Joined: Feb 2013
Posts: 1,472
Likes: 11
From: Near St. Louis, Missouri
Bikes: Giant Defy Advanced, Breezer Doppler Team, Schwinn Twinn Tandem, Windsor Tourist, 1954 JC Higgens
If you go that small, you will need new tubes.
I'm your weight an ride on 700x25s. Properly inflated, you shouldn't have any pinch flats. I pump up to 100 psi.
However I wouldn't recommend anything less than 700x28s as those rims are pretty wide. Even with 28's, I'd recommend new tubes.