Re: dax f80 with 36t or 41t sprocket?
For trail riding, definitely the 41- you'll have more power uphill-
You didn't say how much you weigh, but if it's more than about 125, you'll probably do better with the 41-
on the road I'd say 36- That's what I use- i'm almost 200 and the bike only bogs down on very long and steep climbs- and I'm in a very hilly region, for the midwest at least
If I had to go far here, I'd go with about a 40, but I'm probably going to be riding mostly on flat ground soon.