The first pair I tried, I ran them twice for 5min @ 3v and it barely wore down the serations. So I used the motor on a practice day where I was just running laps trying to hit the correct lines but not trying set the track record. After a couple of packs the brushes broke in nicely. I then just cut the comm and the motor was ready for race day. The hard silver springs are what is usually recommended for Sedan.