My poor tandem has been neglected for while so now it's needing chain, cassette, chainrings and shifters. Seems like a good opportunity to move from 8 to 9 or 10. I've done a bunch of googling and think I get most of it but I've still a couple of questions.
What I get (I think)
Cassette: 9/10 should fit without problems as I have a hyperglide C hub and 135mm spacing
Rear mech: I can keep it if I want to go 9 speed but need to change it for 10 speed because of the change of pull on 10 speed.
Front mech: Might get away with it for 9 but would need a new one for 10 because of the change of chain width.
Now what I don't know:
Chainring spacing: What I have looks like 7.5mm and the 10speed I have looks like 7.5mm. Can anyone confirm that this is correct as I've seen some people suggest it should be 5mm? I'd like to just put on new rings as new tandem cranks are a pain to find and not cheap.
10 speed chain direction: As I understand it 10 speed chains are directional. I presume then that the left hand 'sync' chain would still rotate in the same direction as the right hand chain or does it make no difference as there is no mech to deal with?