Step1
Understand What a Car Tire Ratings Placard Is.
Many people get tripped up by this. The placard is on the car not the car tire. You need to read the car tire placard on the car to determine the tires specified for your car and the proper tire size, tire inflation and the tire load limits. Only then do you pick out the tires for your car.
Step2
Find the Tire Ratings Placard.
The NTHSA explains:
"You’ll find the label located inside the driver’s side doorframe or doorpost. It may also be affixed to the edge of the driver’s door or the inside of the glove-box door or trunk lid."
Step3
Tire Ratings - Traction grades
Traction grades are an indication of a tire's ability to stop on wet pavement. A higher graded tire should allow a car to stop on wet roads in a shorter distance than a tire with a lower grade. Traction is graded from highest to lowest as "AA", "A", "B", and "C".
Step4
Tire Ratings - Treadwear grades
Treadwear grades are an indication of a tire's relative wear rate. The higher the treadwear number is, the longer it should take for the tread to wear down.
A control tire is assigned a grade of 100. Other tires are compared to the control tire. For example, a tire grade of 200 should wear twice as long as the control tire.
Step5
Tire Ratings - Temperature grades
Temperature grades are an indication of a tire's resistance to heat. Sustained high temperature (for example, driving long distances in hot weather), can cause a tire to deteriorate, leading to blowouts and tread separation. From highest to lowest, a tire's resistance to heat is graded as “A”, “B”, or “C”.
Step6
Buy Tires
Hopefully with this car tire rating information in hand you will be able to get a move onto making an informed decision and a quality car tire buy. A few good links for finding car tires and comparing their tire ratings are The Tire Rack, Tires Easy and Safecar.
Tire Ratings Quick Giude
Novice 
