Proper inner tube sizing of your replacement tube is critical, not just on your mountain bike but for any kind of bike. However, the difference in sizes and even measuring units can confuse things. So, I thought it best to create this handy guide – all about sizing inner tubes for mountain bikes (and other bikes – while we’re at it).

Inner tubes come in various diameters, widths, and even thicknesses, and materials may differ from one to another. Properly sizing your inner tubes to match the requirements of your tire (sizing embossed on the sidewall) or your rim is essential for a safe riding experience.

In this article, I will explain exactly how to size your MTB inner tube replacements. I’ve even got a few handy tricks to help you. So, stick around because I’m pumped about sharing my inner tube secrets with you. Learning new things that make tube replacements easier is always good, so let’s get started.

Different size bike tubes
Different size bike tubes

How Do I Know What Inner Tube to Buy for My Bike?

An inner tube is a toroid-shaped balloon with a valve. That’s it, it’s not a huge deal, but if you buy the wrong one for your bike, you may not be able to use it and wind up having to return it to buy the right one. Furthermore, if you take it to a bike shop, you must haul your bike, wait up to a week (sometimes two, depending on the shop’s popularity), and you’ll be out at least $50 in most cases.

Replace your inner tube and save a small fortune. Yeah, I like that idea too. So, how do you choose which inner tube to buy for your bike? Let’s start by talking about what the differences are between the types. After all, you don’t start anything halfway through; you start at the beginning.

Here’s My Shortcut Chart for Getting an MTB Tube

If you pick a tube that is mid-sized it will cover 90% of all uses. Here are some quick sizes and compatible tubes.

29 inch Tires

29 inch Tire Recommended TubeShortcut Link to AmazonπŸ‘‡
1.75 to 2.5 inch tube widthContinental MTB 29Conti Tube MTB 29

27.5 inch Tires

27.5 inch Tire/WheelRecommended TubeShortcut Link to Amazon πŸ‘‡
1.75 to 2.5 inch tube widthContinental MTB 27.5Conti Tube MTB 27.5

26 Inch Tires

26 inch Tire/Wheel SizeRecommended TubeShortcut Link to Amazon πŸ‘‡
1.75 to 2.5 inch tube widthContinental MTB 26Conti Tube MTB 26

How to Determine the Right Inner Tube Size for Your MTB

Start With the Right Size

It may seem obvious, but you’d be surprised how many people get this wrong. Here’s how to know what size of inner tube you need:

1. Clean your tires.

Bike tire and valve in the mud
Bike tire and valve in the mud

They don’t have to be clean enough to eat off of, but you should ensure they are clean enough not to drop dirt or other debris into the rim.

2. Inspect the sidewall of the tires.

MTB Tire Side Wall
MTB Tire Side Wall – credit Jeremy Shantz

All mountain bike tires have the size labeled on the sidewall of the tire. Here’s a tire sidewall measurement example: (see the above photo). In my example, the sidewall shows the size of 29 x 2.35. So, it’s a 29″ tire (diameter) and 2.35 inches wide. Now, my rim happens to be tubeless-ready, and my valves are Presta. It doesn’t say Presta on the rim. Still, we’re talking about reading tire sidewall measurements, and you would visually inspect the valve to see the type anyway.

DIYMTB Pro Tip: Need more details for measuring your tire, no worries check out πŸ‘‰ How to Measure a MTB Tire with Examples

3. Nothing on the Sidewall?

If your tire is so worn or old that it no longer shows the size, it’s time to get your measuring tape out (and proceed to the following instructions). If you can read your tire’s measurements, you’re all set. Otherwise, continue to the next set of instructions.

It seems like I’m either: buying, replacing or airing up bike tubes

πŸš΄β€β™€οΈ Can I put a tube in a tubeless tire? I explain with video πŸ‘‰ Can I Put a Tube in a Tubeless Bike Tire?

πŸš΄β€β™€οΈ Presta vs Schrader which tube is better. Find out πŸ‘‰ Presta vs Schrader Valves (Is One Better)

πŸš΄β€β™€οΈ I kept getting flats, are some inner tube brands better? Check out what I think πŸ‘‰ Does the Brand of Inner Tube Matter?

πŸš΄β€β™€οΈ Are you getting a bunch of flats? Read πŸ‘‰ Don’t Get Caught with a Flat: Why Rim Tape is a MUST

πŸš΄β€β™€οΈ Is there a right way? πŸ‘‰ How to Let Air Out of a Bike Tire

πŸš΄β€β™€οΈ Presta Valves it’s a mystery πŸ‘‰ How to Inflate an MTB Tire with a Presta Valve

How To Measure a Rim (With No Tire)

As described above, if you’ve got a half-decent tire, you should be able to read the sidewall measurements. However, in the weird off-chance, you acquire a bike or rim with no tire, it’s pretty easy to measure.

