Sometimes buying tires and tubes can be confusing. The confusion arises from there being several different ways to represent tire sizes, tire load ratings and tire speed ratings. I often times use the metric tire size to replace the tires on my KLR, but than use the inch size to buy tubes for the same tire. Knowing how to convert between the two is helpful when buying tires and tubes. You can use the charts below for this, or a factor number and formula for converting between metric and inch tire widths. Here is the number and formula:
MW = Metric Width
IW = Inch Width
IW(25.4) = MW or MW/25.4 = IW
For example, the rear tire on my KLR has a metric size of 130/80-17, but tube manufacturers will often display their tube sizes using inch units. 130 in 130/80-17 is the tire width in millimeters. To convert 130 mm to inches I simply plug 130 into the formula, which gives me: 130/25.4 = 5.11, so the closest tube size of 5.10-17 is a good fitting tube for my 130/80-17 tire size. (The number 17 is the rim diameter in inches. The rim diameter is displayed in inches in both the metric and inch tire size.)
Metric Tire Designation:
Inches Tire Designation:
Alphanumeric Tire Designation:
- Aspect ratio is a percent number, which defines the height of the tire and says the height is a percent of the tire width. For example a 130/80-17 tire size has an aspect ratio of 80. This means the height of the tire is equal to 80%(130mm tire width) = 104mm
- Load Rating is the maximum weight a tire can carry.
- Speed Rating is the maximum speed a tire can go carrying the maximum load.
Street Front Tire Size Conversion Chart| Metric | Alphanumeric | Inch |
| 80/90 | MH | 2.50/2.75 |
| 90/90 | MJ90 | 2.75/3.00 |
| 100/90 | MM90 | 3.25/3.50 |
| 110/90 | MN90 | 3.75/4.00 |
| 120/80 | N/A | 4.25/4.50 |
| 120/90 | MR90 | 4.25/4.50 |
| 130/90 | MT90 | 5.00/5.10 |
Street Rear Tire Size Conversion Chart| Metric | Alphanumeric | Inch |
| 110/90 | MP85 | 4.50/4.75 |
| 120/90 | MR90 | 4.50/4.75 |
| 130/80 | N/A | 5.00/5.10 |
| 130/90 | MT90 | 5.00/5.10 |
| 140/80 | N/A | 5.50/6.00 |
| 140/90 | MU90 | 5.50/6.00 |
| 150/80 | MV85 | 6.00/6.25 |
| 150/90 | MV85 | 6.00/6.25 |
Off Road Front Tire Size Conversion Chart| Metric | Alphanumeric | Inch |
| 60/100 | 90/80 | 2.50/2.75 |
| 70/100 | 90/90 | 2.75/3.00 |
| 80/100 | 100/80 | 3.00/3.25 |
Off Road Rear Tire Size Conversion Chart| Metric | Alphanumeric | Inch |
| 80/100 | 80/90 | 2.50/3.60 |
| 90/100 | 110/90 | 3.60/4.10 |
| 100/100 | 120/80 | 4.00/4.10 |
| 110/100 | 130/80 | 4.00/4.50 |
| 120/100 | 140/80 | 5.00/5.10 |
Tire Speed Ratings (New Style)| Speed Rating | Maximum Speed (MPH) |
| J | 62 |
| K | 68 |
| L | 75 |
| M | 81 |
| P | 93 |
| Q | 99 |
| R | 106 |
| S | 112 |
| T | 118 |
| U | 124 |
| H | 130 |
| V | 149 |
| W | 168 |
| Y | 186 |
Tire Speed Ratings (Old Style)| Speed Rating | Maximum Speed (MPH) |
| J | 62 |
| N | 87 |
| P | 94 |
| S | 112 |
| H | 130 |
| V | 149 |
| Z | 149+ |
Motorcycle Tire Load Index| Load Index | Kilograms | Pounds |
| 43 | 155 | 342 |
| 44 | 160 | 353 |
| 45 | 165 | 364 |
| 46 | 170 | 375 |
| 47 | 175 | 386 |
| 48 | 180 | 397 |
| 49 | 185 | 408 |
| 50 | 190 | 419 |
| 51 | 195 | 430 |
| 52 | 200 | 441 |
| 53 | 206 | 454 |
| 54 | 212 | 467 |
| 55 | 218 | 481 |
| 56 | 224 | 494 |
| 57 | 230 | 507 |
| 58 | 236 | 520 |
| 59 | 243 | 536 |
| 60 | 250 | 531 |
| 61 | 257 | 567 |
| 62 | 265 | 584 |
| 63 | 272 | 600 |
| 64 | 280 | 617 |
| 65 | 290 | 639 |
| 66 | 300 | 661 |
| 67 | 307 | 677 |
| 68 | 315 | 694 |
| 69 | 325 | 716 |
| 70 | 335 | 739 |
| 71 | 345 | 761 |
| 72 | 355 | 783 |
| 73 | 365 | 805 |
| 74 | 375 | 827 |
| 75 | 387 | 853 |
| 76 | 400 | 882 |
| 77 | 412 | 908 |
| 78 | 425 | 937 |
| 79 | 437 | 963 |
| 80 | 450 | 992 |
| 81 | 462 | 1019 |
| 82 | 475 | 1047 |
| 83 | 487 | 1074 |
| 84 | 500 | 1102 |
| 85 | 515 | 1135 |
| 86 | 530 | 1168 |
| 87 | 545 | 1201 |
| 88 | 560 | 1235 |
| 89 | 580 | 1279 |
| 90 | 600 | 1323 |
