Understanding Bicycle Tire Sizes

700x25c indicates a tire with a 700mm outer diameter and a 25mm width.

Understanding bicycle tire sizes.

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. A tire size you might see on a road bike. A tire size you might see on a mountain bike. 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.

A third type of tire size might appear on either a mountain or a road tire. Between 18 622 and 25 622 there are tyres of 19 20 22 and 23mm section. With french measurements and mountain bike tires all you really need to know is that 650b 27 5 and 700c 29. The table below lists most of the sizes of tyre that are likely to be found in the uk.

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. Sizes of 26 and 24 tubulars are not well standardized. 26 iso size 559 is the most commonly used size for modern mountain bikes and is also used by many hybrid bikes. There are five tire diameter sizes that are in common use on modern standard adult bicycles.

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. The 2nd iso number is found on the diameter of the drop seat of the rim in mm. 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. However the most common 26 wheel which is denoted by 26 1 0 or 559mm bsd does not have a designated french size.

Read the size carefully. Iso uses two numbers. Bike tire size meaning. Road bike tires generally come in three widths.

There are french sizes for variants of the 26 wheel. When it comes to choosing width there are two major factors at play. 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. The first one is the width of the tire or rim in mm. 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. 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.

Conversion tables for common bicycle tire sizes.