From the FAQ on the Main Page (by Raistlen)
Stock Altimas's (1st gen) come with 205x60x15's
Stock Altima's (2nd gen) come with 195x65x15's
-The first number is the width of the tire from side to side
-The second number is the height from outside of rim to outside of tire.
-The third number is the diameter of the rim.
Rules: For every inch you increase the rim size:
-add 10 to the first number
-subtract 10 from the middle number
(ie: (1st gens) going to 16's technically call for 215x50x16, going to 17's technically call for 225x40x17)
(ie: (2nd gens) going to 16's technically call for 205x55x16, going to 17's technically call for 215x45x17)
This keeps to the rule of same diameter wheel/tire as to not throw off the speedy to much.
Now there are occasions in which you just can't or don't want to stick to this rule. The bigger rim you have, the better your ride will look, the lower profile tire you will have, the worse ride/tire problems/price you will pay. From my experience, when you get into below 40 series tires, you feel every bump you hit, and you risk tire separation from our beloved city streets and highways. I started with 215x40x17's as that was all that was available that day, and of course, I had to have it. I ruined the two left by hitting those big city bubbles within 3 months. Good thing I got the full replacement certificate. Not even a full year after I had those tires, I was back at the shop replacing them with 225x45x17's. I should have been 225 to begin with so I got it right, but I choose 45 series to get just those few extra mm's of meat. To me... it has made a huge improvement on my riding experience, not too mention, they just look that much more aggressive.
Reminder: The thicker the tire (205/55/16), the nicer and more comfy your ride will feel. When you get a size lower than that (50-45-40 etc), the ride becomes more "bumpy" but your handling improves. So it's kind of a win lose situation.
When going to 18's, I have heard of people using 235x35x18's, but I am not sure as to their experience or pleasure with them. Hopefully, some of you guys with 18's can give some input on your tire sizes and how you like them. If 235's work with no problem, I will happily jump up to a 235x45x17 just to put that much more meat down to grip the road. -Raistlen
Originally posted by ThurzNite
The Bolt Pattern for First and Second Gens (93-01) 4 X 114.3
Originally posted by Altimat
The Bolt Pattern for Third Gens (2002+) is 5 X 114.3
Tire calculator: http://www.miata.net/garage/tirecalc.html
I think this info (there's more I'm missing) should be a sticky in this forum.