Gravel bike inner tubes: 700, 650B, butyl, TPU

What size inner tube for a gravel tyre?

Gravel tyres fit two diameters: 700, the most common, and 650B, chosen for small frames or to run bigger-volume tyres for the same wheel diameter. Their width generally ranges from 35 to 50 mm. A tube covers a range, for example 700 x 35-45 or 700 x 37-50: a 700 x 40 tyre, the most widespread section, fits both. Avoid stretching a thin tube beyond its range, as it gets thinner and punctures more easily.

As for the valve, gravel bikes almost always run Presta. Measure the rim depth: a 40 mm valve suits shallow rims, 48 mm the usual gravel profiles, 60 mm and more deep carbon rims. The valve must stick out far enough for the pump head to grip it properly.

Butyl or TPU: which tube for gravel riding?

• Butyl: the classic tube, stretchy and affordable. It tolerates small fitting errors and is repaired with an ordinary patch.
• TPU: a thin-walled thermoplastic polyurethane, several times lighter than a butyl tube and far more compact when folded. It has its place in the saddle bag as a spare tube, or in the tyre to lighten the wheels.
• Thick or reinforced butyl: heavier, it better resists pinch flats on stones, useful for loaded touring bikes.

A TPU tube is repaired with patches designed for this material, as the glue of classic patches does not hold well on it. On a rim with rim brakes, which heats up on descents, follow the manufacturer's instructions: some TPU tubes are for disc brakes only.

Gravel punctures: pinch flats, flints and puncture-resistant tubes

Off-road, two kinds of puncture dominate. A pinch flat happens when an underinflated tyre bottoms out on a stone or an edge: the tube gets trapped against the rim and splits with two small cuts, the classic snakebite. Holes come from flints, thorns and brambles along the trail. Against the first, the answer is a pressure suited to your weight and the terrain; against the second, a tube pre-filled with sealant plugs small holes within a few turns of the wheel. No tube replaces a tyre with protection under the tread.

Gravel bike tubeless vs tube

Tubeless, with no tube, has become widely established in gravel riding: it runs lower pressures without pinch flats and the sealant plugs small holes on its own. The tube still has two roles, though. It remains the simplest solution for those who ride little or do not want to maintain sealant, and it serves as a backup when a cut is too large to seal. In that case, remove the tubeless valve, wipe away the sealant, take out the thorn or flint left in the tyre, then fit the tube.

Tyres, repair and tubes for other types of riding

A new tube will not solve repeated punctures if the tyre is worn: see our gravel tyres, and gravel wheels for a switch to tubeless. Pumps, patches and tyre levers are on the pumps and repair page. MTB inner tubes and the general bike inner tubes page cover other bikes.

Which gravel inner tube brand should you choose?

Hutchinson, the French tyre maker, offers Gravel tubes with a 48 mm Presta valve, a 700 x 37-50 tube and TPU tubes to save weight.

Slime pre-fills its tubes with a sealant that plugs small holes; the 700 x 28-35 Presta version suits narrow gravel tyres, and a 700C tube for 35 to 43 mm completes the range.

Schwalbe covers 700 x 28 to 47 mm tyres, that is most gravel sections, with its SV17, with a 40, 50 or 60 mm Presta valve.

Michelin gives its Protek Max a bumpy shape: the tube works in compression, so a hole tends to close up, and a preventive sealant plugs the puncture. One version covers 33 to 46 mm tyres in 700.

Pirelli places SmarTUBE TPU tubes, in 700C as well as 650B, under the Cinturato name, its gravel and all-road family.

Tubolito makes only TPU tubes: its CX/Gravel line, for 32 to 50 mm tyres, comes as the S-Tubo, the lightest, designed as a spare, and the X-Tubo, reinforced against punctures.

Inner tubes on sale

Multipacks and tubes from older ranges join the road outlet, which also covers gravel, while new arrivals present the models that have just been listed. Make the most of the winter sales to build up a stock of tubes before the new season.

Frequently asked questions

Which inner tube does a 700x40 tyre need?

A 622 mm diameter tube whose range includes 40 mm, for example 700 x 35-45 or 700 x 37-50, with a Presta valve the right length for your rim. A 29-inch MTB tube, of the same diameter, also fits if its range goes down to 40 mm.

Can a TPU inner tube be repaired?

Yes, with patches designed for TPU, self-adhesive or supplied with a specific glue. Clean the area, apply the patch to the deflated tube and let it set before reinflating. For a long ride, carry a new tube instead.

What tyre pressure with an inner tube on a gravel bike?

The right pressure varies with the tyre's section, your weight and the terrain, within the range shown on the sidewall. With a tube, keep a little more pressure than with tubeless to avoid pinch flats, then adjust in small steps over your rides.

Can you put a tube in a tubeless-ready tyre?

Yes. A tubeless-ready tyre takes either a tube or sealant. If the tyre has already been ridden tubeless, remove the valve, wipe away the sealant and check the inside before fitting the tube.

Does a 650B tube fit a 27.5 inch tyre?

Yes: 650B and 27.5 inch correspond to the same 584 mm diameter. Just check that your tyre's width falls within the tube's range, as 650B gravel tyres are often wide, around 47 mm.