ISO Sizes for Bicycle Tires and Rims
Think all 26" tires are the same size? They aren't. There are actually three different 26" tire sizes. To get the correct size tire, don't rely on the common size - use the ISO measurement from the tire or measure your rim.
What is the ISO size? It's the diameter of the bead of the rim in millimeters and should match precisely to the rim.
Bicycle Tire Size Markings
Bicycle Rim Sizing
Common Bicycle Tire Sizes and ISO Measurements
Common Name |
ISO in MM |
ISO In Inches |
|
| 12.5" | 203 | 8" | ISO 203 Tires |
| 14" | 254 | 10" | ISO 254 Tires |
| 16" BMX / Kids | 305 | 12" | ISO 305 Tires |
| 16" Recumbent | 349 | 13.75" | ISO 349 Tires |
| 18" BMX / Kids | 355 | 14" | ISO 355 Tires |
| 18" | 400 | 15.75" | ISO 400 Tires |
| 20" BMX / Kids | 406 | 16" | ISO 406 Tires |
| 20 x 1-3/4" | 419 | 16.5" | ISO 419 Tires |
| 20 x 1-3/8", 20 x 1-1/8" | 451 | 17.75" | ISO 451 Tires |
| 22" | 457 | 18" | ISO 457 Tires |
| 22" Wheel Chair | 501 | 19.75" | ISO 501 Tires |
| 24" BMX / Kids | 507 | 20" | ISO 507 Tires |
| 24" Old Schwinn S-7 Size | 521 | 20.5" | ISO 521 Tires |
| 24" Wheel Chair | 540 | 21.25" | ISO 540 Tires |
| 24" Old Schwinn S-5 Size | 547 | 21.5" | ISO 547 Tires |
| 26" Mountain | 559 | 22" | ISO 559 Tires |
| 650c - Small Road Bike | 571 | 22.5" | ISO 571 Tires |
| 27.5 / 650b | 584 | 23" | ISO 584 Tires |
| 26 x 1-3/8 | 590 | 23.25" | ISO 590 Tires |
| 26" Old Schwinn S-6 | 597 | 23.5" | ISO 597 Tires |
| 700c, 29", 28" | 622 | 24.5" | ISO 622 Tires |
| 27" Road | 630 | 24.8" | ISO 630 Tires |
| 36" Big Bike | 787 | 31" |
