Common Tire Sizes
Generally, bike tire sizes are indicated with two numbers that correspond roughly to the outside diameter of the tire and the width of the tire. These would usually be measured in inches (26", 27", etc.) or millimeters (650, 700, etc.).
While neither are exact measurements, every tire has its size printed or embossed on the outside near the brand name, just like your car's tires.
ROAD TIRE SIZES
A standard road tire is 700c x 23mm, indicating a tire diameter of approximately 700mm and a width of 23mm. When shopping for road tires, you'll look for 700c x your preferred width, 23mm being the slimmest option and going up to 36mm. 650c: size used on some high-performance road and triathlon bikes, especially those designed for smaller riders.
Twenty-Seven inch was a size used on many older road bikes. It's not used by modern manufacturers, but because so many bikes were made for wheels and tires this size, these tires are still readily available
MOUNTAIN TIRE SIZES
Twenty-Six inch is the most commonly used size for modern mountain bikes and is also used on many hybrid or utility bikes.
The 29er another popular size for mountain bike wheels and tires. It;s actually the same bead-seat diameter as 700c tires, but most 29" tires are simply too wide and tall to fit 700c wheels.
27.5" / 650B
Making a comeback in mountain biking is the 650b. Modern mountain bike tires using this size may be labeled 650B or 27.5". It was also used for some older mountain bikes as well as French utility and touring bikes, and never fell completely out of use.
OLDER TIRE SIZES
Tire sizing is additionally complicated by the fact that older bicycles often used some of these same size designations (particularly 26" and 27") for tires that are not compatible with these sizes (i.e., different ISO numbers / bead-seat diameters).
Check out the following for 20+ year old bike tires sizes explained.
MEASURING WITH ISO
While the first number, the diameter of the tire, is most important in identifying size, there's a little more to how tires are measured with a more globally unified approach.
International Organization for Standardization
Your bike's wheels are designed to work with tires with a very specific bead-seat diameter - that is, the diameter of the tire at the bead, which is the ridge at the edge of the tire that hooks into the wheel rim.
This bead-seat diameter is indicated by a very specific ISO (International Organization for Standardization) number that refers to the diameter, in millimeters, of the tire measured bead-to-bead.
The ISO number for a 700c tire is 622. Each ISO number corresponds to a more general number (like 700c or 26") that is used to indicate the tire's size on the packaging, etc.
The ISO number is almost always also indicated on the tire, in parentheses, with the tire's width indicated first, and then the ISO number.
For example, our 700c x 23mm tire would also be labeled with "(23-622)."
TIRE SIZE CHART
With the variety of measurement systems and bicycle tire size options, we have broken down some more common options in a bicycle tire size chart.
Get in touch with us if we can be of any help in figuring out what size tire you need! We carry a great variety of tires in common sizes, and also carry tires in old and hard-to-find sizes. Contact us at 1-800-682-0570 or [email protected].