Older Tire Sizes
This information is provided primarily for reference. We try to carry a broad selection of tires to fit many different bikes, new and old, but some older tire sizes are no longer available as new. If your bike uses one of these sizes, you may need to find someone carrying old stock. If you have an older bike that you're trying to fit with new tires, this information may help you find what you're looking for.
Bicycles have been around for over a century, so you can imagine the number of different tire sizes that have been produced. For many decades, each country that produced bicycles created their own tire sizes. Over the last twenty years, the industry has begun to standardize the relatively few tire sizes mentioned in our Common Tire Sizes article. Riders of bicycles that are older than that, though, may have quite a challenge finding the right size tire to fit their steed.
Tire widths on older bikes are usually specified in inches as either a decimal (e.g., 1.5") or a fraction (e.g., 1 1/2"). Generally, tires with sizes indicated in decimals are not compatible with tires with sizes indicated with fractions. This can be a clue when you're trying to figure out what size you need.
ISO / ETRTO Sizes
In order to try and reduce some of the confusion, the International Organization for Standardization (ISO) developed a universal tire sizing system, known as the ETRTO system (after the European Tyre and Rim Technical Organization). This tire sizing system specifies a precise measurement of the bead-seat diameter of the tire, so if you know this number (which, if you're lucky, will be printed on your tires or rims), you'll know what size you need for replacement tires.
ISO sizes are indicated with two numbers. The first number is the width of the tire in millimeters; this number is not necessarily a precise measurement, since the internal width of your rim affects how wide the tire will be once it is mounted and inflated. The second number is the one that's important in this context—it's the bead-seat diameter of the tire, also in millimeters. For example, a 700c x 23mm tire's ISO size indication would be 23-622. The bead-seat diameter of a 700c tire is 622mm.
Our Tire Size Chart includes many of the standard ISO tire sizes used in the past few decades. We sell tires to fit most, but not all, of these sizes.
Please note that just because two tires have the same bead-seat diameter or ISO indication does not necessarily mean they are compatible. For example, older bicycle tires used a straight-sided rim. As tire pressures increased, bike tires started to use a hooked rim so that the tire bead would be held more firmly. Additionally, a tire may be too wide or narrow for a rim, despite having the correct ISO number. For example, 700c and 29" tires both have an ISO number of 622, but 29" tires tend to be much wider than 700c tires.
We hope this information will be helpful to you. If we can help in any way, please contact us at 1-800-682-0570 or [email protected].