Understanding Bicycle Tire Sizes

Take the rim with you when buying a tire and vice versa.

Understanding bicycle tire sizes.

Sizes of 26 and 24 tubulars are not well standardized. With french measurements and mountain bike tires all you really need to know is that 650b 27 5 and 700c 29. Iso uses two numbers. 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.

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. However the most common 26 wheel which is denoted by 26 1 0 or 559mm bsd does not have a designated french size. The first one is the width of the tire or rim in mm. Road bike tires generally come in three widths.

27 iso size 630 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. There are five tire diameter sizes that are in common use on modern standard adult bicycles. A tire size you might see on a road bike. Sizes written as decimals such as 2 75 are different than sizes expressed as fractions such as 2 3 4.

Finding the right inner tube depends on the size of the tires on your bike. 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. 23c 25c and 28c their width in mm. A third type of tire size might appear on either a mountain or a road tire.

700x25c indicates a tire with a 700mm outer diameter and a 25mm width. 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. Bike tire size meaning. There are french sizes for variants of the 26 wheel.

The international organization for standardization iso has upgraded a universal tire sizing method which removes this complexity. Between 18 622 and 25 622 there are tyres of 19 20 22 and 23mm section. 29 x 2 3 indicates a tire with a 29 outer diameter and a 2 3 width. 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.

26 iso size 559 is the most commonly used size for modern mountain bikes and is also used by many hybrid bikes. The table below lists most of the sizes of tyre that are likely to be found in the uk. Conversion tables for common bicycle tire sizes. When it comes to choosing width there are two major factors at play.

Read the size carefully.