Yes I’ve changed to 520 without changing gearing. And with all due respect your OPINION with no direct experience that 2-3 pounds of rotating mass reduction makes no difference is just that, an un-experienced opinion, I have direct personal experience with doing so. 2 to 3 lbs IS noticeable.
Also, between rotors, wheels, chains, Sprocket carriers, wheel nuts, titanium axles, titanium hardware through the entire wheel and rotating brake assemblies I removed 12 to 15 pounds of rotating mass off my last V4…that was a night and day difference in bike feel.
Now you next argument will be ‘maybe 12 to 15 pounds makes a difference but not 2-3 pounds’, but then you will argue against each of the mods that in aggregate get you to 15 pounds saying each one makes no difference.
And then you next argument after that will be “but that 15 pounds doesn’t make you faster”
Which we’ve already established is a really stupid argument to make for any riders at our levels, because NO MODS make riders at our levels faster.
Certain mods can make the bike FEEL a lot better though…and after ergos and a correct suspension tune…reducing rotational mass is at the very top of THAT list.
Also, while reduced rotational mass may not make your fastest lap time much faster, it certainly makes the average lap times of your last two sessions of the day faster, because 15 pounds of reduced rotating mass feels like at least 50 pounds of reduced gyroscopic forces that you are fighting against every time you flip the bike from side to said on every corner for the whole day, so by the end of the day you’ve worked way less hard.