Hi, I'm looking at doing the same operation, specifically with Tiagra BR-4500 model brakes.
According to
here it states the brakes have a 49mm reach. Does that mean the pivot bolt extends beyond the brake calipers by 49mm? Meaning there is 49mm of bolt to cross through the fork or frame ? In that case, would it be long enough to fit a regular old 12 speed from the 80's (Fuji DelRey) ?
Many thanks for your help
Steven