unsprung weight is bad. because it is unsprung.
more specifically? it is the stuff that rattles the wheel of your car / bike / etc even though all these expensive suspension components are doing their very best to keep the wheels where they are supposed to be, i.e. on the ground. the reason is that it is precisely on the wrong side of the suspension, i.e. the wheel.

unsprung_2

you see it is crucial to reduce unsprung weight as much as possible.
every gramm counts.

unsprung_1

et voila! 137 grams just by changing a cassette? yep.
thanks spesh for kitting out the enduro with the cheapest and heaviest components in mountain bike universe. that was probably the easiest 137 grams i have ever shed. plus it was trying to chew on my favourite hope hub.

i am kidding of course. unsprung weight is not that important. it is revolving weight … 😉

then there is of course this crappy front derailleur, pretty unreliable if you ask me …