"This wheel works well."
Translation:Tiu ĉi rado funkcias bone.
I realize this is a year late, but it's the top question and has no answer yet.
Tio replaces a noun and can stand alone. Tiu can not stand alone.
So, in your example, "Kies plumo estas tio?" The "tio" is a noun representing the pen right in front of you.
Tiu is always with a noun. So, "That pen is beautiful" is "Tiu plumo estas bela" because the word "that" isn't a noun and isn't replacing anything.
I don't think that's correct. If it's modifying a noun, it has to be tiu, but tiu can stand alone with the meaning "that one". Kies plumo estas tiu? is a valid sentence if you're singling out one pen from a group. (I think.) Though perhaps in that case one can think of the noun as being implied: Kies plumo estas tiu [plumo]?