First, check the rim

Look at the markings on the wheel or rim for the size
Look at the markings on the wheel or rim for the size

Often you’ll see the diameter printed on the wheel. Sometimes you might find something like:

559 which the ISO number for a 26 inch wheel

584 = 27.5 inch

622 = 29 inch

Measuring the MTB rim
Measuring the MTB rim

Measure the Rim (Wheel)

Measure from one edge of the rim in a straight line through the center hub/axle to the opposite side of the rim. There aren’t many variations, so you should find it easy to get a number.

Most kids’ mountain bikes in North America start with the smaller 24″ diameter rim, and most big-box stores sell adult bikes with the standard 26″. However, as you noticed in my photo above, the higher-end bikes can come in different sizes, like 29″ (like mine).

So, to sum up, you’ll find one of the following diameters:

24”, 26”, 27.5”, 29”

Next, We Need a Width:

All you need to do to get a width is measure the inside width from one bead of the rim to the other. Width is where you’ll find a lot more variation in sizing. For example, my tire is a 2.35, as you saw in the picture.

However, mountain bike tires can be a lot smaller, for example, 1.9″. They can also be much larger, like a fat tire bike coming in at 3.7 or even as high as 5.2 inches wide.

Here’s a chart that shows everything you need to know for rim/tire/tube width.

Tire & Tube Size (Width)Typical* Internal Rim Width (Bead to Bead)
1.9”0.75” (19mm)
2.0”0.75” (19mm)
2.1”1” (25 mm)
2.2”1” (25 mm)
2.35”1” (25 mm)
2.41” (25 mm)
2.51.25” (32 mm)
2.61.25” (32 mm)
2.71.25” (32 mm)
2.81.25” (32 mm)
3.01.25” (32 mm)
β€˜Fat’ Bike Tires: 
3.71.57” (40mm)
4.01.57” (40mm)
4.52.5” (65mm)
4.62.5” (65mm)

* Typical values are only typical and not set in stone. You will find variations in the market, so don’t get too concerned if your tires or tubes don’t match my table exactly. In other words, take my chart as an example, not the rule.

Standard MTB Inner Tube Sizes and Compatibility

There are all kinds of information on tires out there. Still, thanks to Park Tool, I could compile the following table that goes through all the ISO bead seat diameters, for example, a cross-section of rim types. Some are for BMX and even wheelchairs, but you get a good sense of the different potential sizes on the market.

Tire Size LabelISO Bead Seat Diameter (mm)
16” x 1” to 2.2”305
20” x 1” to 2.2”406
20” x 1-½” or 1-¾”419
20” x 1-⅛” and wider451
24β€³ x 1.0β€³ to 2.0β€³507
24β€³ x 1-3/8β€³540
24β€³ x 1-3/8β€³547
26β€³ x 1.0 to 4.8β€³559
26β€³ x 1 1/2β€³. Also called 650C571
27.5β€³ or 650B584
26β€³ x 1-3/8β€³590
26β€³ x 1-3/8β€³597
27β€³ x 1-1/4β€³630

If you want to look at compatibility for common mountain bike inner tubes, these are the most common:

  • 24” x 1.75-2.125” πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 24″ TUBE
  • 26” x 1.376” πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 26″ TUBE
  • 26” x 1.75-2.125” πŸ‘‰ Shortcut link to Amazon πŸ‘‰26″ TUBE
  • 27.5” x 1.75-2.5” πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 27.5″ TUBE
  • 29” x 1.75-2.5” πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 29″ TUBE
  • 700 x 19-25mm πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 700 1925 TUBE
  • 700 x 28-35mm πŸ‘‰ Shortcut link to Amazon πŸ‘‰ 700 2835 TUBE

As you can see, these standard inner tube sizes are compatible with multiple sizes of tires and rims. That’s the good thing about rubber inner tubes – because they expand under pressure, you can use them for a few different tire sizes, well, widths anyway.

Tubes in a Tubeless Tire?

I get asked about this all the time, but don’t sweat it. Yes you can put a tube in a tubeless tire.

Factors to Consider When Selecting MTB Inner Tubes

Mountain bike inner tubes come in a few varieties. Still, the most noticeable differences (aside from the size) are the valve type and the material used to make the tube. Not to worry, I’m about to explain the differences so you won’t waste a trip to the bike shop.

Schrader, Presta and Woods Valve for Bikes
Schrader, Presta and Woods Valve for Bikes

Different Inner Tube Valve Types

It’s essential to check the valve type before purchasing a new inner tube. Although the valves look similar at first glance, some reasonably distinct differences exist.

