Narrow-fit carbon eCrank arms for road, gravel and urban eBikes with a Brose Mag family, Fazua Ride 50 or TQ HPR50/HPR60 motor on a steel ISIS-spline spindle. Use them to change crank length or move to carbon arms, with Praxis's self-extracting M24 alloy main bolt already fitted.

Highlights

• Type 4 narrow road/gravel arm shape. Praxis says it will not fit an eMTB
• For Brose Mag family, Fazua Ride 50 and TQ HPR50/HPR60 ISIS-spline motors, plus Giant E+ System BBSS
• C.R.A.F.T. carbon left and right arms
• 385g for a 172.5mm set (Praxis figure)
• Replaceable M24 alloy main bolt with built-in self-extractor, 8mm hex, 50Nm

Fitting

Fitting eCrank arms is a separate workshop service and isn't included in the price. The Tune workshop can fit them and confirm your motor and spindle first. Praxis specifies a torque wrench with an 8mm hex for the M24 main bolt (50Nm). The bolt comes pre-installed and doubles as a self-extractor, so the arm comes off with the same 8mm hex. Praxis's manual says to re-check the torque after about the first 100km.

Which Praxis eCrank type fits?

Praxis sorts its eCranks by the motor's spindle and the arm shape. Its fit guide (April 2026) matches them like this:

• Type 1: older Bosch Gen4 CX (BDU37) and SX (BDU31), Yamaha PW-X, Giant SyncDrive Pro
• Type 2 (MTB): Bosch Gen5 CX (BDU38) and PX (BDU34), Avinox (DJI) M1/M2/M2S, Qore (Brose) Drive3, Specialized Levo 4
• Type 3 (MTB): Brose S-Mag, TQ HPR50/HPR60, Fazua Ride 50, Bafang M800, SRAM Powertrain
• Type 4 (narrow road/gravel): Brose S-Mag, Fazua Ride 50, TQ HPR50/HPR60, Giant E+ BBSS
• Type 5 (road/gravel): TQ HPR40
• Type 6 (ETOR alloy spindle): Fazua Ride 60 and Maxon AIR-S (MTB and road/gravel), Mahle M40 (MTB)
• Specialized Turbo-ISIS: Gen 1–3 Levo, Kenevo, Vado, Como (asymmetric arms)
• M30/SL1.1: Specialized SL 1.1 motor

Options

Every option is the same carbon Type 4 arm set; only the crank length changes. A forged alloy Type 4 set in 170mm is listed separately.

Compatibility & fit

Type 4 arms fit these motors on their steel ISIS-spline spindle, with the Q-factor Praxis quotes for each:

• Road, gravel and urban eBikes only. Praxis says these narrow arms will not fit an eMTB. For the same motors on a mountain bike, choose Type 3.
• Not for Specialized Levo, Kenevo, Vado or Como. Praxis says not to order this crank for them.
• Not for Fazua Ride 60 (ETOR spindle, Type 6), TQ HPR40 (Type 5), or Bosch, Avinox and Brose Drive3 (Types 1 and 2).
• Left and right arms only. No chainring is included.
• Unsure what your bike has? Check your motor's crank interface with our workshop before ordering.