-extractor mechanism, and an APS bearing preload adjuster


• Huckproof Crank Boots Included: Includes custom-molded, high-impact composite protective boots to guard crank ends against rock-strike damage

Specifications

• Model: e*thirteen Helix Race Alloy e*spec Cranks


• Crank Arm Length: 155mm


• Spindle Interface Type: ISIS Spindle


• Crank Offset: 26.5mm


• Realized Q-Factor: 182.9mm


• Motor System Compatibility: Bosch (CX Gen4/5, SX), TQ (HPR50), Brose (S Mag), DJI (Avinox), Yamaha, Specialized (2.2/3.1)


• Material: Forged and CNC-Machined AL-6066-T6 Aluminum


• Hardware Material: 7075 Aluminum


• Extraction Mechanism: Integrated Alloy Self-Extractor


• Adjustment System: e*thirteen APS (Adaptive Preload System) Adjuster


• Weight: 413g


• Color: Black


• Warranty: 5 Years

A premium, high-stiffness alloy crank arm upgrade combining a rock-clearance-maximizing 155mm length with elite ISIS spindle motor compatibility, built for aggressive e-MTB riders who demand ultimate durability and weight-efficient power transfer.