Changing size of chainring on Bosch gen4 - do you need to update the software?

[Mteam]

If you change the size of the chainring on a Bosch gen 4 bike,do you need to update the config of the motor to tell it the new chain ring size, or is it possible to just change the ring without updating the software ?

It seems a pretty complex system,so wouldn't surprise me if the chain ring size is a factor in how much power or torque the motor puts out.

I was thinking of changing from a 34 tooth ring to 32.

 

[Planemo]

Good question.

I remember someone on this forum saying that the cassette ratios and chainring size (along with wheel size obvs) was indeed a parameter in the Bosch software which I was surprised at. So yes changing the ring could change things somewhat in relation to assistance in certain circumstances. That said I'm sure that going just 2 teeth down without touching anything else wont be catastrophic but it would be interesting to hear the exact details. Hopefully someone will pipe up

 

[emtbPhil]

Not sure about chainring but I know for a fact that crank arm length is something you have to update software for
So I'd guess chainring size too would need doing