I drive a 08 Mazda 3. The stock wheels are 16" with 205/55/16 tires.
I have replaced the stock wheels with 17" wheels that came with 215/45/17 tires.
Its time to change my tires on the 17s and I want to upgrade from the 215/45 tire to a 225/45 tire. Will the 225/45 tires fit without rubbing?

 

It depends on the offset of the wheel, but plenty of people have fit 225 and wider under the fenders of a 3.

 

im not %100 sure, but I think the rims are 17x7 and the offset is 40

 

There should be a sticker inside the barrel of the wheel. It'll say "17x7 offset +40" if your wheels are 7" wide with a +40 offset. (The Mazda3 has a lug pattern 114.3x5 like the pic) If the sticker is gone or the info isn't stamped on the wheel, you can figure out the offset pretty easily. Definitely figure out the offset before you buy the wheels.

Linky to help figure out offset: https://www.rsracing.com/tech-wheel.html

Pic of typical sticker:

The wheel in the pic is 17x9 with an offset of +13 and a lug pattern of 114.3x5