Flat tires are a normality of cycling: You simply can't ride a bike for long without getting a flat. Strong tires, correct inflation pressures and conservative riding help to decrease flats, but at some point, you're likely to pop a tube. Look for these issues when changing your tube to help avoid flats in the future.
Punctures are a common problem on rough or dirty streets. Glass, metal, sharp rocks and even plastic waste can push through the tire wall and cause a leak. This type of flat can be quick or slow to leak, so check your tire pressures regularly if you've been riding glass-strewn roads. When changing a punctured tube, carefully inspect the inside of the tire and remove any sharp object that may have caused the flat.
Pinch flats are caused by a fold in the tube that becomes stressed and eventually breaks. These flats are fast-leaking and often cause a large gash in the side of the tube. To combat pinch flats, check along the inside of your wheel rim to make sure you haven't pinched the tube between the tire and rim, and keep your tires inflated to their recommended pressures.
Over- and Under-inflation
Incorrect inflation can also cause flats. Over-inflating your tires can cause them to spontaneously burst, often leaving a hole in the tire sidewall and ruining the tire. Under-inflation can cause pinches and riding instability. Also, keep in mind that air expands as it gets warmer, so leave extra room in your tires on warm days to allow the air to expand.