Here is the weights of the new Shimano 105 5800. The new 105 have inherited many of evolutions of Dura Ace and Ultegra. It notably receives a 4 arm crankset, 11 speeds setup, and new chain surface treatment.
The new shifters weight 490g, with only two grams separating left and right lever. This is approximatively the same weight of the 5700. A screw allows for lever reach adjustement.
The 11 speed cassette in 11-28 weights 277g, and the CN-HG600 (116 links), with the new Sil-Tec treatment weights 266g.
The rear derailleur, with short cage, weights 228g. The front one weights 89g. So on the derailleurs side, we don’t earn much compared to the 5700…
The crankset, with 172,5mm cranks, and two lovely 50-34 plates, wieghts 734g.
The 105 bottom bracked shows a quite tiny weight for this type of bottom bracket : 76g.
La The brake callipers weighs 389g. By comparison, a Sram Apex pair weighs less than 310g… They accept tires up to 28mm wide.