A question for the experts here. Is there a way to determine the cause of the flat by looking at the inner tube hole? I am always very carefully checking the inner tire walls and today again I didn't find anything that would have caused the flat. I was just riding down the street, and I thought pinch flats usually occur when you jump curbs or run pot holes (in other words, causing sudden stress on the inner tube).

Is the position (on the tube) or hole shape/size different for pinch flats vs flats caused by debris?

Thanks much.

Never had a pinched flat 28,000 miles. I did have 28 flats last year.
The pinched ones I have seen come in two's. The tire gets low and when it hits bottom = pinched flat.

Had multiple flats from tiny pieces of glass that was most difficult to find.
Sometimes you have to turn the tire inside out to find it.

This might help. See page 12 & 13 of the book here: https://freebikebook.blogspot.com/

While riding in the rain one nite I hit a pothole covered with water at medium velocity.
Air came out of the tube and I just swapped it out with a new tube. Next day I checked
the flattened tube and there were 2 small holes next to each other, classic pinch flat I suppose.
Quite different than the normal single hole I get with flats from glass and other debris.
I've had over a 20 flats, I think twice I never found the debris that caused the puncture.

Thanks everybody for the responses. The free bikebook is help, thank you scroca.

1nterceptor, are you saying that you always found what caused the debris, except of two occasions?

That's correct. Usually it's a piece of glass embedded in the tire, sometimes small pieces of metal
like the pointy part of a thumb tack. But there were 2 occassions that I couldn't find the debris that
caused the punctures. I hate it when that happens, because if I patch the tube and
if I missed the cause of the puncture and it's still there; it might give me a flat again. I'm thinking that
it maybe possible that whatever got my tire may have been embedded in the asphalt or that it may
have fallen off after a few turns of the wheel.

The pinch flat is caused by low tire pressure. The tube is pinched against the rim, it looks like a snakebite, usually with 2 parallel punctures the width of the rim. Most often happens on my mountain bike.

I once returned from Mountain Biking in West Virginia, tire still inflated when I rode back to the house where I was staying. The next morning my tire was flat. I actually had 3 punctures picked up on the trail that were so tiny that all three of them together only amounted to a slow leak. Culprit: Tiny hair-like thorns that are so soft and willowy you couldn't manage to prick your finger with them if you tried. But when they get in your tire and work their way through such that just the tips protrude through the casing, the tire itself gives them enough support to puncture.