Understanding Bicycle Tire Sizes

Sizes written as decimals such as 2 75 are different than sizes expressed as fractions such as 2 3 4.

Understanding bicycle tire sizes.

26 iso size 559 is the most commonly used size for modern mountain bikes and is also used by many hybrid bikes. The letter at the end of a tire size is a throwback to an old french system when the letters a b and c designated different inner tire diameters it does not stand for cm. 700x25c indicates a tire with a 700mm outer diameter and a 25mm width. A third type of tire size might appear on either a mountain or a road tire.

Take the rim with you when buying a tire and vice versa. Finding the right inner tube depends on the size of the tires on your bike. 29 x 2 3 indicates a tire with a 29 outer diameter and a 2 3 width. Read the size carefully.

The table below lists most of the sizes of tyre that are likely to be found in the uk. There are french sizes for variants of the 26 wheel. Between 18 622 and 25 622 there are tyres of 19 20 22 and 23mm section. A tire size you might see on a road bike.

Iso uses two numbers. The first one is the width of the tire or rim in mm. While you can find a variety of bikes with wheel sizes ranging from 16 to 27 5 inches the most common sizes include 26 inches 27 5 inches 29 inches and 700c. Nowadays bike tires are typically marked according to iso standard a system originally developed by etrto european tire and rim technical organization but older english and french tire size dimensions are still used as well use the data from the following tables to determine interchangeability and convert between iso etrto english.

A hybrid of road and mountain tires cyclocross tires are labeled as 700c and have widths indicated in millimeters like road bikes yet are knobbie like mountain bike tires. Sizes of 26 and 24 tubulars are not well standardized. 23c 25c and 28c their width in mm. There are five tire diameter sizes that are in common use on modern standard adult bicycles.

Where you see a block of two or more compatible sizes having the same bead diameter you can assume that intermediate sizes exist that will also fit the same rim. Size variations of tubulars are covered in sutherland s handbook for bicycle mechanics 7th edition available from sutherland s and on the mechanic s bookshelf at better bike shops. With french measurements and mountain bike tires all you really need to know is that 650b 27 5 and 700c 29. The 2nd iso number is found on the diameter of the drop seat of the rim in mm.

When it comes to choosing width there are two major factors at play. Bike tire size meaning. However the most common 26 wheel which is denoted by 26 1 0 or 559mm bsd does not have a designated french size. Conversion tables for common bicycle tire sizes.

A tire size you might see on a mountain bike.