You can definitely notice 2 lbs + butted tubing upgrade while riding a bike. It's essentially why Raleigh offered 3 grades of steel bikes in the 70s : 28 lbs

You can definitely notice 2 lbs + butted tubing upgrade while riding a bike. It's essentially why Raleigh offered 3 grades of steel bikes in the 70s : 28 lbs : carbon steel (2 models) 25 lbs : 531 butted main tubes, forks (2 models) 23 lbs : 531 throughout (2 models) The super course was a bit of an aberration (27 lbs; 531 plain gauge steel main tubes only; only a 1 lbs upgrade from carbon steel; the 531 did not improve the bike but the sticker on the seat tube conferred bragging rights!)