Trying to explain bike inner tube sizes is not that difficult. A typical tube may be described as 26 x 1.95-2.125 inches. What this means is the tube is compatible with 26 inch wheels. The 1.95 to 2.125 figures refers to the diameter range. The 26 inch wheel is the standard, but 27 and 29 inch wheels are available.
Road bikes are more apt to use 700c tires, which are bigger than the standard 26 inch. BMX bikes use smaller 20 inch tires. 700c is 29 inches. Most tubes are built for 700c and 26 inch tires. These measurements refer to the tire diameter after it is installed. Tubes for 28 and 24 inch tires have different specs. However, the stated diameters may not strictly correspond with the tire’s physical diameter.
Some 26 inch tires are 2.125 inches wide. That is the case with older tires. This made them much deeper than modern versions. When trying to explain bike inner tube sizes, it pays to know about tire designations. These are set upon the wheel size used for fitting old wheels. You can find proper tube dimensions depending on the wheel specifications.
Notes on Tube Widths
There are different widths for tubes. The widths in 700c tires are typically 18 mm to 35 mm. Most of the time the figures are in millimeters. But there are now some tires which use inches for measurement. The range in this case is 1 to 3 inches. As a rule, tube dimensions are flexible. For instance, it is possible to utilize a 26 x 1.25 tube on a tire that is 1.5 x 26 inches. But a tube with a different diameter than the bike tire is not compatible.
The general rule followed by bikers is that if the width of the tube is within 3/4 of the tire width, it is compatible. This is applicable for 26 inch tires. Many have used this on comfort bikes, hybrid and mountain bikes without any problems. If you have 27 or 700c tires, you can try tubes that are within 3/8 of an inch.
The easiest way to explain bike inner tube sizes is by checking the figures. You can find it on the bike. If you are looking for a tube, check the tire measurements. You will find it on the outer wall. If it is not there, the info will be on a sticker on the unit.