ethirteen Helix Core espec Cranks for ISIS Spindle - 155mm, 21.5mm Offset, Black

The ethirteen Helix Core espec Cranks offer high-end drivetrain integrity and a premium look at an exceptional value. Forged from tough 6066-T6 aluminum, these ultra-short 155mm crank arms are optimized to maximize ground clearance on modern low-BB e-MTBs, effectively eliminating pedal strikes. Featuring a 21.5mm offset for a compact, tailored Q-factor on standard ISIS spindle motors, they come complete with an alloy self-extractor system, steel pedal washers, and molded impact boots.

e*thirteen Helix Core e*spec Cranks for ISIS Spindle Motor Systems - 155mm, 21.5mm Offset, Black

The e*thirteen Helix Core e*spec Cranks deliver an exceptional e-bike drivetrain upgrade, combining high-end structural integrity and refined aesthetics at an extreme value. Engineered to withstand the relentless torque and punishing loads of modern e-MTB riding, these cranks ensure you never have to hold back on your next gravity run. By blending a value-conscious production layout with robust construction, e*thirteen provides privateers and daily trail riders with a reliable alternative to premium-priced models without sacrificing trail confidence.

This model is engineered for standard 24mm ISIS spindle motor interfaces, offering seamless compatibility with the market's leading e-bike platforms—specifically optimizing layouts for the Bosch SX, TQ HPR50, Brose S Mag, DJI Avinox, Yamaha, and Specialized 2.2/3.1 motor systems. Featuring a narrow 21.5mm offset, these cranks help maintain a highly efficient and compact stance width. Depending on your motor configuration, this offset achieves tight, tailored Q-factors: a precise 169.6mm on TQ platforms, 172.7mm on Bosch systems, and 186mm on Brose setups, striking an excellent balance between structural motor casing clearance and ergonomic pedaling alignment.

At an ultra-short 155mm length, these crank arms are an eMTB-preferred solution specifically tailored to solve the problem of pedal strikes on modern, low bottom-bracket frame geometries. Shorter crank lengths allow you to spin smoothly through tech-heavy, rock-strewn climbs with a fluid cadence, drastically reducing the risk of catching a pedal while maximizing your motor’s power output. For ease of maintenance, the arms feature an integrated alloy self-extracting crank bolt system that makes routine home workshop servicing and installation quick, simple, and efficient.

Weighing 497g, these stealthy black crank arms are forged from high-strength AL 6066-T6 aluminum to ensure maximum durability against heavy rock strikes and accidental casing. e*thirteen packs this economic upgrade with premium attention to detail, including durable steel pedal washers to protect the spindle threads from high-load deformation and custom-molded composite crank boots that act as a resilient shield against trail debris. Fully engineered for aggressive trail duty, the Helix Core e*spec cranks are backed by e*thirteen's dependable 5-year manufacturer warranty.

Key Features

• Forged AL 6066-T6 Aluminum Construction: Delivers high-end durability, structural stiffness, and dependable trail strength at an accessible price point


• Ultra-Short 155mm Length: Maximizes ground clearance on low-slung e-MTB geometries to prevent pedal strikes on technical singletrack


• Narrow 21.5mm Offset Profile: Yields an ergonomic, tighter stance with optimized Q-factors across compatible ISIS motor casings


• Standard 24mm ISIS Compatibility: Designed for flawless integration with Bosch SX, TQ HPR50, Brose S Mag, DJI Avinox, Yamaha, and Specialized systems


• Integrated Alloy Self-Extractor: Heavy-duty self-extracting bolt configuration makes installation and routine drivetrain maintenance efficient and tool-free


• High-End Hardware Inclusions: Comes equipped with durable steel pedal washers and high-impact molded protective crank boots for maximum longevity

Specifications

• Model: e*thirteen Helix Core e*spec Cranks


• Crank Arm Length: 155mm


• Spindle Interface Type: 24mm ISIS Spindle


• Crank Offset: 21.5mm


• Realized Q-Factors: TQ: 169.6mm | Bosch: 172.7mm | Brose: 186mm


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


• Material: Forged AL 6066-T6 Aluminum


• Pedal Thread Interface: Includes Steel Pedal Washers


• Extraction Mechanism: Integrated Alloy Self-Extractor System


• Protective Hardware: Molded Composite Crank Boots Included


• Weight: 497g


• Color: Black


• Warranty: 5 Years

A durable, value-optimized alloy e-bike crank arm upgrade combining a rock-clearing 155mm profile with a compact 21.5mm offset, built for trail riders who demand high-end e-MTB strength and reliability without the premium price tag.