I ride Michelin City with reflective sidewalls + puncture resistance liner between casing. 28c rubber should fit that Cannondale. My 32c rear will last at least 12K miles. 28c rear with your weight should be good for at least 6K miles. Inflate between 85 and 90 psi. You'll notice a big improvement in ride quality over that 23c. Price is around $30 per tire. Get a pair to save $5 and shipping. JensonUSA ships tire in a full size cardboard box.

http://www.jensonusa.com/!8DcIJupCF7...ive-Strip-Tire