Presta Valves

Presta valves are the high-end valves of the market. For the most part, you aren’t likely going to find Presta valves on bikes sold in big box department stores. Of course, times change, but most of the time, you’ll only find Schrader valves on bikes in the big box stores.

Regarding inner tubes, in North America, you’re likely to find only Schrader and Presta valve inner tubes; Schrader being the dominant one, but more on Schrader in a minute.

When the illustrious Presta valve started, it wasn’t called Presta. In fact, the valve’s initial name was the Sclaverand valve, after its creator, a Frenchman named Etienne Sclaverand. For obvious reasons, it is also called the French valve, again due to the origins of its creator.

Presta valves are narrow, coming in at just shy of a quarter inch. For this reason, the rims intended to use Presta valves have a narrow hole requirement. So, if not universal, a rim set up for Presta will not fit the wider Schrader valve. Suppose you see a bushing in the hole. In that case, it’s likely a universal rim, and you could remove the bushing to accommodate the following Schrader valve.

Schrader Valves

Schrader valves are the most common, and thus, so are the Schrader valve inner tubes (as well as rims and bikes set up for those, as mentioned earlier). You’ll find these valves on cars, motorcycles, inflatable wheelbarrow tires, and most inflatable bike tubes found in cycles and for sale in department stores. If you want Presta, you must go to a specialty shop.

Speaking of specialty, you do not need to be concerned about the pump type if you have Schrader. That’s because their popularity means that those air pumps at gas stations, and most bike pumps for sale, for that matter, are set up for Schrader. Other types need a special adapter to work with our common Schrader.

As I described above, the Schrader valve is wider than the Presta, coming in at a sliver over 0.3 of an inch. So, as you can see, a rim with a ΒΌ” hole for a Presta valve won’t accommodate a Schrader. However, the reverse is not necessarily true because you can buy plenty of aftermarket bushings to adapt a Schrader-intended rim to accept Presta valves. Here’s a link to the bushings on Amazon.

Dunlop/Woods Valves

In North America, you don’t see many Dunlop valves. However, if you are in Europe or Asia, they are pretty standard. These valves go by a few different names too. They are called Dunlop valves, Woods valves, English valves, and Blitz valves; although Woods was the first, after the inventor, C.H. Woods.

Countries like Japan, Korea, and most of Europe use the Woods Valve, to name a few. But in the US, they are pretty rare; most people have never heard of them.

Dunlop valves have the same external diameter and thread as Schrader valves (0.305 inches or 7.747 mm x 32 threads per inch). So, you could use them on a Schrader rim, as long as the stem is long enough for the depth of the rim. However, having an adapter to pump them with a standard air pump or at the gas station (in North America) would be best.

Different Materials Used For Tubes

Suppose you were paying attention to my ramblings about inner tube size compatibility. In that case, you’ll know that our friend, rubber, expands under pressure. However, not all inner tubes are made of the same materials.

Butyl Rubber Compounds

Standard inner tubes use butyl rubber, which is a synthetic (human-manufactured) compound. It’s pretty cheap to make, has excellent elastic properties, and is airtight. That is to say, it’s airtight while it’s in good condition and not punctured.

Aside from the fact that it’s cheap and relatively robust, what’s excellent about butyl rubber is that it’s also pretty easy to repair. Typical bike patch kits are available at most stores that also sell bikes. The ease of gluing a patch while on the trail makes butyl rubber tubes a good choice. However, they are a bit heavier than some other types.

DIY Pro Tip: Wondering about the best bike tube to avoid flats? Read πŸ‘‰ The Best Bike Tubes for Avoiding Flats!

Latex Rubber Compounds

You won’t find too many MTB inner tubes in latex, but you will find them in the road bike community. The upside to latex inner tubes is that they are considerably lighter than butyl rubber tubes. However, in my opinion, the downsides outweigh the weight difference.

Latex are:

  • Easy to puncture
  • Loses air quickly (you must re-inflate each ride)
  • Nearly impossible to patch the trail

Common Mistakes to Avoid When Sizing MTB Inner Tubes

Tubeless Ready Bike Tire
Tubeless Ready Bike Tire

Out of all the mistakes I’ve witnessed over the years, the biggest is selecting an inappropriate inner tube size for your tires. People think one of two things: That bigger is better, or that because rubber expands, it can go smaller for a lighter weight.

Both scenarios are wrong. Here’s why:

Bigger Isn’t Better

I’ve seen mountain bikers buy ‘the next size up’ to ensure a robust tube. This poor decision usually follows a flat or two and the frustration of repeated flats. However, getting bigger doesn’t make your tube any less able to get a flat; in fact, it is quite the opposite.

