In F1 The track width is normally measured to the centreline of the tyre. If the front tyres are narrower than the rears, but at the same time you are exploiting the maximum width available - then the front track will be wider than the rear (but not necessariliy the overall width of the front). read more
Widening the front track (the wider tracked end of the car) will predominantly increase the load on the inside rear tire, but the transfer will be relatively less effective then changing the rear track. read more