In 75% of my flats, i have not been able to find a cause. This makes me very nervous, because i usually carry only one spare tube. I got one this past weekend. I found the puncture in the tube, and I knew where it should be on the tire. I checked and checked and found nothing. I put in the new tube, and it is holding. It just makes me wonder what caused the puncture. It had to be sonething that went through the tire and tube and came back out. I wonder what could do that. I have seen pieces of a steel belt from a car tire. They're thin and sharp.

Glass and radial tire wires can actually hide inside the contact area of a tire and come out when the tire/tube is fully inflated.

Are you getting one hole in the tubes or two "snakebite" holes?

I usually dismount my tube and tire together. If it is a big hole, I can usually locate the flat before separating the tire and tube. Perhaps you could also mark the valve or I've heard of people matching the logo with the valve to help locate things like flats.

Also, keep in mind the rim and rimtape as possible causes.

It's nothing that unusual. I would guess that sometimes when a very small road hazard punctures a tube the force of the air escaping could blow it out of the tire. As long as you know the problem was a road hazard and you've searched the inside as well as the outside (some suggest a cotton ball or soft cloth that will catch on hazards) just remount the tire and tube.

I recently came across a bad batch of Geax tubes. They had thin patches and pores and cracks would open up spontaneously on inflation.

That's a really good reason to patch tubes. That and line up your tire label with (or opposite) the valve stem. Then if a hidden piece of glass causes a 2nd flat, it will be in nearly the same place and you know you have to find the culprit or get another tire and you know where to look. I've pulled out many pieces of fine wire about 2 mm long, some that lie entirely within the tread and casing with nothing showing. I'd never find them without 1) knowing it was there and would cause another and 2) knowing the location to within an inch.

Edit: so that wire is from steel belted auto tires? I've been wondering for years because it is a new phenomenon. I never saw it in until the '90s. My big mileage years were the '70s and I was riding tubulars and cheap. Those pieces of wire never crossed my eyes.

Ben

Stick a 2nd in your bag. They're cheap.

Those tiny pieces of wire can be a real headache. They are nearly invisible against the skin of the tire and can hide in the threads so that they only expose themselves when the tube is pressurized.

Right, I don't remember the metal wires in the past. I picked up a couple recently, and only found them by knowing where the flat was in the tire.

Periodically I'll use the leather punch from a Swiss Army Knife to probe the bottom of every hole in the tire for glass and debris. Squeezing a deflated tire may help.

I'm now using puncture resistant tires, and doing much better at avoiding flats than I ever remember, and think they're even picking up less glass.

However, I've heard that winter and wet tires is worse than summer dry tires... I hadn't thought about it earlier, but so far, that seems to be the case this year.

This is where they come from.

Are the flats on the outside of the tube(side that goes against the tire) or inside(side with valve stem that goes against the wheel)? If outside it's something getting through the tire. Take the tire off the rim and turn each section inside-out to see if anything pokes out of the carcass. If inside,it's the wheel or rim tape. Check your rim tape,the area around your valve hole,and run a cotton ball(or carefully use your finger) around the rim to see if anything snags. If there's two slits in the tube,it's a snakebite and you're not running enough pressure in your tires.