Shimano Centeron and narrow pulleys
Just a note for anyone else who ever takes apart their Shimano Sora rear derailleur (or derailer) and is having trouble putting it back together properly because the parts are labelled with weird names:
"Centeron" pulley = upper or guide pulley.
"Narrow" pulley = lower or tension pulley.
I found the answer here. Thank you Shimano for inventing your very own terminology and not using that terminology in your documentation. (I get sarcastic when I'm frustrated.)
Isn’t Shimano notorious for inventing their own everything? I remember that when I was building a bike out of spare parts, Shimano ones stubbornly refused to work with anything else.
Yeah, every Shimano part comes with a pamphlet listing the Shimano parts it works "best" with.