Is it really leaking?
All bike tubes lose some air over time, and lightweight tubes tend to lose it faster. A tire that needs a top-up every few days may be normal. One that is noticeably soft after a night or after a single ride likely has a leak. If you are unsure, see how to tell if your bike tire is flat or just low.
How to find the leak
- Inflate the tire to a normal riding pressure.
- Listen and feel. Move slowly around the tire, valve and rim.
- Use soapy water. Brush or spray it around the valve stem, along the bead where tire meets rim, and over the tread. Bubbles show where air is escaping.
- Submerge the tube. If the tire has a tube, remove it, inflate it a little and pass it through a bowl or tub of water, watching for a stream of bubbles. Mark the spot.
- Check the tire. Compare the hole’s position with the tire, and feel inside for thorns, glass or wire.
Common sources of slow leaks
- Valve core or valve stem. A loose core can seep air. Some valves let you tighten the core with a small tool; if bubbles continue, a new tube may be easier.
- Tiny puncture. A small thorn or sliver can cause a slow loss that takes hours to notice.
- Rim tape or rim issues. A worn or shifted rim tape can allow a spoke hole or sharp edge to damage the tube.
- Old or damaged tube. Tubes can wear, develop weak spots, or split at a fold from installation.
- Poor valve seal at the pump. Sometimes the leak is when pumping, not in the tire. Check the pump head is fully seated, and that a Presta valve is unscrewed and closed again after.
- Tubeless leaks. Air can escape at the bead, through porous sidewalls, or at spoke holes or valve seals if the rim is not taped well. Sealant also dries out over time.
Fixes by setup
Tube tires
Patch the tube following the patch kit instructions, or replace it. Remove whatever caused the hole. Check the rim tape and the inside of the tire before refitting. If the same tire keeps going down, work through why your bike tire keeps going flat.
Tubeless tires
Add fresh sealant if it has dried out. Sealant life varies by brand and conditions, and many manufacturers suggest topping up every few months, so follow the product’s guidance. Check that the tire bead is seated all the way around, and inspect the valve and rim tape. Small sidewall seepage often stops once sealant coats it; larger cuts may need a plug or a new tire.
Why a tire can lose air with no visible hole
The hole may simply be too small to see. Other causes include a leaking valve core, a poor seal at the valve stem, a tube slightly pinched at the bead, or a tubeless tire seeping at the bead. Soapy water is the easiest way to find these.
Cost and when to see a shop
A new tube or a valve core is inexpensive, but prices vary by shop and location, so ask for a quote. If the valve is part of the wheel or you cannot find the leak, a bike shop can usually check it quickly.
FAQ
What should I do if there is a leak in my tire?
Find where it is with soapy water or by submerging the tube, then patch or replace the tube, or add sealant for tubeless.
Why is my tire deflating with no hole?
Often the valve, valve core or bead is the source. These leaks are small and easy to overlook.
Can I just keep pumping it up?
For a short time, but riding on a leaking tire at low pressure raises the risk of pinch flats, and the cause will not go away by itself.