I want to upgrade my wheel and tire package--but I want to
keep the speedo from being off--i have a 1989SE and I know the stock rubber and wheels are 205/65 r15 w/15in alloys...
would like to purchase OZ F1 Cup rims at either 17 or 18, also Pirelli P-zeros would like to know the best size tires for this type of maxima--i have a whole list of performance mods I would like to do--

 

To keep the same speedo reading, you need the same tire outside diameter (OD). Most of the manufacturers will list this data on their web sites.

 

You'll have no significant problems with gearing or speedo reading if the tire height stays within a half of an inch of the stock tire height. For every 1" larger diameter of wheel size, the sidewall size (aspect ratio) number decreases by a factor of 10. Ex 15" wheel with 65 series tire becomes a 16" wheel and 55 series tire. 17" with 45 series, and so on. Tire width is determined by the wheel width. Hope this helps.

 

Tire aspect ratio is defined as the tire cross section height (from bead to tread surface) divided by the cross section width (from sidewall to sidewall). For example, a 205/65R15 tire has a section width of 205mm, and a section height (approx) of 0.65 x 205, or 133.25mm (5.25"). Thus the approx tire OD is 15" (rim dia) + 2 x 5.25", or 25.5". This same calculation for size 205/55R16 gives OD of 24.9", but a 215/55R16 would be 25.3", which is closer to your original size. A tire with a given section width may be used on a range of rim widths, which is determined by the Tire & Rim Association here in the USA. Again, all of this data is available from the tire manufacturers, usually on their web sites. Hope this helps you out.