What Is the Difference Between 275/45R20 106V and 275/45R20 109V?

by Andy JosiahThe numbers 275/45R20 106V and 275/45R20 109V are two versions of the same tire size. Found on the tire's sidewall, the numbers represent a bit of information about the ring-shaped rubber covering around the wheel rim of an automobile; this is particularly essential for replacing and installing a tire. In this case, the only difference between the 275/45R20 106V tire and the 275/45R20 109V tire is the load index.

### Section Width

The first three numbers, "275," represent the tire's section width, which is the measurement -- in millimeters -- of the widest point of its outer sidewall to the widest point of its inner sidewall. So, that means that a 275/45R20 tire has a section width of 215 mm, which can be translated to 10.83 inches.

### Sidewall

The number "45" represents the sidewall aspect ratio, which is the ratio of the tire size's sidewall -- measured from the wheel rim to the tire tread -- to the section width. This indicator is expressed as a percentage, thus meaning that the 275/45R20 tire has a sidewall that is 45 percent of its section width. As for the sidewall itself, its height can be measured by multiplying the section width by the aspect ratio. Thus, the 275/45R20 tire has a sidewall height of 123.75 mm, or 4.87 inches.

### Construction and Tire/Wheel Diameter

The "R" after the sidewall digits indicated that the 275/45R20 is a radial tire. This means that it was made with the tire's cord plies "radiating" from the wheel's center, or are arranged at a 90-degree angle to the direction of travel. Notably, radial tires are the most commonly used types of automobile tires. The two digits that follow, "20," represent the paired tire and wheel diameter inscribed in inches. Thus, the 273/45R20 tire is a 20-inch tire, meant for application on a 20-inch wheel.

### Load Index

The last three numbers -- the ones preceding the letter "V" -- stand for the load index; they comprise a numerical value assigned for the tire's load carrying capability. Therefore, the higher the load index, the greater the load carrying capacity. The 275/45R20 109V, corresponding with a load carrying capacity of 2,271 lbs., or 1,030 kilograms, surpasses the 275/45R20 106V with its load carrying capacity of 2,094 lbs., of 950 kg.

### Speed Rating

The last digit, the letter "V," is the speed rating of the car, measured in kilometers per hour. This consists of the speed capability of tires matched with the peak speed capability of the vehicles they are fitted on. Thus, using the V rating, both the 275/45R20 106V and the 275/45R20 109V tire have a speed capability of 149 km/hr and are applied to sports cars, which typically can go as fast as 240 km/hr.