My shim was obtained from my LBS who had the 1mm thick shim in stock. I have been riding my other bikes recently and not the Nano, but it was ready to go and I rode it yesterday. Even as heavy as it is, it was not slower than my Swift or Brompton and seemed to soak up bumps fairly well. My 52/42 chainrings and 11-32 sprockets were certainly good enough for my ride. At less than 1/2 the price of a new Swift, or 1/4 of my Brompton, I think they are an excellent way to sample the joys of small wheel riding and tinkering.