Symptoms
- Tire goes flat again within hours or a day of inflating
- Hissing sound near the valve or tire tread
- Bubbles appear when the submerged tube is checked in water
- Tube has a small hole even after a previous patch
Likely causes
- CommonSmall puncture not yet found or patchedTiny punctures from thorns or glass can leak slowly and be easy to miss.
- CommonFaulty or loose valve coreA worn valve seal or loose core lets air seep out gradually.
- PossibleWorn or missing rim tapeRim tape protects the tube from spoke nipples; if it shifts or wears through, the tube can develop a leak at that spot.
- PossibleOld, dry-rotted tubeTubes degrade with age and can develop tiny leaks throughout, especially at the seam.
What to do
- Inflate the tube outside the tire slightly and submerge sections in water, watching for bubbles to find the leak.
- If the leak is at the valve, try tightening the valve core with a valve core tool, or replace the tube if it doesn't seal.
- Check the rim tape is centered and fully covering the spoke nipples if the leak is at a spoke hole location.
- Patch small holes in the tread area with a patch kit, following the kit's instructions for scuffing and gluing.
- If the tube is old with multiple small leaks or seam damage, replace it entirely rather than patching multiple spots.
- Reinstall the tube carefully, making sure it isn't pinched between the tire bead and rim.
- Inflate to the recommended pressure and monitor over the next day to confirm the leak is resolved.
Tools and parts
- Bucket of water or spray bottle
- Valve core tool
- Patch kit or spare tube
Bike inner tubeSearch: “bicycle inner tube replacement”
Rim tapeSearch: “bicycle rim tape”
When to call a pro
A bike shop can quickly find slow leaks and replace rim tape if it's worn or improperly seated.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.