Converting impala's 16' to 15 inch rims

Has anyone out there changed there 16 inch rims to 15 inch rims and tires,if so how,tried to do it but the 15's would'nt fit over the front calipers but would fit on the back,does anyone know what to do to make them fit the front,shave down the top of the front calipers maybe,if so how much,it only needs a hairline shaved off to make the rim fit,how about changeing the front calipers of of the 90-99 chev luminas,anyone know if that will work,a smaller tire and rim on these impalas will make them ride twice as good,better gas mileage,also better in the snow from a 60 series tire to a 70 or 75, now i thought about changing the tires they come with which are 225/60/16 to a 215/65/60,that should make her better on gas ride better and be better in the snow because the tire is narrower and higher,has anyone got the 215/65/16's on their impala,if so what difference did you find,better on gas,better ride, there is also another tire 205/70/16,does anyone know if this will fit the impala or will the tire strike the bottoms of the strut base,anyone with any solutions for a different size tire for the impala to make her better on gas,ride better,plese let me know if you changed you tire and rim size to what size and the difference it makes to your car,thanks