If you look really close at the rear stays on a UO8 or similar Peugeot you will notice that the chain stays are crimped to allow tire clearance. If, like most North American market UO8's, yours has 27" wheels you will notice that the tire sits a few millimeters past the widest point in the crimp. That's because it was designed for 700C to begin with. The 27" is just an adaptation for markets where 27" wheels/tires were standard. 700C will bolt right in a the standard brakes will adjust to a perfect fit as this is how the bike was originally designed in France. They didn't modify the frame to fit 27" wheels/tires.