How can I patch a hole on the underside of an inner tube?

Question

Is it possible to patch a hole on the underside (rim side) of an inner tube? I have not had success doing this. Is there a special technique?

Answer 1

It does not matter on which side the hole is, the process is exactly the same anywhere on the tube. Be sure to let the glue become more viscous and sticky by waiting for a while before applying the patch. Wait long enough before inflating.

Only if the hole is too close to the valve (milimetres), it may be impossible. But it is the same anywhere else.

If you are not successful, you will have to show us more about the tube and the steps you are doing. Please also show in which way your attempts fail.

Answer 2

I've never had a problem with patching a hole based on where around the tube it was. Location only seems to be a problem if the hole is near a seam/rib, or very close to the valve stem.

The techniques are

1. Abrade the area around the puncture - that's what the sandpaper/file is for. You want to roughen it, but not thin it.
2. Apply the solvent thinly but over an area larger than your patch
3. GO AWAY FOR 5-10 MINUTES seriously this is the step people seem to miss. In the old days it would be "go have a smoke" but now it might be "go check your phone" The liquid is not a glue, it is solvent melting the rubber slightly, and this takes time.
4. After that break the solvent should not look wet. Slightly inflate the tube to the diameter it would be inside your tyre and immediately peel the foil backing off the patch. Avoid touching the shiny surface and hold it by the clear plastic fronting. Slap your patch onto the hole.
5. Use a roller, brayer, or some kind of rounded surface like a coin or the tip of a thumb to press hard on all areas of the patch.
6. Inflate tube to about 5 PSI, it will start to stretch, and the plastic backing will peel loose. Leave tube inflated for a couple hours as a check before reinstalling.

One hard-to-spot cause of problems is poor quality patches. The cheap "50 for $1" packs are not worth it, and getting better patches helps enormously. I like the "cure secure" ones which are thin and camouflage into the tube.

The janky asian patches are only good for booting inside a tyre IMO.

Answer 3

There are exactly two things that need to be done right when patching a tire.

1. Apply the patch properly. Roughen the inner tube around the puncture properly (to a uniform "dark black" (Karl Valentin) charcoal-like appearance) over an area that's larger than the patch. Apply glue to an area that's larger than the patch, too. Because the patch peels from the edge, so you want the edge to stick extra well and not suffer from insufficient roughening or glue. Pinch the patch on real hard, the quality of the patching depends on the applied pressure.
2. Make sure to find and eliminate the reason for the leak. This cannot be stressed enough. On the street facing side that's a shard or a thorn; on the rim facing side, that's a damaged or misaligned rim band or a damaged rim or a spoke that's poking through. If you don't see at least a hole where a splinter can have poked through chances are you are missing it and will have to repeat the procedure soon.

Answer 4

One tip I can add to the other answers is that patching on the rim side (especially of thin tubes) it can be helpful to flatten and slightly stretch the tube by clipping it to something flat. That will prevent the join from wrinkling or the tube sticking to itself while you're smoothing things down, and give you something to push against.

I don't usually bother but for the best patching I use a thin wooden board or a stiff ruler, with clothes pegs or similar spring clips to hold the tube out flat before I start. Some tubes seem to take patches better than others, even though I only buy the default butyl tubes.

If patching at the roadside (something I try to avoid, but I've had 4 punctures in a day before, and only carry 2 tubes), I tend to squat or kneel on one knee, and use my thigh as a work surface. Check for sharp things first, but you can stretch the tube out a little by trapping against the ground with your foot. Fins a comfortable position before starting, as you'll be there for a few minutes.

Answer 5

There is a good(but wrong) reason why someone would consider a rim-side hole un-patchable. Ordinary punctures are usually caused by extremely tiny thorns, rim-side punctures are always caused by a spoke penetrating the tire. A spoke is ... larger than a thorn.

Yes, you can patch it. All the other advice is awesome and smarter than what I can ever produce. The only addition I would make is to consider the patch size. Purchase patches instead of using an old cut-up tire or 10 years old patches. Apply all the advise. Use larger patches for larger holes. It will work.

Another rather controversial advice is to patch the tube, wait for 5 minutes(pressing the patch hard), install it on the bike and pump it up to operational pressure. This stretches the rubber joint while it's semi-hardened.

Answer 6

Is it possible to patch a hole on the underside (rim side) of an inner tube? I have not had success doing this. Is there a special technique?

There is a special technique.

Use only glue-type patches (never glueless patches), roughen the area on the tube with a piece of sandpaper (if the patch kit had a "cheese grater" throw it away and replace with real sandpaper), and do not use the tube for a day after patching.

The last bolded advice is the important one here, I believe. You should always carry a spare inner tube. When having a puncture, the patched tube becomes your new spare tube and the old spare tube becomes an actively used tube. Then only in the very unlucky case that you have two punctures per day, you need to use a patched tube without letting it wait for a day.

If you use a patched tube without letting it wait for a day, it may develop a slow leak. In the very unlucky case of two punctures in a single day, it will most likely allow you to reach home, but then you should ideally throw away the too-soon-used patched tube, or if you want to attempt to save some money, you could of course inspect how well it retains air (after letting it rest for a day, of course). Chances are it has a slow leak.

Of course all that applies assuming your rim and rim tape are ok. A damaged rim or an improperly installed and/or too narrow and/or rated for too low pressures rim tape can cause punctures too. In this case, you should fix the real culprit instead of continuing to patch a neverending stream of inner tubes.