You’re almost certain to have one in each tire, but what should you look out for when it comes to bicycle inner tubes?
This is seemingly simple bicycle equipment. But there are a lot of things you need to know.
Inner tube sizes:
The first is the diameter of the tube. Most road bikes will be equipped with 700c wheels and require 700c inner tubes.
But there are other sizes in use. Some cities and hybrid bicycles use 26-inch wheels, usually with larger tire widths, and need to use inner tubes of different sizes, while folding bicycles and children’s bicycles usually use wheels of different sizes again.
Next is the tube’s width. Many 700c tubes come to fit tires up to 25mm, which are often fitted to road bikes. But you can also find wider tubes to fit the 28mm tires that are increasingly fitted to road bikes. Many city and hybrid bikes with 700c wheels will have even wider tires and will need a wider tube still.
Bike inner tubes for narrower tires will usually fit these wider tires; they will just be a bit more stretched out to fill the space. They’re unlikely to burst, but if you get a flat they may go down more quickly. On the other hand, a wider inner tube may be awkward to get into a 25mm tire.
Mountain bike tire sizes are usually stated in inches. So a 29 inch MTB tube will have the same diameter as a 700c road wheel, while a 27.5 inch tube will be the same diameter as a 650b road wheel. You can also get 26 inch MTB tubes. But since MTB tires are typically wider than road tires, they may be too wide to fit.
Valve types:
Presta valve inner tube
Most bikes come with wheels that use presta valved tubes. These valves are quite narrow and have a screw at their valve tip. You need to unscrew it to get air into the tire. Although the tire will stay inflated with the screw loose, it’s a good idea to close it up so that you don’t accidentally let air out of your tire. And a valve cap will stop muck getting into it when riding.
Schrader valve inner tube
Some bike inner tubes have Schrader valves like those used on car tires. These won’t fit into a wheel drilled for a presta valve. Likewise, if your wheel has a valve hole the right diameter for a Schrader valve, a presta valve will not fit securely and there’s a risk the tube will get pinched in the valve hole and blow out.
Woods valve inner tube
More of a rarity is the Woods valve. This looks like a presta valve, but has a collar holding the valve core in place. Not all modern pumps will fit onto a Woods valve because of the collar.
Material:
The majority of inner tubes will be made of butyl rubber. It’s the least expensive material and also the most robust. A butyl tube will be black and is repairable with a standard puncture kit if you get a flat.
Another raw material is natural rubber, which is a material used in the traditional technology. Compared with butyl rubber, its air tightness is much worse. Usually, you need to inflate the tires after a week of riding.
Puncture proofing bike inner tubes
If your tube has a removable core, you can get additional puncture protection by adding sealant to it. You take out the core, add around 25 to 30ml of sealant and refit the core. Again, this may not deal with the largest holes, but may help keep you going. But if you do flat, the sealant may stop a patch from adhering to the tube, so it’s a good idea to carry a spare to get you home.
Finally, you can buy bike inner tubes already filled with sealant, for an easy way to get some additional puncture protection.
