I hope someone told you to make sure the brake shoes are toed in so when the friction tries rotating them they end up being more parallel to the rim under braking force. On my old junky ten-speeds I ride I carefully bend the brake arms so the trailing edge of the pad is about one-eighth of an inch off the rim when the front of the pad is just touching, but depending on the material your brakes arms are made of and their quality the amount of toe will vary.