Sport Truck Tire Guide - Reading Wall Writing - Tire Talk

  |   custom Sport Truck Tire Guide tire Sidewall Markings Do you remember the old tire commercial where the customer tells the tire salesman, "the ones, like the ones on my car"? Understanding your purchase is the first step in making the best choice. The sidewall is essentially the owner's manual of that tire. We'll give you a play by play on what these markings are and what they identify. We hope this information will help you see the writing on the sidewall with new insight. There are many different ways a tire can be marked on a passenger and light-duty truck: P-Metric, Metric, European Metric, Millimetric, and Alpha-Numeric. Some tire manufactures have special markings for light-duty trucks, such as Light Truck Metric, Light Truck High Flotation, and Light Truck Numeric. Not to worry; they all say the same basic thing, just in different ways. To familiarize you with the different types of ID marks, we'll go over them one at a time, although you probably won't be buying any European Metric tires, so we'll skip over them. P-Metric example: P215/65R15 95SP= Passenger car215= Section width measured in millimeters65= Aspect ratio (which means the sidewall height is 65 percent of the section width)R= Radial carcass construction15= Rim diameter95= Load indexS= Speed rating Metric example: 305/45R22 118V305= Section width measured in millimeters45= Aspect ratio (which means the sidewall height is 65percent of the section width)R= Radial carcass construction22= Rim diameter118= Load indexV= Speed rating Millimetric example: 240/55R390240= Section width measured in millimeters55= Aspect ratio (which means the sidewall height is 55 percent of the section width)R= Radial carcass construction390= Rim diameter in millimeters Alpha-Numeric example: BR60-13B= Load carrying capacityR= Radial carcass construction60= Aspect ratio (which means the sidewall height is 60 percent of the section width)13= Rim diameter Light Truck Metric example: LT235/75R15/CLT= Light truck235= Section width measured in millimeters75= Aspect ratio (which means the sidewall height is 75 percent of the section width)R= Radial carcass construction15= Rim diameterC= Load range Light Truck High Flotation example: 35x12.50R15 LT 113Q35= Overall tire diameter measured in inches12.50= Section width measured in inchesR= Radial carcass construction (if there is no R, it is bias-ply construction)15= Rim diameter (inches)LT= Light truck113= Load rangeQ= Speed rating Light Truck Numeric example: 9.50R16.5LT/D9.50= Section width measured in inchesR= Radial carcass construction16.5= Rim diameter (inches)LT= Light truckD= Load range Note:When you're replacing tires, make sure you check the vehicle manufacturer's suggested sizes and ratings. Remember that in some cases, more is not always better. A tire with a higher speed rating may have the capability to go faster than your vehicle, but it's very likely softer and will wear faster. Some tire shops will try to tell you it's OK to replace a tire with one that has a higher load rating than you need, but it will have a stiffer wall and more than likely the ride quality will inherently suffer. All in all, make a calculated decision on a tire. Get ready to replace it a little in advance. Waiting for a tire that had to be ordered is better than just putting the universal fitment the dealer keeps in stock. Reading and understanding are two different things. We'll break down the definition of the terms we used to identify the tire naming convention. Section Width is the measure of the tire's width at its widest point. With the tire mounted to the suggested rim, and at maximum air pressure, the sidewall of the tire will bulge slightly past the tread width. The distance between the two bulging sidewalls is known as section width. Aspect Ratio refers to sidewall height. The number that indicates the aspect ratio is given in a percentage. The percentage is a portion of the section width. For example, a 305/45R22's sidewall height is 45 percent of 305 millimeters. Carcass Construction will be either a radial or belted bias-ply construction. Rim Diameter is the diameter of the hole in the tire. This dictates which rim diameter the tire was designed to mount to. Load Index is used to reference the load index chart and dictates the maximum load the tire was designed to carry, at maximum pressure. The number 118 has a maximum payload of 2,910 pounds for that tire. In most cases you will only have two tires on an axle, giving you a 5,820-pound-per-axle rating or 11,640 pounds for a vehicle with four tires. Load rating is important because a tire with an insufficient rating for a given load will cause the tire carcass to distort, causing heat and potential tire failure. A tire with too much payload will have an extra ridged sidewall and the vehicle's ride quality will suffer. Speed Rating refers to the maximum tire speed. For example, a V rating has a maximum speed value of 149 mph. M+T, M/T, or M&T means the Rubber Manufacturers Association deems the tire to meet its mud and snow requirements. DOT, the Department of Transportation, must christen all tires sold in the USA. These marks signify that DOT deems the tire to meet safety standards for use on public highways. The numbers following DOT indicate general tire specifications. For example, DOT CXAF 77X3002 can be broken down to: CX= Manufacturer's plant codeAF= Tire size code77X= Brand and other significant information (optional)30= Week of the year (30th week)02= The year (2002)