Originally Posted by
glye
For zero drag with lights off there is the Velogical rim dynamo which I have on another bike: [URL removed]
It runs on the rim, not the tyre as the old style bottle dynamos do, so there is no tyre wear. It is also extremely small and light weight. It is an easy retrofit since there is no need to rebuild the wheel. The only downsides are the cost (still less than SON) and some running noise (where hub dynamos are completely silent).
Ah, this almost feels like a chat by now with these fast responses :-)
I like this alternative even better since there is no drag when not in use.
I could probably live with a little noise while in use. That does not disturb me too much on my ebikes either.
And regarding the cost: It's still cheaper if you add (re-)building a Birdy wheel, no?