At the Westminster, MD swap meet in February I picked up a mint condition Flying Pigeon roadster for the munificent sum of $50.00. Exactly as pictured, with a flat rear tire:



After a month of fettling (you wouldn't believe the assembly condition, every part was loose, except for the wheel bearing cups which were installed with an air wrench), I now understand why the previous owner was so desperate to rid himself of the bike. You can't ride it five miles without getting a rear puncture. On the inside (rim side) of the tube:



No spokes are protruding, the rim strip is in good condition, nothing fails the finger test all the way around the rim, and after the second flat I added a layer of electrical tape over the rim strip for extra cushioning (still rebuilding my shop, parts supply is short at present). I managed a 3.5 mile ride this morning and figured I finally had the problem solved. Took it out again this afternoon, barely got a half mile down the road and flat again.

The best guess I can come up with is that the tire bead isn't seating well enough allowing the tire to rotate on the rim (28x1/2 tire, 40-635 tube, 50lbs pressure - I don't run a rod braked roadster higher than that, my Raleigh Tourist has been known to occasionally blow the bead at 55lbs, wlll definitely do it at 60). Does anyone else out there either have a better idea, or confirmation of what I'm thinking?

I bet your rimstrip isn’t as good as you think it is. If it is rubber, replace it with cloth or something fiberous.

Is the puncture always occurring at the same location? Mark the location on the rim and look there. Could there be a sharp edge in the lip of the rim?

Look again for anything causing it, and fix.

Some old tubes can split easily. Replace it with a new tube.

That is a new tube. The second I've put on the bike. Two rides and approximately four miles on it.

You mention the "finger test" around the rim.

Have you done the same all around the interior of the tire itself? Might be a sharp object embedded in the tire that protrudes just enough on the inside such that the tube gets slashed.

There will be something there. It is up to you to find it.

I second that. Even with the added electrical tape the tube isn't protected enough. Electrical tape is thin. Try a cloth rim strip on top of electrical tape.

Are those single wall rims (whoops, my bad, I should have written double wall rims) with deep holes for spoke nipples? If so, thin rubber band type rim strips won't provide enough support. The tube will extrude into the spoke nipple hole and weaken, usually splitting just like the photo shows.

Try a cloth rim tape like Velox or other (they're all pretty much the same). Or a rigid plastic rim strip like Schwalbe sells. But the cloth tape works great.

The only trick with cloth tape is to avoid using tape that's too wide. If I climbs up the shoulders of the rim it can hinder seating the bead on some tire/rim combinations. I usually chose cloth tape just wide enough to cover the spoke nipple holes but no wider.

Sounds like the best idea so far. Will give it a try.

Did that immediately. That was my first thought. Then did the finger test down the rim, checking each of the spoke ends.

I’ve gone to using tubeless tape for both my tubed and tubeless rims. Tesa tape, I think #4289 is the stuff. I buy it from November Bikes. Was getting recurring punctures even with the good cloth stuff.

The bike was designed to fly less likely to get punctures while flying : P

I tend to use the fabric reinforced Continental rim strips to good result but I don't think they make them for your tire size however Velox or better yet Newbaums will work well or tubless tape if you need something lower profile.

Although infrequent, this has confounded me before. I found no sharp edges, no protruding spokes, and used quality rim strip ... i.e. no apparent fault. I found that running a strip or two of thin, fiber-reinforced packing tape tightly around the rim before I installed the rim strip solved the issue.

Run a cotton ball around the rim to check for sharps.

Looking at that cut the second thing that came to mind was a sharp edge on the rim strip.

Good luck. That is really frustrating.

A very productive evening for possible answers. Thank you. Will give a few of these a try once I'm done mowing the lawn this afternoon.

Your'e mowing already? I've got another three weeks here before even thinking about it. How is the new Grudge? Smiles, MH

If all the other advice fails try checking the area where the rim is joined together. I ruined a wheel on a tour and the replacement I was able to find. It would go flat after 30-50 miles. After patching it twice I finally was able to locate it on the rim. I did this by placing the logo on the tire in line with the valve stem. When the tire went flat I lined up the tube's valve and then searced both the tire and rim at the location of the puncture. I found a rough spot on the inside of the rim's joint. Using the sandpaper in my patch kit I sanded it smooth, and went another 1000 miles without a flat.

Another thing to check is that the rim tape/covering that is there now isn't slipping when you mount the tire. I had that happen to me with Velox tape that just slid to the side. And the thing I discovered then too is to not use tape that is too wide because when you put the tire on it protrudes from the side enough to slip with the friction of the tire against the tube while mounting. It worked fine when the wheel was new and for about 3 years, then I just couldn't stop the flats and that's what it was.

Ride with the same tube and patch it. This will give you a running record of where tie issue(s) is. (Remember, the cut is "n" spokes from theeh valve but can be in either direction.) My guess is that you will see the patches falling in near the same place (or directly beside each other if you hold the valve and pull the tube away from it). Now you know the issue is. Knowing exactly where to look makes finding an unknown much easier.

I patch tubes for routine flats whenever possible. For very small punctures, it tells me where to be looikng for that nearly invisible tire wire or tiny piece of glass or broken thorn, all of which can be entirely inside the casing waiting to cause the next flat.

Ben

Huh?

Zooming in on the rim, it looks like it has a fairly narrow central ridge where the nipple holes are. Sometimes when you have a rim profile that’s deep and narrow, the tube won’t fill the trench evenly. It’ll get hung up on the edges and then only the material earlier spanning the trench will stretch to the bottom of the trench. Whether it’s the localized stretch as such that pops the tube, or the thinness that makes it more sensitivite, I don’t know.
You have a couple of options if you want to research this route:
1) make sure to use the widest tube possible
2) inflate slowly, giving the tube time to creep into the crevasse
3) use some talcum powder, corn starch etc on the inside of the rim to encourage creep
4) if you don’t need the trench to get the tire on, fill it. I’ve got an old Dutch bike with a similar rim profile that had a length of rope as filler. Not a great choice of material b/c of water retention and long-term survival of the rim, but sound in principle. If I ever find a less rusty replacement rim I’d probably use a length of transparent fuel hose of the right size instead.
5) or deck it over. I’d probably use something sold as a tape rather than something sold as a rim strip. Duct tape with a long-lasting adhesive cut down to width for example.

My mistake. I should have written double wall rims with deep spoke nipple holes where the base of the nipple isn't flush with the inside bottom of the rim trough.

Soft rubber rim strips and tubes can extrude into the holes, forming dimples that weaken the tube and eventually splitting at the tips of the dimples. It happens less often with single wall rims where the base of the nipple is closer to flush with the rim trough.

Switching to cloth tape solved that problem with all my wheels, single and double wall rims.

See these threads:
Rim side tube puncture: No spoke or removed tape

Tube failure on inner side, no puncture, rim strip good

Weinmann LP18 Geometry Causes Flats?

I got a bit hesitant there whether it was a typo or if you’d found some truly odd rim design somewhere.

Bingo! It seems to work. Patched the tire yesterday, inflated it and let it sit overnight. Did one layer of reinforced packing tape over top the layer of electrical tape. Mounted the wheel this morning (I've gotten to the point that I can do a rear wheel on a rod braked roadster almost in my sleep), and did two rides today totaling 11 miles with no problem.