Avoiding a Pinch Flat

David Fiedler

A pinch flat is a different situation than running over an object like a nail, a piece of glass or wire that actually punctures your tire. (Though these types of punctures are quite common for anyone who cycles with any regularity, there are easy ways to reduce the number of flats you get from these causes, too.)

A pinch flat is when you hit a sharp edge with your bike tire had enough that it presses and pinches your inner tube against your rim hard enough to perforate the tube and cause a flat tire.

A pinch flat is distinctive because there are usually two small holes side-by-side in your inner tube in a snakebite pattern. This comes from the two parts of the rim where the tube has been pressed against it. 

Of course, if you get a pinch flat, the next thing that you'll need to do before you can resume riding is to fix your flat tire.

Proper Inflation is Key

A pinch flat is much more likely when your tires are under-inflated. Hitting potholes or crossing a railroad track are common causes of pinch flats because of the crisp edge that can pinch the tube when struck.

Certain types of bike tires are more vulnerable to pinch flats.  Skinny road bike tires, for obvious reasons, are more prone to getting pinch flats.  Despite their very high air pressure, the fact that there is so little tire there to protect the tube from getting pinched against the rim makes pinch flats happen more frequently, even when they are properly inflated.

Follow These Steps

  1. The first thing you need to know is the proper air pressure for your tires. This is found as information printed on the sidewall of the tire. Generally, it will be reported as PSI, which stands for "pounds per square inch) or kPa, which is the metric unit for measuring pressure. 
  2. Once you know what the recommended tire pressure it, the next thing is to use a bike tire gauge to measure the tire's actual current pressure.  Obviously, if you can tell the tire is flat just by looking at it or if it feels very mushy, you will know that you need to put more air into it.
  1. Also, your tire will either have a Presta valve or Schrader valve.  This is important to know to ensure you have a compatible inflation fitting.  You may need to get an adapter (available for about $2.00 from your local bike shop) if you have a Presta valve and plan to use a standard compressor fitting that fits car tires, etc.
  2. If the tire pressure gauge indicates that your pressure is low, you can use either a bike tire pump (such as a floor pump or a smaller frame-mounted pump) to inflate your tires. Or an air compressor like you might find at a filling station is another good option.  Just beware that the higher pressure pumps can quickly overinflate your tires (even to the point of bursting) if you aren't careful.
  3. Alternate between putting air into the tire and measuring the air pressure with the gauge until you get at or near the proper inflation level.
  4. Finally, please know that bike tires in general will leak over time.  Even if you don't have an actual puncture, you will likely need to add more air from time-to-time to maintain the proper pressure.  Road bikers who have the high-pressure tires generally pump up their tires before every ride.