When shopping for tires, you need to
know what the numbers and letters on your sidewall mean in order to
select the appropriate replacement tire.
Tires usually follow a pattern can be illustrated in sidewall - For example
"Bridgestone Potenza RE040 205/50VR15 85V"
- Brand: Bridgestone
- This is the company that manufactured the tire.
- Series: Potenza
- Tire manufacturers often create a series of tires with somewhat
similar handling and performance characteristics. For example,
Bridgestone uses the Potenza name on many tires that may appeal to drivers who want a performance tire, and the Turanza name on many tires that are intended for less aggressive driving.
- Model: RE040
- This is a pretty specific identification number of the general performance characteristics of this tire, regardless of its
- Width: 205
- This number is the width of the tire in millimeters. This is the most important number to describe a tire's contact patch.
- For example, a 215-width,
17-inch tire may look great, but all things being equal, a 245-width,
15-inch tire will out-corner it every time, because the contact patch is
wider.
- Aspect ratio: 50
- This is the height of the sidewall from the rim to the tread, expressed as a percentage of the tread width.
- For example, if the tire is 205 mm wide, and its aspect ratio is
50, then the sidewall is about 102.5 mm tall (50 percent of 205 mm).
- Sidewall height is important for a number of reasons:
• As you move up to larger wheels, or down to
smaller ones, a corresponding change needs to happen in the sidewall
height of the tire in order for the rolling diameter of the wheel and
tire combination to be as close to stock as possible. This will ensure
the accuracy of your speedometer and prevent unwanted alignment changes.
• The sidewall height affects the turn-in feel (the responsiveness you feel at the steering wheel) and the ride quality.
• Lower aspect ratio (shorter sidewall)
provides better turn-in response than a higher aspect ratio, but at the
expense of less break-away warning and a more jarring ride — in extreme
cases, even exposing the wheels to potential bending and breaking damage
from potholes and other surface irregularities.
- Speed rating: VR (V-rated radial)
- In this case, V identifies a speed rating above 149 mph.
- The R means the tire is a radial. Virtually every new tire is a radial, unless you have a special tire for a classic car or a racing car.
- Load rating: 85V
- In this case, 85 means the tire is rated for 1,135 pounds. Multiply this by the number of tires on the car, and you get a
maximum safe loaded vehicle weight of 4,540 pounds (including people,
luggage, a full tank of gas, and all the loose change under the seats).
- The last V repeats the V speed rating.
I hope this piece of information will help you to read your tire sidewall. If you are still unsure then seek the help of a professional.