Tire Size
Most tire sizes are specified with two numbers. The first number refers to the rim size that the tire is designed to fit, and is roughly equal to the outside diameter of a typical tire. The second number refers to the width of the tire. For example, a standard road tire like the Michelin Pro3 Race Tire is specified as 700C x 23, which indicates a tire that is approximately 700mm in diameter and 23mm wide. In actuality, neither of these number is an exact measurement.
In choosing a new tire for your bike, the important specification is the rim size (700C in the above example). A tire of the wrong rim size will not fit on your wheel. The width is less important, as most wheels will be able accept a fairly wide range of tire widths.
There are five tire rim sizes that are in common use on modern standard adult bicycles.
- 26" is the most commonly used size for modern mountain bikes and is also used by many hybrid bikes. This size is very popular and tires like the Kenda Small Block Eight and the Michelin Country Rock Tire can be interchanged depending on season or application. Shop 26" Tires >>>
- 27" is an older size that was used for road bikes, but since so many bikes were built with this size, it is still readily available. The Kenda K35 27 Inch Tire is probably our most popular 27" replacement because of value, and classic look. We also offer 27" tires with modern features like the Schwalbe Marathon 27" Tire for heightened puncture protection, or the Vittoria Rubino Tech 27 Inch for a road race tire type feel. Shop 27" Tires >>>
- A 29" tire like the Panaracer Fire Cross Tire is actually the same rim diameter as 700C, but most 29" tires will not fit 700C road rims because they're too wide. Shop 29" Tires >>>
- 650C tires such as the Continental Grand Prix Triathlon Tire are used for smaller road bikes and triathlon bikes . Shop 650C Tires >>>
- 700C is the most commonly used size for modern road bikes. Shop 700C Tires >>>
In addition to these now common sizes, there are at least a dozen other tire sizes that are used on recumbents, children's bicycles, folding bicycles, and older bicycles. Some of these sizes are very difficult to tell apart. For example, there are six different tire sizes that we're aware of that are all called 26". If you have an older bicycle (more than 15 years old) that is labeled 26", take a look at our article on 26 inch tire sizes. There are also several different 20 inch and 24 inch sizes.
Tire Width
As mentioned above, tire width is less critical when fitting tires to your bike. Most rims can handle almost a 2 to 1 range of tire widths. In other words, the same rim can handle a tire that is 20mm wide and a tire that is 40mm wide. This is an extreme case, but indicates how much leeway you have in tire width size. However, you may not have adequate clearance between your tire and your bicycle frame, fork, or brakes to handle a tire that is considerably wider than the bike and wheels were designed for. Before increasing your tire size, make sure the new tire isn't going to rub against something.
Older Tire Sizes
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 tires sizes. Over the last twenty years, the industry has started to stabilize on the relatively few tire sizes mentioned above. Owners of older bicycles, though, have quite a challenge in finding the right size tire to fit their bicycle.
At BicycleTires, we try to provide the broadest selection possible to fit older bikes, but many of the older tire sizes are no longer available as new. You may therefore need to find someone carrying old stock in order to find some of these more obscure tire sizes. If you have an older bike that you're trying to fit with new tires, perhaps this information will help you find what you're looking for.
Tire widths are specified as either a decimal number (e.g., 1.5") or a fractional measurement (e.g., 1 1/2"). Generally, tires that are specified with decimal widths are not compatible with tires specified in fractional widths, due to slightly different rim sizes.
This table is a pretty complete list of the standard tire sizes used over the years.
ISO (ERTRO) Tire Sizes
In order to reduce some of the confusion surrounding tire sizes, 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 also uses two numbers, although they're reversed from traditional measurements. The first number refers to the tire or rim width in millimeters and the second refers to the diameter of the bead seat of the rim (the rim diameter measured from the area inside the rim where the tire's bead sits), also in millimeters. For example, a 700C x 23 tire would be specified as 23-622. The bead seat diameter of a 700C rim is 622mm.
Many older European manufactured tires and rims (and almost all modern tires) will have this ISO measurement printed on them, it is helpful in determining what size tire you really need.
For more assistance finding the right tire contact us at (800)479-9350 or sales@bicycletires.com.