Start with where the hole is
When a tire goes flat again and again, the cause is usually something the repair missed. Replacing the tube without finding out why it failed often just repeats the problem. The location of the damage on the old tube is the best clue you have.
- A small hole on the tread side usually points to something sharp that went through the tire, such as glass, a thorn or a piece of wire.
- Two small holes side by side (often called a snakebite) usually point to a pinch flat, where the tire compressed against the rim.
- A hole on the rim side often points to a problem inside the wheel, such as worn or misplaced rim tape or a sharp spoke end.
- Damage near the valve may be a valve problem or a tube that was twisted or pulled during installation.
- No hole at all may mean a leaking valve core or a leak at the valve stem. Our guide to slow leaks and why a bike tire loses air covers how to track those down.
Common causes of repeat flats
Debris still stuck in the tire
A tiny shard of glass or a thorn can stay lodged in the tire and puncture each new tube. Carefully run your fingertips along the inside of the tire, ideally wearing a glove or using a cloth so you do not cut yourself, and check the tread on the outside too. Remove anything you find with a small tool. Compare any object with the position of the hole in the old tube.
Rim tape problems
Rim tape covers the spoke holes inside the rim so the tube is not pressed against them. If it has shifted, worn through or is too narrow, the tube can be damaged from the inside. Check that the tape fully covers every spoke hole and sits centered. If it is cracked, loose or moved, replace it.
Pinch flats from low pressure
If a tire is too soft, a hit on a bump or pothole can squeeze the tube between the rim and the obstacle. That typically leaves the paired holes described above. Riding at a sensible pressure for your tire and weight helps. Tires usually have a recommended range printed on the sidewall. See our article on how to tell if your tire is flat or just low for a quick way to check your pressure by feel, though a gauge is more reliable.
Cuts and worn tires
Look closely at the tire for cuts, bulges, cracked rubber or worn tread, and check the sidewalls. A cut can let a tube push through or let debris in. A tire in poor shape is a common reason people keep getting flats, and replacing it (see how long road bike tires last for warning signs) may be the better fix than another patch.
Valve and tube issues
A loose valve core can let air out slowly. On many Presta and Schrader valves the core can be tightened with a small tool, but not all valves have removable cores. Also check that the tube is the right size for your tire and rim, since a tube that is badly mismatched or folded during installation can fail early. When refitting, make sure the tube is not pinched under the tire bead.
Patches that did not hold
A patch can fail if the surface was not clean and dry or if the glue was not given time to cure as directed by the patch kit. If a patched tube keeps losing air, replacing the tube is often simpler.
A simple order of checks
- Find the hole in the tube (inflate it and listen, or hold it under water and watch for bubbles).
- Match it to a spot on the tire and remove any object.
- Inspect the inside and outside of the tire for cuts and wear.
- Check the rim tape and the inside of the rim for sharp edges or protruding spoke ends.
- Check the valve and valve core.
- Fit a new tube, inflate slightly, make sure it sits evenly, then inflate to a suitable pressure.
- Re-check after a day to see whether it holds air.
Preventing future flats
- Keep pressure in a suitable range. Check it regularly with a gauge, because tubes lose some air naturally over time.
- Inspect the tires now and then. Pick out small embedded debris before it works its way through.
- Consider puncture-resistant tires, tube liners or sealant. These can reduce flats for some riders, though none eliminates them.
- Consider tubeless. Tubeless setups use sealant to plug small punctures. They need a compatible rim and tire and periodic sealant top-ups, so check the manufacturer’s guidance first.
When to replace the tire or get help
If you have fixed the obvious causes and the tire still goes flat, the tire itself may be worn, or there may be an issue with the rim that is hard to see. A bike shop can inspect the wheel and tire quickly. If the tire or rim looks bent or uneven, see fixing a warped or bumpy bike tire.
FAQ
How many flats are normal?
There is no exact number. Many riders go months without one, while riding on debris-heavy roads can mean more. Repeated flats within a short time usually point to a cause worth finding.
Why does my tire keep going flat when there is no hole?
Often the air is escaping at the valve, through a loose valve core, or around the bead on a tubeless setup. A leak can also be hard to see until the tube is inflated and checked in water.
Can I fix a flat without removing the tire?
Some sealants can be added through the valve and may seal a small puncture, but this is usually a temporary measure. To find and fix the real cause, the tube normally needs to come out.
Should I replace a tire after repeated flats?
If the tire has cuts, cracking or obvious wear, replacing it is sensible. If it looks fine and you have removed the cause, it may not need replacing.