I show how to convert a mountain bike from 26″ to 700c wheels. The v-brakes didn’t reach the rims. So I played with installing two different devices to move the brake arms up. A Mavic adapter for 700c wheels, and a pair of brake post extenders. I could have converted to disc brakes also and avoided the adapters.
I took the bike out for a short test ride, and it rode great.
p.s. Another possible solution is to use “long distance adjustable V-brakes. I was pointed to them on ebay. The give a greater adjustment range for the brake pads and will allow them to move up that extra inch to reach the 700c rims. I haven’t tried them.
Source : RJ The Bike Guy