Ford Mustang Owner's Manual page 204

Maintenance and Specifications
2. 215: Indicates the nominal width of the tire in
millimeters from sidewall edge to sidewall edge. In
general, the larger the number, the wider the tire.
3. 65: Indicates the aspect ratio which gives the
tire's ratio of height to width.
4. R: Indicates a "radial" type tire.
5. 15: Indicates the wheel or rim diameter in inches.
If you change your wheel size, you will have to
purchase new tires to match the new wheel
diameter.
6. 95: Indicates the tire's load index. It is an index
that relates to how much weight a tire can carry.
You may find this information in your owner's guide.
If not, contact a local tire dealer.
Note: You may not find this information on all tires
because it is not required by federal law.
7. H: Indicates the tire's speed rating. The speed
rating denotes the speed at which a tire is designed
to be driven for extended periods of time under a
standard condition of load and inflation pressure.
The tires on your vehicle may operate at different
conditions for load and inflation pressure. These
speed ratings may need to be adjusted for the
difference in conditions. The ratings range from
159 km/h (99 mph) to 299 km/h (186 mph). These
ratings are listed in the following chart.
Note: You may not find this information on all tires
because it is not required by federal law.
Letter rating
Q
R
S
T
U
H
V
W
204
2004 Mustang (mus)
Owners Guide (post-2002-fmt)
USA English (fus)
Speed rating - km/h (mph)
159 km/h (99 mph)
171 km/h (106 mph)
180 km/h (112 mph)
190 km/h (118 mph)
200 km/h (124 mph)
210 km/h (130 mph)
240 km/h (149 mph)
270 km/h (168 mph)