IRC GS-23 Grand High Speed Cruiser Tires

Look along the rim of your tire. You should be able to find a group of numbers separated by slashes and/or dashes. There are two general types of tire sizing, metric and english. Most street and dirt bikes use metric sizes. A metric size will look like 100/90-19. Most ATVs use english sizes, english size will look like 35x10-15.