I wanna upgrade rims and tires from the stock 16's which I think has 265/75 tires on it?????

anyways, can anyone tell me what tire for a 18, a 20, and a 22 inch rim will I need to get in order to stay at the same stock diameter? or slightly smaller is ok. But please not larger.

 

Here's two resources for this sort of thing:

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

enter stock tire, and new tire size...and it will give you all the info regarding the differences between the two.



http://www.dakota-truck.net/TIRECALC/tirecalc.html

similar, but gives your more options....follow the directions at the bootom and you can get all the various options for your rims and the details of how much bigger/smaller the tires would be, speedo changes etc...

best of luck