whats the calculation to work out the capacity your rear mech needs (long, medium or small cage) based on casette rings & chainrings? there was a handy website that expained it all somewhere?
So if Ive got 52-30 chainrings and a 12-25 cassette, is it:
52-30 = 22
25-12 = 13
22-13 = 9? so my mech needs a capacity of 9?
Its something like that, but I think Ive got it the wrong way round?