As I wrote in my first post, the front rim, where's the issue, is 700c alluminium one, the old one was Rigida Superchromix 27 inch steel rim, but there was almost no stopping with the MTB pads and the steel rim, so I moved on alluminium 700c to install narrower tire but this stopping problem is awfull. If it matters, my brake levers are Weinmann's too. They seemed to have a lot of "power" but this flexibility of the brake arms...