I just purchased some snow tires for my son's GF. The girlfriends mother wanted snowy's on her daughters car asap with the 3-4 inches of snow we received last night/this morning so since I was the chosen one to do this, I purchased some I found online but chose a different size tire/wheel. The winter tires/wheels with TPM's, (hopefully?) I bought came off a 2005 Malibu just like her car (exact same) but are 205-65-R15's compared to her current tires/wheels which are 215-60-R16's. How much difference in speed will she notice being as the tire is slightly smaller in diameter than what is currently on her car? As an aside, I got Nexen tires (which I believe are Cooper tires?) on stock Malibu rims and only paid 200 dollars for them. The tread is still healthy/deep, imo, as well.