hello you would choose the motor spindle size to match your BB length so 120mm. should b ok. id recommend looking at a cyc photon although depending on your needs, ie how much weight youre pushing a BBSHD has 160 Nm of max torque vs 110 Nm on a photon, so 40-45% more power on a bbshd for heavy duty use if you dont mind the extra weight
hello you would choose the motor spindle size to match your BB length so 120mm. should b ok. id recommend looking at a cyc photon although depending on your needs, ie how much weight youre pushing a BBSHD has 160 Nm of max torque vs 110 Nm on a photon, so 40-45% more power on a bbshd for heavy duty use if you dont mind the extra weight