ever decreasing tolerance
A couple of millimetres' difference makes all the difference, such as the tyre being able to rotate compared to the tyre (even a rather more worn one than the newish one I had been using up until Tuesday) being firmly wedged against the band attaching the front mech to the seatpost. It's a shame to have to give up the slight extra cobble-withstanding ability I've grown used to since I found a 25c tyre which would fit my stupid ill-measured frame but being able to move is the most important thing. It felt quite smooth on a wee test ride round the block and might even persuade me to change the front, too. Perhaps if it starts to feel sluggish in comparison I might. The other main thing is that I now have all the gears I'm supposed to have and have that new-bike feeling of a component working perfectly whenever I shift downwards, though It'll take me a wee while to get confident enough in the smoothness to fully hoick the shifter to shift upwards in one movement. I don't use rings other than the middle that often but having the ability to shift back up would have been handy on Sunday and Monday when the occasional bump managed to dislodge the chain from the middle onto the little where it then had to stay until I could be bothered to stop and shift it back by hand.