Here’s what happens. Imagine you have a box and a balloon. You cut two holes in the box, one at either end. Let’s say; for argument’s sake, the holes are each 3″ across. Now, if you inflate the balloon inside the box, the balloon would inflate to fill the box, right? Well, what do you think happens next? The balloon starts to squish out of the holes.

Before you know it – POP! The balloon breaks.

Now, think of your tire as the box and the inner tube as the balloon. If you have an inner tube bigger than the tire, it can find its way to squish between tire and rim, and before you know it, one bump on the trail and POP! There goes your inner tube from what we call a pinch-flat. A pinch flat occurs when the tube gets in between the tire and the rim and gets pinched to the point of rupture. So, keep your inner tube size to that noted on your tire sidewall – don’t go bigger; it isn’t better.

Small Tubes Stretch (And Explode)

If you are concerned about weight, don’t try to use a smaller inner tube. A smaller tube might stretch, but let’s return to our balloon and box analogy for a minute. What happens if the balloon is much smaller than the box? It might just pop before even filling the box, right?

An undersized inner tube might fill your tire, but you’ll likely get a flat and fast from the first or second bump on the trail. So, what are your options? Let’s take a look.

Upgrading Your MTB Inner Tubes: Options and Benefits

There are a few ways you can upgrade your inner tube situation. One is to get heavy-duty tubes. Or, you could use a sealant intended to inject into the tube via the air valve. Lastly, you could switch to tubeless tires and forget about inner tubes. Here’s a quick run-down of each option:

For Durability

You can pick up some thick-walled tubes, and some even come with sealant. A common brand you’ll see is the Slime brand. They have both regular tubes with sealant and extra-thick, heavy-duty tubes. I recommend these for kids’ bikes, but I won’t use them on my serious ride, which is tubeless. To each their own.

For Extra Caution

You can use standard inner tubes and a special sealant if you don’t want to trade off the weight for thicker inner tubes. When you use a sealant, it adds weight, but not as much as a thicker inner tube, especially not as much as a thicker tube that also has sealant, that’s for sure.

For Weight Saving

If you want to go all the way and save a ton of weight, you can switch your rims and tires to tubeless. Tubeless is excellent, but they have a catch – lacking inner tubes means you lose a layer of protection in avoiding flats. It’s easier to get a flat on tubeless, but the weight difference makes it preferable for most riders (myself included).

MTB Tools I Love and Recommend

Bike Hand Repair Stand
Bike Hand Repair Stand
Bike Hand 37 pcs Tool Box
Bike Hand 37 pcs Tool Box
Topeak Smartgauge D2 Air Pressure
Topeak Smartgauge D2 Air Pressure

I own each of these tools and only recommend things I own and use.

  • Bike Hand Bike Repair Stand.Β  Nice mountain bikes don’t have a kick stand so keeping your MTB safe but conveniently stored is essential.Β  I keep my bike on my stand whenever I’m not riding it.Β  This makes it easy to lube the chain, inflate the tires and adjust the derailleur.Β  Highly recommended – Bike Hand Bike Repair Stand (πŸ‘ˆ Link to Amazon to see what thousands of others have said)
  • A basic MTB toolbox for replacing a chain, adjusting brakes and dialing in the fit.Β  Bike Hand has a 37-piece box that has most of the specialty bike tools to keep your MTB properly maintained.Β  The Bike Hand brand is value packed for the avid rider.Β  Check out the competitive prices with this link to Amazon πŸ‘‰ Bike Hand 37 pcs Bike Repair Tool Kit
  • Get a good air pressure gauge, if you get just a tiny bit serious about MTBing you’re going to start playing with tire pressure.Β  A couple psi can make your tires sticking or not.Β  Get a good gauge, I highly recommend the Topeak Smartgauge D2, it’s accurate, flexible and easy to use.Β  An Amazon best seller, here’s a link πŸ‘‰ Topeak Smartgauge D2
  • Carry a multitool with you on every ride.Β  I’m serious, most of the time you can MacGyver something to get back to the trailhead if you have a multitool.Β  I’ve got the Crank Brothers M19, it’s worn, rubbed and abused – but it still works.Β Β  Thousands sold on Amazon – check it out with this link πŸ‘‰ Crank Brothers M19

David Humphries is the creator of DIY Mountain Bike. For me a relaxing day involves riding my mountain bike to decompress after a long day. When not on my bike I can be found wrenching on it or making YouTube videos at πŸ‘‰ DIY Mountain Bike Read more about David HERE.

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