I've been riding and daily commuting the same set of wheels for a while now with no issues till this past week.

While coming up to a light I will apply backward pressure on the pedals and feel a 'slip' in the drive-train of about 1/10th of a pedal roatation. This generally happens when I am nearly at a complete stop and have a good amount of my weight on the rear facing pedal. I ride with two brakes and use them so it is only within the last few feet of stopping that I am coming out of the seat....not skid stops for me.

When I start pedaling again I get same amount of slip, but this time when pressure is on the forward pedal. I do most of my starts and stop while standing on the pedals.

What I don't get is that I keep my cog/lockring tight. When I took everything apart it looked and felt like all the threads were in good working order. I've tested the threading any way I know and all seem to be in working order.

Could the cog width be too narrow or my lockring be a piece of poop? I ride more aggressively now than I ever did in the past (good things happen when you get back into shape) so I am not sure what I am doing to cause this.

UPDATE: 07/11/11 Problem solved.

I decided to tackle the issue again tonight after not getting any progress with the bike over the last couple of days. I did all sorts of tests to see why I couldn't get the cog to tighten down properly. I even did the riding up a hill and walking back down to tighten the cog and then going to town on the lockring. Nothing seemed to help. I went to far as to take video at the level of the cog and when there was slippage I couldn't see the cog move at all.

I was about to give up when I caught where the movement was coming from.....it was my f***ing chain ring bolts that were loose. It was just loose enough to slip an 1/8th of an inch in one direction or another from the center. I tightened those down and the problem was solved.