I'm running 48/18 and sometimes it's too low (nice in a head-wind).

I'm thinking about putting a 16 or 17 tooth cog on the other side of the hub.

Any thoughts on which I should go with? Will going down to 16 be too much? I live in Boston.

Thanks.

17 imho

It's all related to your strength and preference but my strategy would be to start with 17 and if it's still not enough, go to 16.