Did you change anything after fitting shorter cranks?

[maxcycles]

Considering going down to 155’s from the stock 165’s on my Reign E+. Having to reprogram the drive unit for shorter cranks was something that I hadn’t considered needing to do. My assumption is that most folks just throw the shorter cranks on and ride without any software updates. That said, I understand Bosch has a shorter crank update. Does anyone know if Yamaha/Giant has the same type of software update for shorter cranks, or really if it’s even necessary to do so?

 

[Mikerb]

The reason Bosch introduced the short crank setting was because it was thought many average riders would not be able to generate enough torque to access the full motor assist power. Personally I think there is a bigger differential in terms of torque between 165 and 175 than there is between 165 and 155 but those with more physics/dynamics knowledge may know better!
It is also the case that as standard the bosch cx needs a higher cadence on average to access the max nm than say the Brose motor. I have no experience of the Yamaha motor but if the max nm is delivered at lower cadences you may notice little difference.
Note the short crank setting on the Bosch cx only applies to the EMTB mode.....ie a mode that enables full nm from the motor depending on rider input.

 

[maxcycles]

The reason Bosch introduced the short crank setting was because it was thought many average riders would not be able to generate enough torque to access the full motor assist power. Personally I think there is a bigger differential in terms of torque between 165 and 175 than there is between 165 and 155 but those with more physics/dynamics knowledge may know better!
It is also the case that as standard the bosch cx needs a higher cadence on average to access the max nm than say the Brose motor. I have no experience of the Yamaha motor but if the max nm is delivered at lower cadences you may notice little difference.
Note the short crank setting on the Bosch cx only applies to the EMTB mode.....ie a mode that enables full nm from the motor depending on rider input.

Thanks for the insight, that’s very helpful. The sync drive Yamaha motor definitely operates well at a low RPM in my experience, especially coming from a Shimano equipped bike previously that seemed to require a high cadence to get the most out of the motor. I think I’ll go for it and try the shorter cranks, maybe along with a smaller chainring if needed which would probably make the change even less noticeable.

 

[Husky430]

The reason Bosch introduced the short crank setting was because it was thought many average riders would not be able to generate enough torque to access the full motor assist power. Personally I think there is a bigger differential in terms of torque between 165 and 175 than there is between 165 and 155 but those with more physics/dynamics knowledge may know better!
It is also the case that as standard the bosch cx needs a higher cadence on average to access the max nm than say the Brose motor. I have no experience of the Yamaha motor but if the max nm is delivered at lower cadences you may notice little difference.
Note the short crank setting on the Bosch cx only applies to the EMTB mode.....ie a mode that enables full nm from the motor depending on rider input.

I have a Bosch powered Focus and went from the standard 165mm cranks to 155mm and didn't notice any difference with the motor or have any difficulties with generating enough torque. Didn't even know that there is some special Bosch update for the electronics for that.
The cranks seem to spin up to a higher cadence a bit quicker, though that might just be in my head.
The main difference is that pedal strikes are virtually eliminated, although I didn't suffer many, it's much better clearance and by the way I generally ride in EMTB mode. Hope this helps.