Which inner tube to order: size from the tire, valve from the rim

Three things decide the tube you order: the ISO size on your tire, the valve hole in your rim, and how deep the rim is at that hole. This page shows how to read each one and what to check on a tube's listing before you buy.

The short answer

Order by the numbers, not the wheel's nickname. Find the ISO size on your tire's sidewall, such as 35-622: width in millimeters first, bead seat diameter second. Buy a tube whose listed range includes that bead seat and your width. Match the valve to the rim hole: Presta (also sold as Sclaverand or SV) for the narrow hole, Schrader (AV) or Dunlop (DV) for the wide one. Then pick a valve long enough to pass through the rim with room left for your pump head. The tube makers quoted below give no formula for that, so measure, or copy a tube that already works.

Example: a 35-622 tire, sold as 700 x 35C, falls inside the range Schwalbe lists for its standard No. 17 tube (28→47-622) and the one Continental lists for its Tour 28 All (32-622->47-622/42-635). It falls outside Schwalbe's No. 15 (23→30-622).

Step 1: read the tire, not the wheel

Schwalbe describes an ETRTO size such as 37-622 as width (37mm) and inner diameter (622mm), and calls it unambiguous. Inch names are not: Schwalbe notes that 559, 571 and 590mm tires are all called 26-inch, and 622 and 635mm tires are both called 28-inch. In 700 x 35C, the C stands for 622mm. For 20-inch tires, Sheldon Brown's size table puts 20 x 1.5 to 2.125 on 406, but 20 x 1 1/8 to 1 3/8 and OS20 sizes such as OS20 x 1.75 on 451.

Names mislead even when the diameter looks right. Sheldon Brown calls fraction-versus-decimal widths the most common cause of mismatches: two sizes that are equal in math, one written as a fraction and one as a decimal, are generally different tires. His table puts 26 x 1 1/2 on 584 but 26 x 1.00 through 5.0 on 559, and Schwalbe's size list gives 26 x 1.50 as 40-559. So a 26 x 1.50 tire takes a 559 tube, not a 584 tube picked for the name 26 x 1 1/2. His table also lists 20 x 1 3/8 NL, a Dutch juvenile size, on 438 rather than 451; Schwalbe's No. 7S lists 37-438 next to its 451 range. Tube boxes share the problem: the inner tube article on Sheldon Brown's site notes two tube sizes both called 24 x 1 1/8, for 520mm and 540mm rims. Order by the ISO number, not the name.

Step 2: check the range for your bead seat

Tubes stretch, so one tube covers many tire sizes. Check that your bead seat is listed and that your width falls inside the range given for that bead seat. Schwalbe's product descriptions spell out each size a tube covers. Continental's chart gives only a first and a last size, and some of its ranges run across two bead seats, such as Compact 20 at 32-406->47-451. If your exact size isn't printed, ask Continental before ordering. Schwalbe's tube finder and Continental's chart are both linked below. Five things to watch:

• The headline label can be wider than the detail. Schwalbe labels No. 19 as 40/62-584/635, but its range on 584 is 50→62. A 45-584 tire is outside it; Schwalbe's No. 14 (40→62-584) lists that size.
• A tube number is not a range. Schwalbe's butyl No. 17 lists 28→47-622 and its Aerothan No. 17AE lists 33→47-622, so a 30-622 tire is on the first list and not the second. Schwalbe has also renumbered tubes: No. 21 became No. 14, and No. 20 became 15-EL.
• Spanning two bead seats is the maker's call. Schwalbe's No. 17 also lists 32-630, 40-609 and 40-635, while its standard 20-inch tubes for 406 (No. 6, No. 7) and 451 (No. 7S, No. 7XS) are separate. Continental's chart gives its Compact 20 as 32-406->47-451. Tires are stricter: a tire whose bead seat doesn't match the rim won't fit. See Will that tire fit that rim?
• Rim width can matter. Schwalbe limits its older Item 20 Extralight tubes (18/25-622/630) to rims up to 19C (19mm inner width), because wider rims enlarge the tire's cross-section and can overstretch the tube.
• Inch ranges are approximate. Some listings give widths in inches, such as 29 x 2.1-2.4. Schwalbe's size list pairs 29 x 2.10 with 54-622 and 29 x 2.40 with 62-622, so that listing spans roughly 54 to 62mm. The pairings are loose: the same list puts 26 x 1.75 against both 44-559 and 47-559, and 700 x 35C against both 35-622 and 37-622. If your width is within a millimeter or two of either end, look for the maker's figures in millimeters.

Why a near miss causes trouble

The inner tube article on Sheldon Brown's site explains the limits. A tube with too large a diameter folds over inside the tire, gives a bumpy ride and can be damaged. One too small stretches over the rim like a rubber band and makes the tire hard to fit. A tube too fat for the tire can stick out under it and stop it seating, or crumple inside. One too skinny stretches too far and may tear or split, which the article warns against especially on a front wheel. Its test: inflate the tube just enough to hold its shape and lay it in the tire. It should leave a gap about as wide as the inside of the rim.

