The February issue of BMWcar magazine has an article by Jeff Daniels on p. 58
that warns about the hazards of making too great an increase in wheel size, width and tire width. He is especially critical of the move to 18, 19 and 20 inch wheels.
He also says that the increased turn in response is well beyond the ability of most drivers to exploit. He does say that if wider tyres and wheels are developed as part of a complete suspension package the effects are not so bad. If you want to subscribe to the magazine, here is an address in the U.S.
Eric Waiter Associates
250 U.S. Highway 22
Green Brook, N.J. 08812