Hi im new to the forums list and i would just like to ask a question that has been bothering me for a while. What tire size whould i use for 16 and/or 17 inch rims that will have the same diameter as the original tires and keep the speedometer accurate? By the way i have a 1987 maxima GXE

No Problem.

For 17" Wheels cop yourself with: 205/45-17 tires
that size will fit ya ride and keep in tact with the diameter.
I know because I sport 'em in my Max.
There are different brands and styles, so look into what benefits ya.
Falken and Yokohama are excellent choices.

Peace.

For 16": 205/55-16
For 17": 205/45-17

Here are some links to help you

http://www.miata.net/garage/tirecalc.html
http://www.c5-corvette.com/tirecalc.htm