Upgrading an old classic: What modern components?
 

I am planning to change wheels,derailleurs,crank and gearing on my Dawes Galaxy to make it a more modern rider. I would like to use items which will fit without modifications to the frame. I also may wish to use the Weinmann brakes with new cables and pads, so what size wheels will match the original 27 x 1 1/4 closely enough to allow this?