If the new calipers don't work, i.e. don't have a long enough slot, you should measure the reach that you need before purchasing another set. Put a ruler on the center of the bolt that goes through the frame and measure down to the center of the rim's braking surface. This will tell you the reach your frame/rim combo requires. Brakes will specify their reach in millimeters, so a millimeter ruler is helpful, unless you like doing the math.