Hampton Roads Club Mini

This may be a silly question but I did two things to my MINI at the same time and now I get significantly less gas milage.

1) I put bigger/stickier tires on in. I went from the 195-55-16 Runflats to 225-45-17 Kuhmo MX tires. I did have to put 1/4 inch spacers on the front to clear the struts.

2) I took it to CF to have a front wheel bearing changed and for a scheduled check up.

When I picked it up from CF it seemed to have a little less umph and I'm down 50 miles per tank of gas. That seems to me a pretty big jump just for tires but before I took it back to the dealer I thought I'd ask you guys if you noticed anything when you up sized your tires. I just did the math and it comes out to about 4mpg.