Knees...

hippy Still, if you don't often ride that distance you won't tend to notice the bits that start to hurt..
Is your fix setup different from your other bike/s?
48x18 is fine.
Where does your knee hurt?

My other bikes are mtbs, so a bit different, and they hurt a little, it feels like behind the knee cap.

Maybe I'll try moving the saddle back a bit and see after a slightly shorter ride.

cheers!