Ok, I've read SB's tyre sizing, and learned a bit, but I'm unsure whether the tyres on my wife's (now spare ) bike are interchangeable with mine :?: . She has 26x1.6 (41 559) and I have 26x2.0 (54 559). I know the diameter is the same, but I wonder at the difference in width...? Should I be out there measuring the rim widths..? Any knowledgeable soul able to put me right..?