I’m in need of a new tire for my truck. It’s been flat for a while.. but not worried about it as I ride my motorcycle alot anyways. Its starting to get cold and possibly icy, so it’s time to fix up the truck for driving safely.
Here’s some research on tires and what those numbers mean on the sides.. (I found it while looking over at: http://www.ehow.com/how_107557_choose-tires.html)

Step 1 Look at your tire label. It should look something like this: P185/60R 14 82H

Step 2 Buy for a passenger car. In the tire label, “P” indicates passenger-car tire. Other variations are “LT” for light truck and “T” for temporary or spare tire.

Step 3 Determine how wide your tires can be. Different cars can fit different sizes. The “185” in our example is the section width of the tire in millimeters. Shorter and narrower tires have lower numbers.

Step 4 Understand the tire type. In this case it’s a radial tire, as shown with the “R.”

Step 5 Figure out how to determine if the tire can fit your wheel rim. The wheel rim in this tire is 14 inches in diameter, indicated by the number after the tire-type symbol.

Step 6 Here, 82 is this tire’s load index, according to the industry standard Maximum Load-Carrying Capacity chart. This tire will safely bear 1,047 lbs. (475 kg). Four of these tires can carry a fully loaded car weighing a maximum of 4,188 lbs. (1,900 kg).

Step 7 The last letter (H in this example) is the speed rating: Q (99 mph/159 km per hour), S (112 mph/180 kph), T (118 mph/190 kph), U (124 mph/200 kph), H (130 mph/209 kph), V (up to 149 mph/240 kph), Z (more than 149mph/240 kph), W (168 mph/270 kph), Y (186 mph/299 kph). Speed-rating letters indicate the maximum safe speed the tire is capable of carrying under ideal conditions, for an extended period of driving. You might not feel a difference between riding on T-rated tires and H-rated tires, but you’ll save money on the former.