Assuming the comm is over 0.270" in diameter at it's smallest (most worn portion of the brush track), it should be possible to true it up on a comm lathe. If it's less than that, there isn't enough copper left to allow it to be trued, and it will have to be replaced...
Does that help?
"If you cannot win, make the one ahead of you break the record."
Biff Racing Team #420 (Ah... The "good old days"...)
The local indoor Offroad Track: The RC Race Barn
TLR22-3.0, TLR22T-2.0, TLR22SCT-1.0