Buying new inner tubes shouldn't be intimidating. However, being faced with 50 different styles of rubber tubes, that all look the same, can actually be somewhat confusing. And quite often, you really don't want to have to ask.
The good news is that when you know what you're looking for, it's easy. Firstly, you need to select the tube size that fits your tyre. The tyre size will be written on the sidewall, for example, 700 x 23 (a road bike), 27.5 x 2.4 (mountain bike) or 700 x 35 (a cyclocross of hybrid bike). Most tubes fit a range of tyres, for example, a 700 x 18-23/25 tube will fit road tyres between 18 and 25mm.
Then - you need to choose the right valve. There are two types - Presta, vs Schrader. In most cases, the wheel rim of your bike will only fit one or the other so you need to choose the right one. Thankfully, they look very different- so simply replace like for like and you can't go wrong.
Presta valves require a smaller hole in the wheel rim, can hold higher pressures, and arguably are less susceptible to picking up dirt. To inflate this tube, you simply unscrew the nut on the top and attach the pump - to let out air, you unscrew the nut, and press it down.
Presta valves also come in various lengths - this is so people using deep rim wheels will have enough valve poking out the end to be able to inflate the tube.
Schrader valves are the same as those found on most cars - they're much wider, and won't fit through a hole made for a Presta valve.
These are known to be robust, and long-lasting - and the plus side is if you get stuck with a flat on a ride (and no pump), you can probably sneak some air from your local service station.
Most track pumps have two attachments, so you can pump a Presta or Schrader inner tube, but do check that the two are compatible if you're buying a new pump or new style of tube.
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