Originally Posted by
glye
This is when you use the standard 28t physical chainring. When you use a 38t physical chainring, which you can if you order it with the 130 BCD chainring adapter, you get 38 / 54 / 68t equivalent. See
https://www.efneo.com/gearbox/technical-details/
You can go even bigger than the 38t physical, but I don't think there is any need. You can't use any size between 28 and 38. It must be either 28, or 38, or bigger.
Just received a reply from Efneo. 1st gear is direct drive with no efficiency loss. I believe my 36t cog should be enough for hills which I will test first of course. If not and I’ll need even lower then 38t will make sense. Then most likely the second gear will be used most of the time which will be less efficient. But if my 52t will do fine on hills do you think the 52t first gear will make sense as it’s a direct drive with no efficiency loss? Apparently Efneo will accept any
130BCD chainring. Then second gear can be used (74t equivalent) if 11t smallest cog will not be enough.
They also advised that it
can achieve chainline from 42mm to 46mm which I assume is within chain line distance of Birdy?
I will obviously start considering this if after extensive use the 11t smallest cog will not be enough.