When
you choose or care for your tires, the meaning of those numbers on
the sidewall is important to know. Each of those numbers and ratings
indicates the manufacturer's minimum recommendations for your
vehicle. Here is a basic key to those numbers to better help you
understand your tires' limits and give you an idea on what to buy
when you need new ones.
Size
Information
Tire
size is one of the most important things to consider when you choose
a tire because you want tires the fit and don't rub against your
car's fender. When you look at your tire's sidewall, size information
is most often expressed as something similar to P215/70R15. Here's
how each number and letter in the size marking breaks down:
-
P refers
to tires designed for a passenger car. For light trucks, the
letters LT would
be in that spot instead.
-
215 refers
to width of the tire in millimeters.
-
70
refers
to the aspect ratio that determines the height in relation to the
width. In this case, it is 70 percent of 215. Usually, the larger
the number, the taller the tire.
-
R
means
that it is a radial tire.
-
15 is
the actual rim, or wheel, size. The tire must have the right rim
size in order to seal properly.
You
need to know the size of your tires to ensure that any replacement
tires will also fit on your vehicle. Vehicles only have so much
wiggle room when it comes to tire size.
Load
Index and Speed Rating
The
next large numbers that you can see on your tire are the load and
speed rating. These ratings are often listed as a number and letter,
such as 85S. The 85 refers to a specific load index, or the amount of
weight that the tire can handle. The higher the load index, the more
weight the tire can handle.
The
S next to the load rating refers to the maximum sustained speed that
your tire can ideally handle. Most speed ratings range from 75 to 150
miles per hour. The available passenger car and light truck letter
ratings are, from low to high, Q, R, S, T, U, H, and V. There are
special W, Y, and Z ratings for exotic sports cars. Your technician
can further explain your specific tire speed ratings for you.
Treadwear
and Traction Rating
Treadwear
and traction ratings are listed in smaller, less noticeable letters
above the tire size and load ratings, but below the tread. These
ratings indicate the expected amount of wear time for your tire.
Passenger car and light truck tires should have between a 200 and 600
treadwear rating, with most falling around the middle range.
Traction
ratings range from AA to C with AA being the highest rating. Traction
ratings refer to the amount of grip, or traction, the tire has on the
road. Most tires are rated A and provide good all-around traction for
most vehicles.
Maximum
and Recommended Pressure
You
may see that there is a maximum tire pressure rating on your tire's
sidewall as well. However, you should never inflate your tire to that
number or you will experience a blowout. Instead, look for the
recommended tire pressure on the label inside your front door. Tire
pressure should be listed for both front and back tires.
Your
manufacturer's recommended tire size, type, and pressure are based on
the ideal ratio and rating for your vehicle. It is important that you
never go below the manufacturer's ratings for safety reasons.
However, in some cases, you can exceed tire quality and size ratings
as long as you don't go too large for your vehicle.
When
you're ready to shop for new tires, Radial
Tire Service can
help you pick out the right ones for your passenger car or light
truck. We will work with you to make sure that your tires work well
with your vehicle and give you the performance that you need. Contact
us or come in to see what we can do for you.
