I have an older 25c Vittoria Rubino on the rear with app 3500 miles.
I brought the tube up to 115 this morning, which is what I always run it at.

Along the ride I started to "feel" the rear sag. I hit a small bump and really felt the rim take the shock. I pulled off and checked. Sure enough it was going flat.

I hit it with a CO2 pump and brought it back enough to get to work that was at 8 a.m.

I just checked, 2:50 pm, and it is soft as a baby's butt, but not flat.

This is the second tube in four days. The first one also developed a small slow, painfully slow leak. I thought maybe it was the Bontrager tube, cause I usually use Kenda, but after this little thing I am thinking that some small particles are getting into the tire and abrading the tube enough to cause small, slow leaks.

Would this be a correct assessment?

When I checked the tire and rim during the reinstall of the new tube I ran my fingers backward and forward along the underside of the tire. I checked the rim track and did not find anything on either surface.

I am going to limp home unless it would be worth my time to find the leak and attempt a patch.

BTW, that CO2 pump is fast!!!

Have you identified what was causeing the flat in the first place? find that, fix that issue, and you should have no more flats from that area.

if you inflate the punctured tube, you will find the place with the hole in, match that to the rim (this is why the tire logo should be aligned with the valve hole) to find the area on the tire that has been penetrated / is damaged.

[/QUOTE](this is why the tire logo should be aligned with the valve hole)[/QUOTE]

Good tip. I did not know that.
No I have not been able to ID the holes. I inflated the tube that I took out and, while slightly deflated, it is still holding air, but I cannot find the leak.

I'll give the tube hole a go.

With the tire off, go around it, squeezing the tread area with your thumbs. Usually you'll see a cut or some damage. Inspect the cut for a bit of glass or rock. Usually you can flick it out with the point of a knife, but be careful not to do more damage to the tire. Then look on the inside of the tire to see if it came through at all. That might be your problem.

To find the leak in a tube, blow it up until it's pretty big. For an ordinary road tube, until it's about 1.5" in diameter. Then go around it, spinning the tube with your mouth open and the tube between your lips. Usually you'll feel the leak with your lips. If that doesn't work, immerse part of the tube in a sink full of water. Go around, spinning the tube in your hands, and wiping off bubbles that stick to the tube. You'll eventually see a stream of bubbles.

The other thing to check is, once you've found the leak, if the leak is on the inside of the tube. If that's the case, there's a problem with your rim tape. A bit of metal could be poking through the rim tape and puncturing the tube.

In 60 years, I've never had a flat from getting a bit of dirt in the tire while changing a flat. I suppose it's possible, though.

Another possibility is a bad valve. Rare, though. Very common to have a leak at the base of the valve stem, where it's joined to the tube. If so, toss it.

A real sensitive way to check the tire and rim for sharp spots is to run a cotton ball around. It will catch on the slightest sharp or rough spot. If you suspect an embedded object in the tire try turning the tire inside-out before checking. Having the inside of the tire under tension will tend to open up any small holes which are there and make them easier to find.

Let me suggest another hypothesis, based on the pressure you are using and the slowness of the leak. You have a small hole in your tire's carcass. At high pressure, the tube comes through this hole comes in contact with the road surface and punctures. As the pressure reduces the tube partially withdraws from the small hole in the tire but not completely. This partially closes the puncture and you continue riding on what appears to be a reasonably inflated tire.

When you line up your tube puncture with your tire, also check for a tiny hole in the tire carcass, in addition to a sliver of glass or metal embedded in the tire.

SBinNYC hit the nail on the head.

I found a small bit if wire on the inside of the tire. It was thinner than a staple. The hole in the tube was smaller than a needle.

I patched it and filled it. Interesting to note that CO2 pumps do not fully inflate the tube. I had o top it off at the LBS. Of course this is my first time using the contraption.

Also my tires are full of holes, cut, gashes, and other nicks. However, the tire is still ok and this is first real trouble I have had with it.

I run it at 115 in the rear because the Vittoria bounces too much at higher pressures.