How do I pick the right replacement tube for my bike?

Q: How do I pick the right replacement tube for my bike?

A: There are dozens of different tube sizes for bicycles, and picking the right one can be confusing when you go into a store. But there are really only three main facts you need to know, and after that the choice gets much easier.

Two type of valves

The first thing to know is that there are two types of valves on almost all modern bikes. One type is called the Schraeder valve (often abbreviated “SV”). This type is sometimes called the American valve (abbreviated “AV”). This is the kind of valve used on car tires: it looks like a short straw with black rubber sides. Inside the valve is a little spring loaded metal pin, that lets out air when you press down on it.

The second type of valve is called the Presta valve (abbreviated “PV”), or sometimes called the French valve (“FV”). This valve is skinnier than the Schraeder valve. The Presta valve is all metal, and its sides are threaded. The Presta valve also has a little metal pin that holds the air in, but it is not spring loaded. Instead there is a small nut that you spin down to hold the valve shut. You have to spin this nut loose to open the Presta valve when you want to put air in the tube.

So, first fact: if your bicycle wheels have valves that look like car tire valves, you need Schraeder valve tubes. If your bike has skinnier, all metal valves, you need tubes with Presta valves.

(Some bikes with Presta valves have “deep section” rims that only work with longer than normal Presta valves. This used to be rare but is becoming more common. Replacement tubes with longer Presta valves will be marked as such. The common lengths are 44mm and 60mm. There is no harm in using a tube with a longer than necessary valve, so if in doubt buy the right size tube with a long valve.)

Tire size

There are lots of different wheel sizes on bikes today (20”, 24”, 26”, 700c, etc.), and lot of different tire widths for all those different wheel sizes. Fortunately, tires are marked with their size, so you just need to learn how to read those markings, and they are not complicated.

For the purpose of picking a replacement tube, there are just two numbers you need to know: tire diameter and tire width. These numbers are always written somewhere on the side of each tire. (Sometimes when tires get old the numbers are hard to see. Don’t give up, just keep looking.) Here are some examples of what the numbers might say: 26×1.95, 700c x 25. Sometimes the there will be three numbers, something like this: 26×1-1/2×1-3/4. Don’t worry about that, just remember the first number (26 in this example), and the larger of the other numbers (1-3/4 in this case). Sometimes there will be letters with the size (such as EA3 or S-6). Sometimes there will be another number or two in parentheses, for example (622) or (559-45). Don’t worry about those letters and numbers. They are important for getting a replacement tire that fits, but not important for replacing the tube.

The numbers can be hard to remember. It’s a good strategy to write them down somewhere to bring with you.

Tubes stretch

Tubes are flexible. One tube size fits in several tire sizes, and the tube’s box will be marked to indicate that fact. You need to find a tube that is the right diameter (26”, 24”, 700c, whatever). Then, check that the tire width you have (25c, 1.95”, whatever) is somewhere in the range of widths that that tube is designed to fit. If not, look for a different tube that will handle that width and diameter. Remember, look for your tire’s width to be somewhere in the range the tube fits. It doesn’t have to (and often won’t) match exactly.

Sometimes you can’t find a tube that matches your tire’s width. That isn’t necessarily the end of the world. It is usually OK to use a tube that is a little too narrow or a little too wide. If the tube is slightly too narrow, it will stretch to fit once you get everything back together and inflated. It will stretch more than normal and will be slightly more prone to getting flats. But if you normally don’t get flat tires often, you might never notice. If the tube is slightly too wide, it will be more difficult to install when you are remounting the tire (and a bit heavier than necessary), but once back together you’ll have no problems. (A tube that is a lot too wide sometimes stays folded up even when inflated in the tire. That can lead to flats also, so is not a good solution except in emergencies.)

Review

There are three keys to getting the right replacement tube. First is to identify the valve type, and remember to check the box of the replacement tube to make a match. The choices are Schraeder (SV, like a car tire valve) and Presta (PV, skinny metal valve). Second, find the tire size written on the tire sidewall, write it down, and bring that information with you to buy the tube. Find the closest match you can among the tubes available to purchase. Third, don’t worry that the tube size doesn’t exactly match your tire’s size. Tubes stretch, and within limits one tube fits many different size tires.