I started commuting to work 2-3 times a week. I took a spill my very first day and am still a little overanxious when riding down a hill. My problem is that when I am going down a steep hill (and I have a few on my commute) I occasionally have my rear brake slip when I apply it. Pumping my brakes has worked to slow my bike when this happens, but it is freaking me out.
I am riding on a dry, smooth road so what would cause the brakes to slip?