Wrong. We’re not talking about the appearance of the rider, who – because of the typical weight-craze that sooner or later seizes all riders and drives them bonkers for both their bike and their own size – is rather homologated and prone to thinness. We’re talking about the racing bike, which is more beautiful and therefore good if it weighs more in only one case, downhill.
The grimpeurs, those who tackle the climbs on 7-kilogram bikes, know this well: After a long climb there is always a descent to deal with, and the higher you go the more challenging the climb will be. With very light bikes the descents are more difficult, because the bike is less stable, you must ride “muscularly”, with your body contracted, tight to the limit for being so light so as to compensate for the lack of rigidity of the frame-wheel assembly.