18" rims to 20" rims will they work ? 2009 Titan

They will fit just fine as long as your tires arent too big or anything. You will also need to look into getting a wheel with the correct offset and all of that but I'm not the guy to ask about that stuff. And you can have your speedometer calibrated but you have to buy a separate unit in order to do it. If your going to keep your suspension stock its probably not worth getting the speedometer thing because you wont be able to get a large enough tire to make the difference between stock and new large enough to make the calibration really necessary. I use this website all the time, just plug in your stock tire size and your new tire size and at the bottom it will even show you how off your speedometer will be. You'll see that its probably not very much. http://www.miata.net/garage/tirecalc.html

If you could tell us the wheels you are wanting to put on and the tire size you are looking at we would be able to tell you if it will work.