What do all those numbers on the side of the tire mean? Lets examine a tire for 2004 Chevy Trailblazer. This particular tire is a Goodyear Fortera P245/65R17 105S. The letter “P” is designated as a passenger car tire. The other possibility would be an LT or light truck tire. 245 is the width of the tire in millimeters or about 9.6 inches. 65 is the percentage of tire that is sidewall. A 70 series tire has more sidewall and rides softer than a 50 series tires. The 50 series tire will have less side wall flex and corner better than the 70 series tire but the ride will be rougher. R designates radial construction. 17 is the rim diameter in inches. The load index of 105 indicates that this tire can support up to 2039 pounds. Load index ratings range from 71 or 761 pounds to 110 or 2337 pounds. Lastly, the S is a speed rating of 112 miles per hour. Speed ratings range from L at 75 miles per hour to Y at 186 miles per hour.
What this means to the everyday driver is that you cannot mix and match. Changing sizes can distort speedometer readings which in turn could change shift points controlled by the vehicle computer. Changing sizes can also cause the tires to rub the body or frame. Uneven wear or mixing sizes can cause poor ride or bind the drive train on all wheel drive or 4 wheel drive vehicles.
Load ratings and speed ratings are important too. Not matching the original ratings could cause the tires to wear faster or even cause a blowout. When buying tires make sure the construction date is no older than 2 years old. Every tire has a build date. This is the last 4 digits of the DOT label. The Forteras I have in stock are dated 0612 or June 2012.
Whether you are looking for the right tires for your vehicle or they are just in need of basic maintenance, Innovative Autocare can help with all of your auto repair needs. Just give us a call or click here to schedule an appointment.