What tire size should I choose?

Here is how to read/calculate tire size.

215/40ZR17

215 is the section with in mm. this tire is 215mm wide.
40 is the aspect ratio. 40% of 215 or 86mm is the height f the tire.
ZR is the speed rating
17 is the size of the rim

With this info you can calculate the height of any tire/wheel combo. Some manufacturers deviate a little from these specs hence there is some (minimal) deviation from manufacturer to manuf.

Specification	Sidewall	Radius	Diameter	Circumference	Revolutions	Difference
205/55-16	4.4 in	12.4 in	24.9 in	78.2 in	811 / mile	0.0%
225/50-16	4.4 in	12.4 in	24.9 in	78.1 in	811 / mile	-0.1%
245/45-16	4.3 in	12.3 in	24.7 in	77.5 in	817 / mile	-0.8%
205/50-17	4.0 in	12.5 in	25.1 in	78.8 in	804 / mile	0.8%
225/45-17	4.0 in	12.5 in	25.0 in	78.5 in	808 / mile	0.4%
245/40-17	3.9 in	12.4 in	24.7 in	77.6 in	816 / mile	-0.6%
205/45-18	3.6 in	12.6 in	25.3 in	79.4 in	798 / mile	1.6%
225/40-18	3.5 in	12.5 in	25.1 in	78.8 in	804 / mile	0.8%
245/35-18	3.4 in	12.4 in	24.8 in	77.8 in	815 / mile	-0.5%

I have found the following table to be extremely useful when considering new wheel/tire combinations for my 1995 240SX: (You can play with this stuff yourself at http://powerdog.com/tiresize.cgi)

Many have squeezed 225/50/15 on the aluminum rims with lowering springs and no rubbing problems. 215's should be no problem, but the profile should be dropped to improve handling and maintaining the speedometer calibration. I've put 205/50 on, but this is smaller than stock
diameter. 215/50 should come very close to the stock diameter. I personally prefer the Dunlop D40M2, but 215s aren't offered in the
D40M2. I think the SP8000s have a 215/50/15 for $139/tire. The Dunlops seem to stick well for the money, but don't expect some 80,000 mile tires. If you're driving the car to take advantage of the suspension
and existing power, bag the recommended tire stuff in the glove compartment. I recommend playing with the tire sizes and pressures to
maximize your personal type of driving.

Alex Gutarin wrote:
>
> I've just gotten a flat and it looks like I will be buying a new pair of
> tires for the rear wheels of my car. I wonder if it will take 215s... I've
> got 195s (that's what I had when I bought it), and the little thingie in the
> glove compartment says that it should have 195s in front and 205s in
> the back. Also, what kind of tires would you recommend? I was told
> that Yokohama's are ok, and my friend has Daytonas on his 240.

Rating Max Speed (mph)
Q             99
S            112
T            118
H           130
V           149
W          168
ZR over 149