from 16 to 17or18 inch !.....M3
 

Hello every one !!
I got the 2007 M3 ….and it came with the 16inch rims…and am thinking to go for the 17 or 18 !! but I guess more of the 17 ! But I have no idea if this will effect the car or harm it in any how??? so what do you think ????

You can go with most any size wheel as long as the OUTSIDE diameter of the tire stays the same. A good place to look is Tirerack.com. The larger wheels (17, 18) will improve handling to some degree and will look cool, but remember that there are some trade-offs. Lower profile tires usually wear out more quickly, are more expensive, and expose your (expensive) wheels to damage because there is less rubber to absorb the slam from a pot hole hit. They usually do not do as well for winter driving, either, because of the larger width.

Don't forget to select a wheel with the proper offset and bolt pattern if you go with a non-Mazda wheel. This is important for alignment and handling amog other things. Most good wheel dealers will help you select the right wheels/tires for your car.

I doubt it will affect anything that negatively. Just make sure your lugs are the same pattern and that your clearance between the tires and the wheel well is ok. You'll need to get a new set of tires to fit the increase in rim size. I had over-sized tires on my old truck that made my speed register 5mph slower than I was actually going, but if you buy tires with the same tire radius as your stock tires, should be ok.

My 2007 Mazda3 came with 205/50/17's, but I don't know if the switch from your 16's will affect your speedo.

RE: from 16 to 17or18 inch !.....M3
 

...And you may lose your tire pressure monitoring feature too, if you have it.

Here's a handy tool to calculate the speedometer variation when changing wheel/tire sizes.

http://www.miata.net/garage/tirecalc.html