Below you can see a major difference in the rim, on the right side is the brake pad residue encrusted surface. On the left is the newly re-surfaced side. We use a special Mavic rim stone to re-surface the entire rim followed by a cleaning from some rubbing alcohol. This will greatly increase your breaking power and lengthen your brake pad life. This is a very good thing to do, your bike will love you for it. It is especially important for bikes that get ridden in nasty conditions. Let us know next time your bike is in and we can do this for you.