Changing tire's specs... 17"
 

Please post what you know about this matter. Statistics, changes in MPG, traction, etc...

* 205/45/17 (OEM)
* 215/40/17 (Lower)
* 215/45/17 (Taller)

Would you get better or worst MPG by switching to a smaller or bigger tire?

Thanks

the differences are pretty minor at those changes. MPG is more affected by tire type, all season v. summer. A higher traction tire will decrease mileage over a tire that is made to last a bunch of miles at a loss of performance.

If you are that concerned about 1-2 MPG, then lay off the throttle ;)...that will save gas much more than a tire change.

Check the Tires, Wheels & Brakes forum. TONS of discussion there.
Otherwise 03indigo has it.
Not much change WRT tire height.
Traction much more influenced by tire compound than 5mm width.
Taller tire gets slightly better mileage, worse acceleration
Shorter tire gets slightly worse mileage, better acceleration

Paipuky. No offense intended here... but you might want to kick back with your favorite beverage and do some reading on this site. A lot of the questions you've posed recently have been discussed quite a bit in the past on this site.
Again, no offense intended. I just think it would be worth your time to read and read and read. I sat here for days reading back through the archived pages just to get a feel for the Mini and what to expect.
Check out the problems section, the wheels and tires section, and the modification section. All of them have some great info about your new car. :)