A 155mm e-bike crank built around a narrow 21.5mm offset for Bosch SX, Brose S Mag and TQ HPR50 motor systems — forged and CNC-finished alloy at carbon-adjacent weight.

Highlights

  • 21.5mm offset, tuned for Bosch SX, Brose S Mag, TQ HPR50 (e*thirteen also lists it for Avinox and Specialized 2.2/3.1)
  • 24mm ISIS spindle with built-in self-extracting crank bolt
  • 155mm length for extra pedal-strike clearance on low-BB e-bike frames
  • Sterling Silver finish
  • Tested to e*thirteen's E-Enduro standard, EN17406 Class 5
  • No bottom bracket or chainring included

Built for e-bike torque

The narrow 21.5mm offset keeps a traditional MTB Q-factor feel while clearing the motor and chainstay on Bosch SX, Brose S Mag and TQ HPR50-equipped bikes.

Compatibility & fit

24mm ISIS spindle (mounts directly into the motor's drive-unit interface — there's no separate frame bottom bracket on this fitment), 155mm crank arm, 21.5mm offset. No bottom bracket or chainring included: pair it with a Helix Race e*spec direct-mount chainring (sold separately) and service it with the ISIS self-extractor bolt kit (CSS40-107).

e*thirteen covers this product for 10 years against manufacturing and material defects from the date of purchase; crash, impact or misuse damage qualifies for a discounted replacement under e*thirteen's Infinite Ride crash-replacement programme. This is in addition to your rights under the Australian Consumer Law, so keep your proof of purchase. For warranty support, return the product to Tune Cycles and we'll manage the claim with e*thirteen's Australian distributor.
  • 21.5mm offset for Bosch SX / Brose S Mag / TQ HPR50
  • 24mm ISIS spindle, self-extracting bolt
  • 155mm length
  • Sterling Silver
  • No BB or chainring included
Crank length155mm
Offset21.5mm
Spindle24mm ISIS
Motor fitBosch SX, Brose S Mag, TQ HPR50 (also Avinox, Specialized 2.2/3.1)
ColourSterling Silver
Weight413g
Chainring / BBNot included — sold separately
RatingEN17406 Class 5
Brand part numberZCS4HAA-108
SKU DTW-ETG-CS4HAA-108
Barcode # 4711280343768
Brand e*Thirteen
Shipping Weight 0.8000kg