Quick checks: look, squeeze, listen
A flat or very low tire is usually easy to spot, but a partly soft one is less obvious. Start with these checks.
- Look at the shape. A properly inflated tire has a round profile. A soft tire flattens or bulges at the bottom where it meets the ground, and the rim sits closer to the ground than usual.
- Squeeze the sidewalls. A firm tire barely gives. If you can press the sides in easily or feel the rim underneath, it is low on air or flat.
- Look for damage. Check the tread and sidewall for a nail, glass, a cut or a bulge.
- Listen and feel. A fast leak may hiss. For a small one, add some air, then hold the tire near your cheek or ear while rotating it slowly to feel for escaping air.
Squeezing is only a rough guide. A tire pressure gauge gives a far better answer, and tires usually show a recommended range on the sidewall. If you have a Presta valve, unscrew the small tip before pumping or checking pressure.
Low on air or actually flat? The pump-and-wait test
Because tires lose a little air over time, a tire that feels soft is not necessarily punctured.
- Inflate the tire to a suitable pressure for it.
- Check it again after a few hours, or overnight.
- If it has barely changed, it was probably just low. Check pressure more often.
- If it is clearly softer again, there is likely a leak. Compare how fast it drops: a puncture can leave it flat in minutes, while a small leak may take a day or more.
Our article on slow leaks and why a bike tire loses air helps you find where the air is going.
If it will not hold air
If the tire will not stay inflated, the cause is usually a puncture, a leaking valve, or a tube that has come out of shape. Inflate it, then check the valve area, tread and sidewalls. For a more thorough check, remove the tube, inflate it a little and hold it under water, watching for bubbles. If the same tire keeps going down, see why your bike tire keeps going flat.
What to do next
- Just low: pump it up to a suitable pressure and monitor it.
- Flat with a visible cause: remove the object carefully and repair or replace the tube.
- Flat with no visible cause: check the valve, rim tape and inside of the tire.
- Not sure it is safe to ride: if the tire is damaged, bulging or cut through, avoid riding on it until it has been checked.
FAQ
Can a flat tire just need air?
Yes. Tires lose some air gradually, so a soft tire may only need pumping. If it goes soft again quickly, there is probably a leak.
What should I do if my bike tire is flat?
Check for the cause, then pump it up or remove the wheel and repair or replace the tube. If you cannot fix it, walking the bike or getting help is safer than riding on a flat tire, which can damage the tire and rim.
How can I avoid flat tires?
Keep pressure in a suitable range, check tires for embedded debris and wear, and consider puncture-resistant tires, liners or sealant. See our guide to stopping repeat flats.