Inner tube

An inner tube is the rubber air bladder inside a tube-type tire. When it punctures, you can patch it or swap in a new one.

What it's used for

Park Tool suggests e-bike owners carry a patch kit or a spare tube, and ideally both, to cut downtime from flats (Park Tool e-bike tools). It treats a stick-on patch as a temporary trailside fix and says to replace that tube as soon as possible, while a glue-on vulcanizing patch is more durable (Park Tool tube repair).

What to look for

• The right size. Match the tube to your tire's size marking. Park Tool notes that tire bead diameter standards are not interchangeable (Park Tool tire guide).
• The right valve. The rim's valve hole must match the valve type. Schrader valves are about 8 mm across and Presta about 6 mm. A Presta tube can go in a Schrader-size hole with an adapter sleeve (Park Tool).
• Valve length. Presta valves come in different lengths, and deeper rims need longer ones (Park Tool).

Using it safely

• Find what caused the flat before fitting a new tube. Park Tool says to check the tread for nails, glass or thorns and to feel carefully inside the casing (Park Tool).
• Put just enough air in the new tube to hold its shape before fitting the tire, and make sure it isn't caught under the bead (Park Tool).
• Inflate to the range printed on the tire sidewall (Park Tool). See Set tire pressure.

Best price we found

• Kenda Standard 20 inch tube, 20 x 3.5 to 4.5, at Kenda's own store: $12.95, checked Nov 9, 2026

This size covers common 20 x 4.0 fat e-bike tires. When checked, the Presta valve versions showed available and the Schrader version showed sold out, so match your rim's valve hole. Prices change often, and a local shop may match them.

Videos

Guides that use it

• Fix a flat on a rear hub motor wheel
• Set tire pressure
• E-bike flat tire

Sources

• What tools do I need for my e-bike, Park Tool
• Inner tube repair, Park Tool
• Tire and tube removal and installation, Park Tool
• Kenda's own store: Standard 20 inch tube, 20 x 3.5 to 4.5, $12.95