I took two bikes to a race one day. One for a cat5 race and one for a masters 30+ 4/5 race.
One bike was a 1993 italian steel race bike with 700x23c tires weighing in at about 25lbs, the other one a Trek Madone 5.2 also with 700x23c tires weighing in a little over 18lbs.
Didn't make a lick of a difference, got dropped during both races and averaged about 20mph on the same track at the same day.
__________________
Gelato aficionado.