Aside from the burning lungs and searing leg pain, one of my problems last Sunday was lack of rear wheel traction. On short steep hills, my wheel would start fishtailing and spinning out when I got out of the saddle to get more power. I was in what seemed to be the most friendly gear (39 x 27). My tire pressure was really low and there was no lack of tread (conti twisters). I sometimes have this problem when sprinting on the road as well. I stand up and ocassionally whip the back wheel around a little.
I'm pretty sure it's a problem of weight distribution. I need to stay back on the bike, but does anyone have suggestions for correcting this?