“Man, Brake set-up is hard”

Setting up a rim brake correctly can be challenging, especially when you’ve been working without any standards. Sometimes you get ‘em to work awesome, some you shouldn’t have even touched. What makes the difference?

Factors.
Frame quality- a more flexible frame reduces your braking power.
Caliper and lever quality- lower quality parts will be less stiff and have looser bushings.
Cable quality- stiffer outer housing and smoother inner wires give a better response.
Pad quality- generally a softer or more abrasive pad will stop better.
Any of these factors can be argued to death, but let's use these as a starting point.

Set-up.
Would you prefer a trained Surgeon, or a 10 yr old child to set a broken arm? A mechanic that has gone through any of our training will be able to understand how to set a brake up to stop to it’s best performance. We need to set the pad to caliper arm positioning so that the pad has the most compression force to the rim. Because there is frame flex and bushing play in almost every caliper arm, we must set the pad so the front edge contacts the rim first. If set this way, the rider will experience a steadily increasing response to greater lever pressure. The “toe-in” amount is suggested to be at a minimum, to reduce brake drag and give a better feel to the rider. Everyone has a different shaped hand, but some things are constant. The human hand can generate the most power when it is almost closed. Brake wires may stretch a bit, and pads will wear. To compensate for both factors we set the cable tension so that on a new bike, lever squeezed firmly, the lever does not come closer than parallel to the grip. This usually allows for a one to two millimeter gap between the rim and pad when the brake is released, for quiet coasting.

Well, yeah but…
Your first experiences at this may be difficult, but so are most first experiences. It takes work and determination to become a proficient mechanic; you must decide to do it until you are great. Evaluate your work, and when it does not meet the standards fix it. Some brakes will require more attention, but your instructors have the confidence that they can improve the braking performance of any bike on the planet. You should too, so come to class and keep at it!