I am trying to understand the physics of bike weight. I have just made a switch from an 11Kg road bike to an 8Kg one (obviously there are many more factors and differences between the 2 bikes other than weight), and have noticed the benefit of reduced weight. However I am not sure I understand it.
Let's say for example My combined weight is 8+75 for a total weight of 83Kg. The difference between this and 86Kg is minimal, but is does make a difference seemingly beyond what I would expect.
Assuming I could equalise the total weight by carrying a pack or particularly heavy bidon/saddle pack) such that the combined weight could be the same, why is the lighter bike always seemingly faster?
I have read something about rotational mass, which seems to indicate that it's nothing to do so much with your combined weight as perceived through gravity, but with the equivalent lifting effort of the moving parts, namely your wheels, and in fact it's wheel weight that is the major factor because your are in effect having to lift half the wheel in order to produce forward momentum. Is this a sort of gyroscopic affect whereby the easier it is to turn your wheel the faster you go?