Originally posted by ShadowAu
Both good suggestions but they don't explain why this happens after I have to change brushes and why only the positive shunt AND positive motor wire do it
I am running a pro 4 so both brush shunts are almost equal distance to the ground
AMGRacer is right... This is due to the brush getting hot. There are several reasons for this. There is more efficiency loss from the brush to the com then from the com to the brush. You should also notice that the positive brush wears more then the negative brush, for the same reason.
8 single will draw more torque/current down low then an 8 triple.
Mashing the throttle out of corners can contribute to this as well.
Running high silver content brushes will generate more current/heat.
Easiest way to fix this is to buy real solder, (not cheap shit), and solder the shunt on well, with a significant amount of solder to bond with the end-bell. A good blob of solder here will dissipate the heat better and will be more resilient to temperature.