Step 3: match the valve to the rim hole

Schwalbe gives the Presta stem as 6mm against 8mm for the other valves, and says it needs a smaller rim hole. Michelin notes a Schrader is the same size as a car tire valve, and says the valve type must match the rim's valve hole. A Dunlop (Woods) valve has a Schrader-like base, narrows to about Presta size, and can be pumped with a Presta pump. To read your rim, take the tire and rim tape off and measure the hole with calipers, on the side where the tube sits and on the spoke side:

• Under 8mm on both sides: order Presta. Schwalbe gives the other valves as 8mm, so they won't pass. Schwalbe calls 6.5mm the correct Presta hole; the Sheldon Brown tube article gives 7mm.
• About 8.5 to 9mm on both sides, the tube article's figure for Schrader: an 8mm Schrader or Dunlop stem passes. A Presta tube goes in too, but Schwalbe warns that a Presta stem in a larger hole often tears off on the hole's sharp edge. If you use Presta there, the article advises a rubber grommet, and notes that some Presta jam nuts have a flange that fits a Schrader hole and serves as an adapter.
• Narrow on one side and wide on the other, or a reading between these figures: ask the rim or wheel maker which valve the rim is drilled for. Schwalbe notes rims that are 6.5mm on the outside and 8.5mm on the inside, and says that step causes the same tear-off.
• Check the pump. Presta and Schrader need different pump fittings, and Continental's tube FAQ suggests checking that your pump matches the valve.
• Schwalbe's Clik Valve (SCV) is listed first in its tube finder. Schwalbe's product pages list an SCV version for some tube numbers, such as No. 17, and none for No. 12S, 7S or 7XS, so check the valve options on the tube's own page. Schwalbe's Clik Valve page doesn't give an SCV tube's stem diameter or the rim hole it needs; ask Schwalbe before ordering one. It clicks into Schwalbe's own pump head or adapter. A clamp-on or push-on Presta head also inflates it, a screw-on head won't, and a normal Presta pump can't read its pressure.

Step 4: valve length, measured

Continental puts it plainly: the valve must pass through the rim and still leave enough showing to attach a pump, and deeper rims need longer valves. Michelin says to confirm, on deep-section rims, that the stem clears the rim height. The Sheldon Brown tube article adds that a stem only just long enough is less likely to be bent or broken. None of them gives a formula, so work it out on your own wheel:

1. Start from a tube that already works. If the tube in your wheel now works with your pump, the valve length its maker lists for it is a length you know fits. Compare like with like: Schwalbe states that its figure includes the valve foot, not just the part outside the tube, and another maker may measure differently.
2. Otherwise, measure the rim's depth at the valve hole, from the floor of the rim channel where the tube sits to the spoke-side face where the valve comes out. With the tire and tube off, push a spoke through the hole from the spoke side until its tip is level with the channel floor, mark the spoke at the spoke-side face, and measure from the tip to the mark. The depth rod on a pair of calipers does the same job.
3. Push your pump head onto a valve as far as it goes and note how much of the stem it covers.
4. Add the two. That sum is the least the stem above the tube can be, since the stem has to pass through the rim and still give the pump head that much to grip. The number on the box is longer than that part by the height of the valve foot, which Schwalbe doesn't publish, so a listed length only a little above your sum may still fall short. The next length up gives more margin, at the cost of more exposed stem.

Lengths on offer vary by size and maker. Schwalbe's No. 17 page lists 40, 50, 60 and 80mm; its No. 7S (20 inch, 451) lists 32 and 40mm. Continental's tube FAQ says its valves come in 42, 60 and 80mm lengths, and that a Schrader valve is shorter than a Presta. A tube page's length list covers all its valve versions, and not every pairing is offered: on Schwalbe's No. 10 page, 60mm can't be chosen with the AV valve. Past the longest valve offered, the Sheldon Brown tube article describes valve extenders; the kind that replaces the valve core needs a removable core. Schwalbe says the core in its tubes is always replaceable, but warns against converting older Aerothan tubes with black plastic stems to its Clik Valve because air may leak. Ask Schwalbe before fitting a core-replacing extender to one of those.

Before you order

• Both numbers of the ISO size, copied from the sidewall.
• Your bead seat listed on the tube, with your width inside its range, in millimeters where the listing gives them.
• A valve type that passes through your rim hole and suits your pump.
• A valve length, as that maker measures it, that clears the rim with room for the pump head and is offered with your valve type.

Check it on your own equipment

These take you to the manufacturers and standards bodies the page draws on, so you can look up your exact model.

• Manufacturer specification
  Schwalbe tube finder (opens in a new tab)Schwalbe's tube finder. Enter your tire size as ETRTO (e.g. 40-622), inch or French, choose a valve type (Schwalbe Clik Valve, SV, AV or DV) and a version (Aerothan, Aerothan Plus, Standard, Extralight or Air Plus), and it lists the matching Schwalbe tubes. Each tube's page spells out the sizes it covers and the valve types and lengths offered. It doesn't ask for rim depth, so valve length is still yours to check. — www.schwalbe.com
• Manufacturer specification
  Continental tube chart (PDF) (opens in a new tab)Continental's one-page chart, headed TUBES, listing each tube by the first and last ETRTO size it covers, such as Tour 28 All at 32-622->47-622/42-635 and Compact 20 at 32-406->47-451, with article numbers under Auto Schrader, Blitz Dunlop and Sclaverand Presta valve columns. — www.continental-tires.com
• Official support page
  Schwalbe valve FAQ (opens in a new tab)Schwalbe's notes on Dunlop, Sclaverand (Presta) and car (Schrader) valves: the 6mm and 8mm stem diameters, the warning that Presta tubes in larger rim holes often tear off, and the rims drilled 6.5mm on the outside and 8.5mm on the inside. — www.schwalbe.com