Originally Posted by Jamie Corrado
I use a pretty long break-in to seat the brushes fully. Then once I notice the serrations are almost gone on the positive side(heavier tension) I rebuild which is usually around 2-3 runs after the break-in.
Well that explains a lot. Not to get too far into a motor discussion, but you might be abusing and using up your brushes before you ever get to the track. To me, a 767 is one of the longer lasting, high performance brush I have used. I get 6-8 4-cell runs on a set of brushes and the serrations aren't even gone. 200 seconds at 2 amps with a com drop on each brush is all you need for a 767 to work perfectly on a fresh cut com.
Maybe it's just me, but your type of maintenance isn't normal with a 767 Reedy brush.