My Challenge Parigi-Roubaix tires are pretty tight on my 700c CR-18s, even though they've loosened up after 1000 miles and a few dismounts for patching. It's no problem with my tire levers, though: dollar store flat-blade screwdrivers with the handles cut off and the rough edges "melted" on a die grinder (to prevent lever-induced pinch flats!).