I bought 25. The tire 700 x 23C is too small in Paris. It is often stuck in sewer or subway gratings. 28 is too large to go fast on the asphalt. I think 25 is a good compromise when riding in town. Then the tire is rather light (compared to my old tires Schwalbe Durano Plus which are also excellent tires in other circumstances). As for the specifications of this tire, I can not teach you anything. I'm not an engineer. But since the purchase, I do not know any braking problem, puncture or other. I am fully satisfied.