There are many sizes for inner tubes, such as wheel circumference, tire width, valve length, and valve type. We will get into each of these factors below.
This article will explain the basics of inner tube measurements and how to choose the suitable one for your tire and wheel.
Determine the wheel diameter
The first step is to find out the wheel diameter. Depending on the type of bike, the wheel diameter can range from 10” to 29”.
| Type of bike | Wheel diameter |
|---|---|
| Kids | 10”, 12”, 14”, 16”, 20”, 24” |
| Mountain | 26”, 27.5”, 29” |
| Road, Cyclocross | 700c (29”) |
| Gravel | 650b (27.5”), 700c (29”) |
Determine the tire width
The second step is to determine the tire width to be used with the inner tube. Depending on the type of bike and tires, the width can vary.
| Type of bike | Tire width |
|---|---|
| Kids | 1.5” to 2.5” |
| Mountain | 1.5” to 2.75” |
| Road, Cyclocross | 21 to 33mm |
| Gravel | 30 to 50mm |
Determine the valve type
The third step is to find out the valve type; Presta or Schrader.
- Presta valves are slimmer and have a locking nut at the tip.
- Schrader valves are thicker and don’t have the locking nut. Schrader valves are also used in automobiles.
| Type of bike | Valve type |
|---|---|
| Kids | Schrader |
| Mountain | Schrader or Presta |
| Road, Cyclocross | Presta |
| Gravel | Presta |
Determine the valve length
Schrader valves are more straightforward and usually have a length of 40mm.
On the other hand, Presta valves can come in various lengths from 30mm to 100mm. The ideal valve length will depend on the rim’s depth (profile).
| Rim profile | Rim depth | Valve length |
|---|---|---|
| Low | Below 30mm | 40mm |
| Mid | 30 to 50mm | 60mm |
| High | Above 50mm | 80mm or more |
How to find the ideal inner tube size
Once you’ve determined the wheel size, tire width, valve type, and length, it’s time to put all these together and shortlist the suitable inner tube.
Inner tube dimensions are denoted by Wheel diameter x Tire width. For example,
- 27.5 x 1.75 – 2.4”, for a mountain bike with 27.5” wheel diameter and suits tire widths from 1.75” to 2.4”.
- 700c x 20 – 28mm, for a road bike with a 700c wheel diameter and suits tires from 20 to 28mm wide.
- 700c x 35 – 44mm, for a gravel bike with a 700c wheel diameter and suits tires from 35 to 44mm wide.
Since the inner tubes can expand and stretch, they tend to suit a range of tire widths. It’s common to find road bike inner tubes in 18 – 28mm, 20 – 28mm, and 28 – 38mm sizes.
Ideally, you want your tire width to fall in the middle of the range.
Once you have nailed down the Wheel Diameter x Tire width, proceed to select the ideal valve length. Most inner tubes have different length variants of the same model.
Choose accordingly.
Alex Lee is the founder and editor-at-large of Mr. Mamil. Coming from a professional engineering background, he breaks down technical cycling nuances into an easy-to-understand and digestible format here.
He has been riding road bikes actively for the past 12 years and started racing competitively in the senior category during the summer recently.