Not sure how to read your tire size? Find out here!
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How to find your tire size?
Use our guide above to easily and quickly find your tire size from the side of your existing tires. Still need help? Alternatively you can take a picture of your tire and send it to us here.
How to read your tire size?
The first number to appear in your tire size information is the width, in millimeters, of the correct tires for your vehicle: P245/35ZR20 91Y. Tire width always refers to the measurement from one sidewall to another. Thus, a tire with the measurement “P245” is for a passenger vehicle and has a nominal width of 245 millimeters.
Width
The first number to appear in your tire size information is the width, in millimeters, of the correct tires for your vehicle: P245/35ZR20 91Y. Tire width always refers to the measurement from one sidewall to another. Thus, a tire with the measurement “P245” is for a passenger vehicle and has a nominal width of 245 millimeters.
Aspect Ratio
After the slash mark, the next number you see is for the tire’s aspect ratio, which essentially tells you how tall your tire’s profile is: P245/35ZR20 91Y. Aspect ratios are delivered in percentages. Tire makers calculate the aspect ratio by dividing a tire’s sidewall height by its width “P245”. If a tire has an aspect ratio of 35, it means the tire’s height is 35% of its width or “P245”.
Rim Diameter
The next number is the wheel’s diameter. For example, a tire with the P245/35ZR20 91Y would fit a rim with a 20-inch diameter. Take note: if you decide to change your rims’ size, you will also need to get new tires that are compatible with the change in size. Tires designed to fit a 20-inch wheel diameter will not stretch to fit on new 22-inch rims.
Load Index
It is called the load “index” because the figure doesn’t tell us the precise number of pounds the tire can support, at least not by itself. Instead, the number corresponds to a specific load capacity listed in an index. Beginning with one and ending with 150, numbers in the load index represent carrying capacities of 99 to 7385 lbs.
Load Index Chart
| Load Index | Pounds | Kilograms |
| 70 | 739 | 335 |
| 71 | 761 | 345 |
| 72 | 783 | 355 |
| 73 | 805 | 365 |
| 74 | 827 | 375 |
| 75 | 853 | 387 |
| 76 | 882 | 400 |
| 77 | 908 | 412 |
| 78 | 937 | 425 |
| 79 | 963 | 437 |
| 80 | 437 | 450 |
| 81 | 1,019 | 462 |
| 82 | 1,047 | 475 |
| 83 | 1,074 | 487 |
| 84 | 1,102 | 500 |
| 85 | 1,135 | 515 |
| 86 | 1,168 | 530 |
| 87 | 1,201 | 545 |
| 88 | 1,235 | 560 |
| Load Index | Pounds | Kilograms |
| 89 | 1,279 | 580 |
| 90 | 1,323 | 600 |
| 91 | 1,356 | 615 |
| 92 | 1,389 | 630 |
| 93 | 1,433 | 650 |
| 94 | 1,477 | 670 |
| 95 | 1,521 | 690 |
| 96 | 1,565 | 710 |
| 97 | 1,609 | 730 |
| 98 | 1,653 | 750 |
| 99 | 1,709 | 775 |
| 100 | 1,764 | 800 |
| 101 | 1,819 | 825 |
| 102 | 1,874 | 850 |
| 103 | 1,929 | 875 |
| 104 | 1,984 | 900 |
| 105 | 2,039 | 925 |
| 106 | 2,094 | 950 |
| 107 | 2,149 | 975 |
| Load Index | Pounds | Kilograms |
| 108 | 2,205 | 1,000 |
| 109 | 2,271 | 1,030 |
| 110 | 2,337 | 1,060 |
| 111 | 2,403 | 1,090 |
| 112 | 2,469 | 1,120 |
| 113 | 2,535 | 1,150 |
| 114 | 2,601 | 1,180 |
| 115 | 2,679 | 1,215 |
| 116 | 2,756 | 1,250 |
| 117 | 2,833 | 1,285 |
| 118 | 2,910 | 1,320 |
| 119 | 2,998 | 1,360 |
| 120 | 3,086 | 1,400 |
| 121 | 3,197 | 1,450 |
| 122 | 3,307 | 1,500 |
| 123 | 3,417 | 1,550 |
| 124 | 3,527 | 1,600 |
| 125 | 3,638 | 1,650 |
| 126 | 3,748 | 1,700 |
Speed Rating
The final figure in a tire size sequence is the speed rating indicated by a letter: P245/35ZR20 91Y. Just as your load index number corresponds to a particular load, your speed rating letter corresponds to a specific speed capability based on a standardized laboratory test. Here are the most common letters for speed ratings and their corresponding maximum speeds:
Speed Rating Chart
| Speed Rating | Speed (km/h) | Speed (mph) |
| A1 | 5 | 3 |
| A2 | 10 | 6 |
| A3 | 15 | 9 |
| A4 | 20 | 12 |
| A5 | 25 | 16 |
| A6 | 30 | 19 |
| A7 | 35 | 22 |
| A8 | 40 | 25 |
| B | 50 | 31 |
| C | 60 | 37 |
| Speed Rating | Speed (km/h) | Speed (mph) |
| D | 65 | 40 |
| E | 70 | 43 |
| F | 80 | 50 |
| G | 90 | 56 |
| J | 100 | 62 |
| K | 110 | 68 |
| L | 120 | 75 |
| M | 130 | 81 |
| N | 140 | 87 |
| P | 150 | 93 |
| Speed Rating | Speed (km/h) | Speed (mph) |
| Q | 160 | 99 |
| R | 170 | 106 |
| S | 180 | 112 |
| T | 190 | 118 |
| U | 200 | 124 |
| H | 210 | 130 |
| V | 240 | 149 |
| W | 270 | 168 |
| Y | 300 | 186 |
| ZR | Over 2400 | Over 150 |
A quick guide to decoding the information on the tire sidewall
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