25" 72' PX10 converted to 650B. This is just after the initial build, and some parts have changed since (tires, crank, bar, stem, and brake levers):



It originally came with tubular wheels of course so basically 700c. To reach 27" to 650b is a real stretch and it can be done to reach, but not many long reach brakes will work. I am using Tektro R556 brakes which are 55-73 reach. The front and rear pads are down toward the bottom of the adjustment (measured around 68-70mm if I remember correctly). For 27">650b you might need around 75-80mm or even more. Fenders shown in the picture are 700c Planet bike Cascadia plastic fenders.