I've got Panaracer Pasela TG 700x28 tires on my De Bernardi steel frame. It's a tight fit, and I have to let most of the air out of the tires to clear the brakes, but they fit fine once you get the wheels mounted. I haven't tried the Panaracers on my Eddy Merckx frames, but I am sure they would fit because they have slacker angles and more room behind the seat tube than my DeBe. I've put Michelin 700x25s on both of my Merckx frames in the rear, and they fit fine once you clear the brake calipers. Michelin 25s are actually 27 mm wide.