I have a IRO Mark V frame with Paul Component 32h track hubs laced to Velocity Deep V rims. I am using 700x28c Bontrager Race Lite Hardcase tires with 700x21-28c long-stemmed Specialized tubes. I am going out after work to buy what is my third tube for my rear in under 20 miles of riding. Front tire is fine. Each time I filled the rear tire the night before and went riding the next afternoon. Pressure didn't seem to noticably diminish overnight and only when I rode 3-4 miles did the pressure drop off. What am I doing wrong here?

Expect 1 more mine come in sets of 3

Just wanted to add that I filled both tires to 100 psi.

Could be that you never got the puncturing thing out of the tire. I had a tiny piece of copper wire in a tire that was almost impossible to find by touch much less by sight. It was so sharp that it made just a tiny hole and it leaked over the course of several hours.

Also, check the rim strip. If it slides off a nipple hole, the tube can bubble into it and burst.

Are they puncture flats or pinch flats? If they're puncture flats it's bad luck. If they're pinch flats, my guess is that the tires are underinflated, even if your pump says otherwise. Maybe borrow a friend's pump or cheat a bit more air in there.

Aside from finding any debris on or near the tube is there any other way to tell the difference between a puncture and pinch flat?

pinch flat looks like a snake bite. 2 holes very close to each other

I had a similar experience. Turned out my rim tape had shrunk slightly and a nipple hole was opened enough to allow the tube to become pinched when it was under pressure. I became obsessive about making sure my tire label, stem and drive side relationship was the same every time I changed tubes or tires so I could locate a difficult to find source for the puncture. If your leak is in the same place on your tube in all cases look for bad rim tape or a thorn in your tire.

Puncture is typically a hole and in the area where the tire tread meets the road, or over a spoke nipple. Make sure to install the tire with the label at the valve stem every time. This way, when you find the hole in your tube, you can match that area up to the tire easily to look for debris. Run a cotton ball along the inside of your tire in the area where the hole in the tube is. The cotton will often snag on the debris in the tire.

Pinch flats are usually longer and on the side of the tube where the tire/rim meet.

Hey the cotton ball is a good trick, thanks.

First thing you need to know is where on the tube is the leak, rim side, tread side, valve stem, or side wall. Put some air in the tube and hold it under water and look for bubbles. Index the tube to the rim, as jsharr said.

Al

Be sure to mount your tire in the exact same spot each time, find out where the leak is in the tubes, and if it is in the same spot, either it is the rim tape or something on the tire itself. I usually center the label on the tire with the valve stem, on the drive side.

never rule out just luck. It does happen some time, and it does suck, but there isn't anything you can do about it.

My record is 8 flats (all different, at least I think) in 30 miles.

The most difficult flat causing material is the radial tire wire that gets on the road when a truck tire comes apart. The first time I came across it I had two flats in a short time and only found the culprit when I wiped the inside of the tire with my finger and drew blood.
The tire label by the valve stem is a good idea to help you find the cause.

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+1 on this. I had the same thing where I got no flats for about three months then two in three days. Took the tire off and turned it inside out and found a tiny piece of wire sticking out far enough to put a hole in any new tube I mounted.

You said you bought new tubes. Do you not like to fix flats, or were the holes too bad to fix, or in a difficult-to-patch location on the tube?

(and as suggested, were the holes in the same place both times, or different places?)

I think I found the problem. After taking off the tube and running my hand along the inner edge of the tire I found a very small wire peeking through. Thanks for all the help guys.

I rotate tubes and put patches on when I can find the time. To be honest though tubes are cheap and I don't get a lot of punctures so there's not a huge motivation to patch them apart from being a good green citizen.

Yeah, those things are annoying. Just as annoying is when you get a tiny cut in the tire- not big enough to let the tube pop through, but big enough to let the tube rub on the pavement. You get a flat, stop, fix it, and go on your merry way. 20 miles later you get another flat, thoroughly check the tire, don't find anything, fix the flat, and go on your merry way. 20 miles later you get another flat, frustratedly check the tire, don't find anything, fix the flat, and go on your merry way. Etc. Etc.

I've had this happen twice in my life. Once was enough. Twice was the Revenge of the Flat Gods.

I had a similar experience years ago with a set of Mavic Cosmic rims. I finally realized that the Michelin rim tape that came on them had split over the spoke nipple recesses. The tape actually resembled strapping tape used in packaging. These tiny splits would only spread open when the tube was inflated. When the tire and tube were dismounted, the splits would close up and were invisible. You can imagine how this drove me crazy until I figured it out. Replaced with cloth tape and the problem went away!

I had one tire that I had to throw out after 4 flats. I knew to within the area of a quarter where the problem was. I've used the tire label by the stem trick ever since I read it on Sheldon's site many years ago. But the wire or thorn or glass that was causing it would retract back into the casing and I could not find it for the life of me. All the poking and prodding in the world would not get it to peak out and be removed. After the third one I thought it had fallen out on it's own or from my bending and prodding but then I got a fourth flat. That was the last straw and I tossed it and bought a new tire. The darn thing was only a few months old too!

When you do this, go around the tire both ways. I had a wire in my tube a month ago that was pointing along the tire, and almost missed it completely.